How to build an Indoor Positioning System using ESP32 and Qorvo DWM3000 UWB Modules

#include <SPI.h>
#include <WiFi.h>
#include <WiFiClient.h>

// WiFi Configuration
const char *ssid = "Sxxxxxx";
const char *password = "cxxxxxxxxx";
const char *host = "192.168.xx.xx"; // Your PC's IP address
const int port = 7007;             // Choose a port number
WiFiClient client;
bool wifiConnected = false;

// SPI Setup
#define RST_PIN 27
#define CHIP_SELECT_PIN 4

// Scalable Anchor Configuration
#define NUM_ANCHORS 3 // Change this to scale the system
#define TAG_ID 10
#define FIRST_ANCHOR_ID 1 // Starting ID for anchors (1, 2, 3, ...)

// Ranging Configuration
#define FILTER_SIZE 50 // For median filter
#define MIN_DISTANCE 0
#define MAX_DISTANCE 10000.0

// UWB Configuration
#define LEN_RX_CAL_CONF 4
#define LEN_TX_FCTRL_CONF 6
#define LEN_AON_DIG_CFG_CONF 3
#define PMSC_STATE_IDLE 0x3
#define FCS_LEN 2
#define STDRD_SYS_CONFIG 0x188
#define DTUNE0_CONFIG 0x0F
#define SYS_STATUS_FRAME_RX_SUCC 0x2000
#define SYS_STATUS_RX_ERR 0x4279000
#define SYS_STATUS_FRAME_TX_SUCC 0x80
#define PREAMBLE_32 4
#define PREAMBLE_64 8
#define PREAMBLE_128 5
#define PREAMBLE_256 9
#define PREAMBLE_512 11
#define PREAMBLE_1024 2
#define PREAMBLE_2048 10
#define PREAMBLE_4096 3
#define PREAMBLE_1536 6
#define CHANNEL_5 0x0
#define CHANNEL_9 0x1
#define PAC4 0x03
#define PAC8 0x00
#define PAC16 0x01
#define PAC32 0x02
#define DATARATE_6_8MB 0x1
#define DATARATE_850KB 0x0
#define PHR_MODE_STANDARD 0x0
#define PHR_MODE_LONG 0x1
#define PHR_RATE_6_8MB 0x1
#define PHR_RATE_850KB 0x0
#define SPIRDY_MASK 0x80
#define RCINIT_MASK 0x100
#define BIAS_CTRL_BIAS_MASK 0x1F
#define GEN_CFG_AES_LOW_REG 0x00
#define GEN_CFG_AES_HIGH_REG 0x01
#define STS_CFG_REG 0x2
#define RX_TUNE_REG 0x3
#define EXT_SYNC_REG 0x4
#define GPIO_CTRL_REG 0x5
#define DRX_REG 0x6
#define RF_CONF_REG 0x7
#define RF_CAL_REG 0x8
#define FS_CTRL_REG 0x9
#define AON_REG 0xA
#define OTP_IF_REG 0xB
#define CIA_REG1 0xC
#define CIA_REG2 0xD
#define CIA_REG3 0xE
#define DIG_DIAG_REG 0xF
#define PMSC_REG 0x11
#define RX_BUFFER_0_REG 0x12
#define RX_BUFFER_1_REG 0x13
#define TX_BUFFER_REG 0x14
#define ACC_MEM_REG 0x15
#define SCRATCH_RAM_REG 0x16
#define AES_RAM_REG 0x17
#define SET_1_2_REG 0x18
#define INDIRECT_PTR_A_REG 0x1D
#define INDIRECT_PTR_B_REG 0x1E
#define IN_PTR_CFG_REG 0x1F
#define TRANSMIT_DELAY 0x3B9ACA00
#define TRANSMIT_DIFF 0x1FF
#define NS_UNIT 4.0064102564102564    // ns
#define PS_UNIT 15.6500400641025641   // ps
#define SPEED_OF_LIGHT 0.029979245800 // in centimetres per picosecond
#define CLOCK_OFFSET_CHAN_5_CONSTANT -0.5731e-3f
#define CLOCK_OFFSET_CHAN_9_CONSTANT -0.1252e-3f
#define NO_OFFSET 0x0
#define DEBUG_OUTPUT 0
static int ANTENNA_DELAY = 16350;
int led_status = 0;
int destination = 0x0;
int sender = 0x0;

// Initial Radio Configuration
int config[] = {
   CHANNEL_5,         // Channel
   PREAMBLE_128,      // Preamble Length
   9,                 // Preamble Code (Same for RX and TX!)
   PAC8,              // PAC
   DATARATE_6_8MB,    // Datarate
   PHR_MODE_STANDARD, // PHR Mode
   PHR_RATE_850KB     // PHR Rate
};

// Global variables
static int rx_status;
static int tx_status;
static int current_anchor_index = 0; // Index into anchors array
static int curr_stage = 0;

// Anchor data structure
struct AnchorData
{
   int anchor_id; // Anchor ID

   // Timing measurements
   int t_roundA = 0;
   int t_replyA = 0;
   long long rx = 0;
   long long tx = 0;
   int clock_offset = 0;

   // Distance measurements
   float distance = 0;
   float distance_history[FILTER_SIZE] = {0};
   int history_index = 0;
   float filtered_distance = 0;

   // Signal quality metrics
   float signal_strength = 0;    // RSSI in dBm
   float fp_signal_strength = 0; // First Path RSSI in dBm
};

// Dynamic array of anchor data
AnchorData anchors[NUM_ANCHORS];

// Helper functions for anchor management
void initializeAnchors()
{
   for (int i = 0; i < NUM_ANCHORS; i++)
   {
       anchors[i].anchor_id = FIRST_ANCHOR_ID + i;
       // Initialize all other fields to zero (default constructor handles this)
   }
}

AnchorData *getCurrentAnchor()
{
   return &anchors[current_anchor_index];
}

int getCurrentAnchorId()
{
   return anchors[current_anchor_index].anchor_id;
}

void switchToNextAnchor()
{
   current_anchor_index = (current_anchor_index + 1) % NUM_ANCHORS;
}

bool allAnchorsHaveValidData()
{
   for (int i = 0; i < NUM_ANCHORS; i++)
   {
       if (anchors[i].filtered_distance <= 0)
       {
           return false;
       }
   }
   return true;
}

class DWM3000Class
{
public:
   // Chip Setup
   static void spiSelect(uint8_t cs);
   static void begin();
   static void init();
   static void writeSysConfig();
   static void configureAsTX();
   static void setupGPIO();

   // Double-Sided Ranging
   static void ds_sendFrame(int stage);
   static void ds_sendRTInfo(int t_roundB, int t_replyB);
   static int ds_processRTInfo(int t_roundA, int t_replyA, int t_roundB, int t_replyB, int clock_offset);
   static int ds_getStage();
   static bool ds_isErrorFrame();
   static void ds_sendErrorFrame();

   // Radio Settings
   static void setChannel(uint8_t data);
   static void setPreambleLength(uint8_t data);
   static void setPreambleCode(uint8_t data);
   static void setPACSize(uint8_t data);
   static void setDatarate(uint8_t data);
   static void setPHRMode(uint8_t data);
   static void setPHRRate(uint8_t data);

   // Protocol Settings
   static void setMode(int mode);
   static void setTXFrame(unsigned long long frame_data);
   static void setFrameLength(int frame_len);
   static void setTXAntennaDelay(int delay);
   static void setSenderID(int senderID);
   static void setDestinationID(int destID);

   // Status Checks
   static int receivedFrameSucc();
   static int sentFrameSucc();
   static int getSenderID();
   static int getDestinationID();
   static bool checkForIDLE();
   static bool checkSPI();

   // Radio Analytics
   static double getSignalStrength();
   static double getFirstPathSignalStrength();
   static int getTXAntennaDelay();
   static long double getClockOffset();
   static long double getClockOffset(int32_t ext_clock_offset);
   static int getRawClockOffset();
   static float getTempInC();
   static unsigned long long readRXTimestamp();
   static unsigned long long readTXTimestamp();

   // Chip Interaction
   static uint32_t write(int base, int sub, uint32_t data, int data_len);
   static uint32_t write(int base, int sub, uint32_t data);
   static uint32_t read(int base, int sub);
   static uint8_t read8bit(int base, int sub);
   static uint32_t readOTP(uint8_t addr);

   // Delayed Sending Settings
   static void writeTXDelay(uint32_t delay);
   static void prepareDelayedTX();

   // Radio Stage Settings / Transfer and Receive Modes
   static void delayedTXThenRX();
   static void delayedTX();
   static void standardTX();
   static void standardRX();
   static void TXInstantRX();

   // DWM3000 Firmware Interaction
   static void softReset();
   static void hardReset();
   static void clearSystemStatus();

   // Hardware Status Information
   static void pullLEDHigh(int led);
   static void pullLEDLow(int led);

   // Calculation and Conversion
   static double convertToCM(int DWM3000_ps_units);
   static void calculateTXRXdiff();

   // Printing
   static void printRoundTripInformation();
   static void printDouble(double val, unsigned int precision, bool linebreak);

private:
   // Single Bit Settings
   static void setBit(int reg_addr, int sub_addr, int shift, bool b);
   static void setBitLow(int reg_addr, int sub_addr, int shift);
   static void setBitHigh(int reg_addr, int sub_addr, int shift);

   // Fast Commands
   static void writeFastCommand(int cmd);

   // SPI Interaction
   static uint32_t readOrWriteFullAddress(uint32_t base, uint32_t sub, uint32_t data, uint32_t data_len, uint32_t readWriteBit);
   static uint32_t sendBytes(int b[], int lenB, int recLen);

   // Soft Reset Helper Method
   static void clearAONConfig();

   // Other Helper Methods
   static unsigned int countBits(unsigned int number);
   static int checkForDevID();
};

DWM3000Class DWM3000;

// WiFi Functions
void connectToWiFi()
{
   Serial.println("Connecting to WiFi...");
   WiFi.begin(ssid, password);

   int attempts = 0;
   while (WiFi.status() != WL_CONNECTED && attempts < 20)
   {
       delay(500);
       Serial.print(".");
       attempts++;
   }

   if (WiFi.status() == WL_CONNECTED)
   {
       wifiConnected = true;
       Serial.println("\nWiFi connected");
       Serial.print("IP address: ");
       Serial.println(WiFi.localIP());
   }
   else
   {
       Serial.println("\nFailed to connect to WiFi");
   }
}

void sendDataOverWiFi()
{
   if (!wifiConnected)
   {
       connectToWiFi();
       if (!wifiConnected)
           return;
   }

   if (!client.connected())
   {
       if (!client.connect(host, port))
       {
           Serial.println("Connection to host failed");
           wifiConnected = false;
           return;
       }
   }

   // Create JSON structure dynamically based on number of anchors
   String data = "{\"tag_id\":" + String(TAG_ID) + ",\"anchors\":{";

   for (int i = 0; i < NUM_ANCHORS; i++)
   {
       data += "\"A" + String(anchors[i].anchor_id) + "\":{";
       data += "\"distance\":" + String(anchors[i].filtered_distance, 2) + ",";
       data += "\"raw\":" + String(anchors[i].distance, 2) + ",";
       data += "\"rssi\":" + String(anchors[i].signal_strength, 2) + ",";
       data += "\"fp_rssi\":" + String(anchors[i].fp_signal_strength, 2) + ",";
       data += "\"round_time\":" + String(anchors[i].t_roundA) + ",";
       data += "\"reply_time\":" + String(anchors[i].t_replyA) + ",";
       data += "\"clock_offset\":" + String((double)DWM3000.getClockOffset(anchors[i].clock_offset), 6);
       data += "}";

       // Add comma if not the last anchor
       if (i < NUM_ANCHORS - 1)
       {
           data += ",";
       }
   }

   data += "}}\n";

   client.print(data);

   // For debugging, print the JSON to serial
   Serial.println("Sent JSON data:");
   Serial.println(data);
}

// Helper function to validate distance
bool isValidDistance(float distance)
{
   return (distance >= MIN_DISTANCE && distance <= MAX_DISTANCE);
}

float calculateMedian(float arr[], int size)
{
   float temp[size];
   for (int i = 0; i < size; i++)
   {
       temp[i] = arr[i];
   }

   for (int i = 0; i < size - 1; i++)
   {
       for (int j = i + 1; j < size; j++)
       {
           if (temp[j] < temp[i])
           {
               float t = temp[i];
               temp[i] = temp[j];
               temp[j] = t;
           }
       }
   }

   if (size % 2 == 0)
   {
       return (temp[size / 2 - 1] + temp[size / 2]) / 2.0;
   }
   else
   {
       return temp[size / 2];
   }
}

// updateFilteredDistance function
void updateFilteredDistance(AnchorData &data)
{
   data.distance_history[data.history_index] = data.distance;
   data.history_index = (data.history_index + 1) % FILTER_SIZE;

   float valid_distances[FILTER_SIZE];
   int valid_count = 0;

   for (int i = 0; i < FILTER_SIZE; i++)
   {
       if (isValidDistance(data.distance_history[i]))
       {
           valid_distances[valid_count++] = data.distance_history[i];
       }
   }

   if (valid_count > 0)
   {
       data.filtered_distance = calculateMedian(valid_distances, valid_count);
   }
   else
   {
       data.filtered_distance = 0;
   }
}

// Debug print function
void printDebugInfo(int anchor, long long rx, long long tx, int t_round, int t_reply, int clock_offset)
{
   Serial.print("Anchor ");
   Serial.print(anchor);
   Serial.println(" Debug Info:");
   Serial.print("RX timestamp: ");
   Serial.println(rx);
   Serial.print("TX timestamp: ");
   Serial.println(tx);
   Serial.print("t_round: ");
   Serial.println(t_round);
   Serial.print("t_reply: ");
   Serial.println(t_reply);
   Serial.print("Clock offset: ");
   Serial.println(clock_offset);

   int ranging_time = DWM3000.ds_processRTInfo(t_round, t_reply,
                                               DWM3000.read(0x12, 0x04), DWM3000.read(0x12, 0x08), clock_offset);
   Serial.print("Calculated distance: ");
   Serial.println(DWM3000.convertToCM(ranging_time));
}

void printAllDistances()
{
   Serial.print("Distances - ");
   for (int i = 0; i < NUM_ANCHORS; i++)
   {
       Serial.print("A");
       Serial.print(anchors[i].anchor_id);
       Serial.print(": ");
       if (anchors[i].filtered_distance > 0)
       {
           DWM3000.printDouble(anchors[i].filtered_distance, 100, false);
           Serial.print(" cm");
       }
       else
       {
           Serial.print("INVALID");
       }

       if (i < NUM_ANCHORS - 1)
       {
           Serial.print(" | ");
       }
   }
   Serial.println();
}

// Implementation of DWM3000Class methods
void DWM3000Class::spiSelect(uint8_t cs)
{
   pinMode(cs, OUTPUT);
   digitalWrite(cs, HIGH);
   delay(5);
}

void DWM3000Class::begin()
{
   delay(5);
   pinMode(CHIP_SELECT_PIN, OUTPUT);
   SPI.begin();
   delay(5);
   spiSelect(CHIP_SELECT_PIN);
   Serial.println("[INFO] SPI ready");
}

void DWM3000Class::init()
{

   if (!checkForDevID())
   {
       Serial.println("[ERROR] Dev ID is wrong! Aborting!");
       return;
   }

   setBitHigh(GEN_CFG_AES_LOW_REG, 0x10, 4);

   while (!checkForIDLE())
   {
       Serial.println("[WARNING] IDLE FAILED (stage 1)");
       delay(100);
   }

   softReset();
   delay(200);

   while (!checkForIDLE())
   {
       Serial.println("[WARNING] IDLE FAILED (stage 2)");
       delay(100);
   }

   uint32_t ldo_low = readOTP(0x04);
   uint32_t ldo_high = readOTP(0x05);
   uint32_t bias_tune = readOTP(0xA);
   bias_tune = (bias_tune >> 16) & BIAS_CTRL_BIAS_MASK;

   if (ldo_low != 0 && ldo_high != 0 && bias_tune != 0)
   {
       write(0x11, 0x1F, bias_tune);
       write(0x0B, 0x08, 0x0100);
   }

   int xtrim_value = readOTP(0x1E);
   xtrim_value = xtrim_value == 0 ? 0x2E : xtrim_value;
   write(FS_CTRL_REG, 0x14, xtrim_value);
   if (DEBUG_OUTPUT)
       Serial.print("xtrim: ");
   if (DEBUG_OUTPUT)
       Serial.println(xtrim_value);

   writeSysConfig();
   write(0x00, 0x3C, 0xFFFFFFFF);
   write(0x00, 0x40, 0xFFFF);
   write(0x0A, 0x00, 0x000900, 3);

   write(0x3, 0x1C, 0x10000240);
   write(0x3, 0x20, 0x1B6DA489);
   write(0x3, 0x38, 0x0001C0FD);
   write(0x3, 0x3C, 0x0001C43E);
   write(0x3, 0x40, 0x0001C6BE);
   write(0x3, 0x44, 0x0001C77E);
   write(0x3, 0x48, 0x0001CF36);
   write(0x3, 0x4C, 0x0001CFB5);
   write(0x3, 0x50, 0x0001CFF5);
   write(0x3, 0x18, 0xE5E5);
   int f = read(0x4, 0x20);
   write(0x6, 0x0, 0x81101C);
   write(0x07, 0x34, 0x4);
   write(0x07, 0x48, 0x14);
   write(0x07, 0x1A, 0x0E);
   write(0x07, 0x1C, 0x1C071134);
   write(0x09, 0x00, 0x1F3C);
   write(0x09, 0x80, 0x81);
   write(0x11, 0x04, 0xB40200);
   write(0x11, 0x08, 0x80030738);
   Serial.println("[INFO] Initialization finished.\n");
}

void DWM3000Class::writeSysConfig()
{
   int usr_cfg = (STDRD_SYS_CONFIG & 0xFFF) | (config[5] << 3) | (config[6] << 4);
   write(GEN_CFG_AES_LOW_REG, 0x10, usr_cfg);

   if (config[2] > 24)
   {
       Serial.println("[ERROR] SCP ERROR! TX & RX Preamble Code higher than 24!");
   }

   int otp_write = 0x1400;
   if (config[1] >= 256)
   {
       otp_write |= 0x04;
   }

   write(OTP_IF_REG, 0x08, otp_write);
   write(DRX_REG, 0x00, 0x00, 1);
   write(DRX_REG, 0x0, config[3]);
   write(STS_CFG_REG, 0x0, 64 / 8 - 1);
   write(GEN_CFG_AES_LOW_REG, 0x29, 0x00, 1);
   write(DRX_REG, 0x0C, 0xAF5F584C);

   int chan_ctrl_val = read(GEN_CFG_AES_HIGH_REG, 0x14);
   chan_ctrl_val &= (~0x1FFF);
   chan_ctrl_val |= config[0];
   chan_ctrl_val |= 0x1F00 & (config[2] << 8);
   chan_ctrl_val |= 0xF8 & (config[2] << 3);
   chan_ctrl_val |= 0x06 & (0x01 << 1);
   write(GEN_CFG_AES_HIGH_REG, 0x14, chan_ctrl_val);

   int tx_fctrl_val = read(GEN_CFG_AES_LOW_REG, 0x24);
   tx_fctrl_val |= (config[1] << 12);
   tx_fctrl_val |= (config[4] << 10);
   write(GEN_CFG_AES_LOW_REG, 0x24, tx_fctrl_val);
   write(DRX_REG, 0x02, 0x81);

   int rf_tx_ctrl_2 = 0x1C071134;
   int pll_conf = 0x0F3C;
   if (config[0])
   {
       rf_tx_ctrl_2 &= ~0x00FFFF;
       rf_tx_ctrl_2 |= 0x000001;
       pll_conf &= 0x00FF;
       pll_conf |= 0x001F;
   }

   write(RF_CONF_REG, 0x1C, rf_tx_ctrl_2);
   write(FS_CTRL_REG, 0x00, pll_conf);
   write(RF_CONF_REG, 0x51, 0x14);
   write(RF_CONF_REG, 0x1A, 0x0E);
   write(FS_CTRL_REG, 0x08, 0x81);
   write(GEN_CFG_AES_LOW_REG, 0x44, 0x02);
   write(PMSC_REG, 0x04, 0x300200);
   write(PMSC_REG, 0x08, 0x0138);

   int success = 0;
   for (int i = 0; i < 100; i++)
   {
       if (read(GEN_CFG_AES_LOW_REG, 0x0) & 0x2)
       {
           success = 1;
           break;
       }
   }

   if (!success)
   {
       Serial.println("[ERROR] Couldn't lock PLL Clock!");
   }
   else
   {
       Serial.println("[INFO] PLL is now locked.");
   }

   int otp_val = read(OTP_IF_REG, 0x08);
   otp_val |= 0x40;
   if (config[0])
       otp_val |= 0x2000;
   write(OTP_IF_REG, 0x08, otp_val);
   write(RX_TUNE_REG, 0x19, 0xF0);

   int ldo_ctrl_val = read(RF_CONF_REG, 0x48);
   int tmp_ldo = (0x105 | 0x100 | 0x4 | 0x1);
   write(RF_CONF_REG, 0x48, tmp_ldo);
   write(EXT_SYNC_REG, 0x0C, 0x020000);
   int l = read(0x04, 0x0C);
   delay(20);
   write(EXT_SYNC_REG, 0x0C, 0x11);

   int succ = 0;
   for (int i = 0; i < 100; i++)
   {
       if (read(EXT_SYNC_REG, 0x20))
       {
           succ = 1;
           break;
       }
       delay(10);
   }

   if (succ)
   {
       Serial.println("[INFO] PGF calibration complete.");
   }
   else
   {
       Serial.println("[ERROR] PGF calibration failed!");
   }

   write(EXT_SYNC_REG, 0x0C, 0x00);
   write(EXT_SYNC_REG, 0x20, 0x01);

   int rx_cal_res = read(EXT_SYNC_REG, 0x14);
   if (rx_cal_res == 0x1fffffff)
   {
       Serial.println("[ERROR] PGF_CAL failed in stage I!");
   }
   rx_cal_res = read(EXT_SYNC_REG, 0x1C);
   if (rx_cal_res == 0x1fffffff)
   {
       Serial.println("[ERROR] PGF_CAL failed in stage Q!");
   }

   write(RF_CONF_REG, 0x48, ldo_ctrl_val);
   write(0x0E, 0x02, 0x01);
   setTXAntennaDelay(ANTENNA_DELAY);
}

void DWM3000Class::configureAsTX()
{
   write(RF_CONF_REG, 0x1C, 0x34);
   write(GEN_CFG_AES_HIGH_REG, 0x0C, 0xFDFDFDFD);
}

void DWM3000Class::setupGPIO()
{
   write(0x05, 0x08, 0xF0);
}

void DWM3000Class::ds_sendFrame(int stage)
{
   setMode(1);
   write(0x14, 0x01, sender & 0xFF);
   write(0x14, 0x02, destination & 0xFF);
   write(0x14, 0x03, stage & 0x7);
   setFrameLength(4);
   TXInstantRX();

   bool error = true;
   for (int i = 0; i < 50; i++)
   {
       if (sentFrameSucc())
       {
           error = false;
           break;
       }
   };
   if (error)
   {
       Serial.println("[ERROR] Could not send frame successfully!");
   }
}

void DWM3000Class::ds_sendRTInfo(int t_roundB, int t_replyB)
{
   setMode(1);
   write(0x14, 0x01, destination & 0xFF);
   write(0x14, 0x02, sender & 0xFF);
   write(0x14, 0x03, 4);
   write(0x14, 0x04, t_roundB);
   write(0x14, 0x08, t_replyB);
   setFrameLength(12);
   TXInstantRX();
}

int DWM3000Class::ds_processRTInfo(int t_roundA, int t_replyA, int t_roundB, int t_replyB, int clk_offset)
{
   if (DEBUG_OUTPUT)
   {
       Serial.println("\nProcessing Information:");
       Serial.print("t_roundA: ");
       Serial.println(t_roundA);
       Serial.print("t_replyA: ");
       Serial.println(t_replyA);
       Serial.print("t_roundB: ");
       Serial.println(t_roundB);
       Serial.print("t_replyB: ");
       Serial.println(t_replyB);
   }

   int reply_diff = t_replyA - t_replyB;
   long double clock_offset = t_replyA > t_replyB ? 1.0 + getClockOffset(clk_offset) : 1.0 - getClockOffset(clk_offset);
   int first_rt = t_roundA - t_replyB;
   int second_rt = t_roundB - t_replyA;
   int combined_rt = (first_rt + second_rt - (reply_diff - (reply_diff * clock_offset))) / 2;
   int combined_rt_raw = (first_rt + second_rt) / 2;
   return combined_rt / 2;
}

int DWM3000Class::ds_getStage()
{
   return read(0x12, 0x03) & 0b111;
}

bool DWM3000Class::ds_isErrorFrame()
{
   return ((read(0x12, 0x00) & 0x7) == 7);
}

void DWM3000Class::ds_sendErrorFrame()
{
   Serial.println("[WARNING] Error Frame sent. Reverting back to stage 0.");
   setMode(7);
   setFrameLength(3);
   standardTX();
}

void DWM3000Class::setChannel(uint8_t data)
{
   if (data == CHANNEL_5 || data == CHANNEL_9)
       config[0] = data;
}

void DWM3000Class::setPreambleLength(uint8_t data)
{
   if (data == PREAMBLE_32 || data == PREAMBLE_64 || data == PREAMBLE_1024 || data == PREAMBLE_256 || data == PREAMBLE_512 || data == PREAMBLE_1024 || data == PREAMBLE_1536 || data == PREAMBLE_2048 || data == PREAMBLE_4096)
       config[1] = data;
}

void DWM3000Class::setPreambleCode(uint8_t data)
{
   if (data <= 12 && data >= 9)
       config[2] = data;
}

void DWM3000Class::setPACSize(uint8_t data)
{
   if (data == PAC4 || data == PAC8 || data == PAC16 || data == PAC32)
       config[3] = data;
}

void DWM3000Class::setDatarate(uint8_t data)
{
   if (data == DATARATE_6_8MB || data == DATARATE_850KB)
       config[4] = data;
}

void DWM3000Class::setPHRMode(uint8_t data)
{
   if (data == PHR_MODE_STANDARD || data == PHR_MODE_LONG)
       config[5] = data;
}

void DWM3000Class::setPHRRate(uint8_t data)
{
   if (data == PHR_RATE_6_8MB || data == PHR_RATE_850KB)
       config[6] = data;
}

void DWM3000Class::setMode(int mode)
{
   write(0x14, 0x00, mode & 0x7);
}

void DWM3000Class::setTXFrame(unsigned long long frame_data)
{
   if (frame_data > ((pow(2, 8 * 8) - FCS_LEN)))
   {
       Serial.println("[ERROR] Frame is too long (> 1023 Bytes - FCS_LEN)!");
       return;
   }
   write(TX_BUFFER_REG, 0x00, frame_data);
}

void DWM3000Class::setFrameLength(int frameLen)
{
   frameLen = frameLen + FCS_LEN;
   int curr_cfg = read(0x00, 0x24);
   if (frameLen > 1023)
   {
       Serial.println("[ERROR] Frame length + FCS_LEN (2) is longer than 1023. Aborting!");
       return;
   }
   int tmp_cfg = (curr_cfg & 0xFFFFFC00) | frameLen;
   write(GEN_CFG_AES_LOW_REG, 0x24, tmp_cfg);
}

void DWM3000Class::setTXAntennaDelay(int delay)
{
   ANTENNA_DELAY = delay;
   write(0x01, 0x04, delay);
}

void DWM3000Class::setSenderID(int senderID)
{
   sender = senderID;
}

void DWM3000Class::setDestinationID(int destID)
{
   destination = destID;
}

int DWM3000Class::receivedFrameSucc()
{
   int sys_stat = read(GEN_CFG_AES_LOW_REG, 0x44);
   if ((sys_stat & SYS_STATUS_FRAME_RX_SUCC) > 0)
   {
       return 1;
   }
   else if ((sys_stat & SYS_STATUS_RX_ERR) > 0)
   {
       return 2;
   }
   return 0;
}

int DWM3000Class::sentFrameSucc()
{
   int sys_stat = read(GEN_CFG_AES_LOW_REG, 0x44);
   if ((sys_stat & SYS_STATUS_FRAME_TX_SUCC) == SYS_STATUS_FRAME_TX_SUCC)
   {
       return 1;
   }
   return 0;
}

int DWM3000Class::getSenderID()
{
   return read(0x12, 0x01) & 0xFF;
}

int DWM3000Class::getDestinationID()
{
   return read(0x12, 0x02) & 0xFF;
}

bool DWM3000Class::checkForIDLE()
{
   return (read(0x0F, 0x30) >> 16 & PMSC_STATE_IDLE) == PMSC_STATE_IDLE || (read(0x00, 0x44) >> 16 & (SPIRDY_MASK | RCINIT_MASK)) == (SPIRDY_MASK | RCINIT_MASK) ? 1 : 0;
}

bool DWM3000Class::checkSPI()
{
   return checkForDevID();
}

double DWM3000Class::getSignalStrength()
{
   int CIRpower = read(0x0C, 0x2C) & 0x1FF;
   int PAC_val = read(0x0C, 0x58) & 0xFFF;
   unsigned int DGC_decision = (read(0x03, 0x60) >> 28) & 0x7;
   double PRF_const = 121.7;
   return 10 * log10((CIRpower * (1 << 21)) / pow(PAC_val, 2)) + (6 * DGC_decision) - PRF_const;
}

double DWM3000Class::getFirstPathSignalStrength()
{
   float f1 = (read(0x0C, 0x30) & 0x3FFFFF) >> 2;
   float f2 = (read(0x0C, 0x34) & 0x3FFFFF) >> 2;
   float f3 = (read(0x0C, 0x38) & 0x3FFFFF) >> 2;
   int PAC_val = read(0x0C, 0x58) & 0xFFF;
   unsigned int DGC_decision = (read(0x03, 0x60) >> 28) & 0x7;
   double PRF_const = 121.7;
   return 10 * log10((pow(f1, 2) + pow(f2, 2) + pow(f3, 2)) / pow(PAC_val, 2)) + (6 * DGC_decision) - PRF_const;
}

int DWM3000Class::getTXAntennaDelay()
{
   int delay = read(0x01, 0x04) & 0xFFFF;
   return delay;
}

long double DWM3000Class::getClockOffset()
{
   if (config[0] == CHANNEL_5)
   {
       return getRawClockOffset() * CLOCK_OFFSET_CHAN_5_CONSTANT / 1000000;
   }
   else
   {
       return getRawClockOffset() * CLOCK_OFFSET_CHAN_9_CONSTANT / 1000000;
   }
}

long double DWM3000Class::getClockOffset(int32_t sec_clock_offset)
{
   if (config[0] == CHANNEL_5)
   {
       return sec_clock_offset * CLOCK_OFFSET_CHAN_5_CONSTANT / 1000000;
   }
   else
   {
       return sec_clock_offset * CLOCK_OFFSET_CHAN_9_CONSTANT / 1000000;
   }
}

int DWM3000Class::getRawClockOffset()
{
   int raw_offset = read(0x06, 0x29) & 0x1FFFFF;
   if (raw_offset & (1 << 20))
   {
       raw_offset |= ~((1 << 21) - 1);
   }
   if (DEBUG_OUTPUT)
   {
       Serial.print("Raw offset: ");
       Serial.println(raw_offset);
   }
   return raw_offset;
}

float DWM3000Class::getTempInC()
{
   write(0x07, 0x34, 0x04);
   write(0x08, 0x00, 0x01);
   while (!(read(0x08, 0x04) & 0x01))
   {
   };
   int res = read(0x08, 0x08);
   res = (res & 0xFF00) >> 8;
   int otp_temp = readOTP(0x09) & 0xFF;
   float tmp = (float)((res - otp_temp) * 1.05f) + 22.0f;
   write(0x08, 0x00, 0x00, 1);
   return tmp;
}

unsigned long long DWM3000Class::readRXTimestamp()
{
   uint32_t ts_low = read(0x0C, 0x00);
   unsigned long long ts_high = read(0x0C, 0x04) & 0xFF;
   unsigned long long rx_timestamp = (ts_high << 32) | ts_low;
   return rx_timestamp;
}

unsigned long long DWM3000Class::readTXTimestamp()
{
   unsigned long long ts_low = read(0x00, 0x74);
   unsigned long long ts_high = read(0x00, 0x78) & 0xFF;
   unsigned long long tx_timestamp = (ts_high << 32) + ts_low;
   return tx_timestamp;
}

uint32_t DWM3000Class::write(int base, int sub, uint32_t data, int dataLen)
{
   return readOrWriteFullAddress(base, sub, data, dataLen, 1);
}

uint32_t DWM3000Class::write(int base, int sub, uint32_t data)
{
   return readOrWriteFullAddress(base, sub, data, 0, 1);
}

uint32_t DWM3000Class::read(int base, int sub)
{
   uint32_t tmp;
   tmp = readOrWriteFullAddress(base, sub, 0, 0, 0);
   if (DEBUG_OUTPUT)
       Serial.println("");
   return tmp;
}

uint8_t DWM3000Class::read8bit(int base, int sub)
{
   return (uint8_t)(read(base, sub) >> 24);
}

uint32_t DWM3000Class::readOTP(uint8_t addr)
{
   write(OTP_IF_REG, 0x04, addr);
   write(OTP_IF_REG, 0x08, 0x02);
   return read(OTP_IF_REG, 0x10);
}

void DWM3000Class::writeTXDelay(uint32_t delay)
{
   write(0x00, 0x2C, delay);
}

void DWM3000Class::prepareDelayedTX()
{
   long long rx_ts = readRXTimestamp();
   uint32_t exact_tx_timestamp = (long long)(rx_ts + TRANSMIT_DELAY) >> 8;
   long long calc_tx_timestamp = ((rx_ts + TRANSMIT_DELAY) & ~TRANSMIT_DIFF) + ANTENNA_DELAY;
   uint32_t reply_delay = calc_tx_timestamp - rx_ts;
   write(0x14, 0x01, sender & 0xFF);
   write(0x14, 0x02, destination & 0xFF);
   write(0x14, 0x03, reply_delay);
   setFrameLength(7);
   writeTXDelay(exact_tx_timestamp);
}

void DWM3000Class::delayedTXThenRX()
{
   writeFastCommand(0x0F);
}

void DWM3000Class::delayedTX()
{
   writeFastCommand(0x3);
}

void DWM3000Class::standardTX()
{
   writeFastCommand(0x01);
}

void DWM3000Class::standardRX()
{
   writeFastCommand(0x02);
}

void DWM3000Class::TXInstantRX()
{
   writeFastCommand(0x0C);
}

void DWM3000Class::softReset()
{
   clearAONConfig();
   write(PMSC_REG, 0x04, 0x1);
   write(PMSC_REG, 0x00, 0x00, 2);
   delay(100);
   write(PMSC_REG, 0x00, 0xFFFF);
   write(PMSC_REG, 0x04, 0x00, 1);
}

void DWM3000Class::hardReset()
{
   pinMode(RST_PIN, OUTPUT);
   digitalWrite(RST_PIN, LOW);
   delay(10);
   pinMode(RST_PIN, INPUT);
}

void DWM3000Class::clearSystemStatus()
{
   write(GEN_CFG_AES_LOW_REG, 0x44, 0x3F7FFFFF);
}

void DWM3000Class::pullLEDHigh(int led)
{
   if (led > 2)
       return;
   led_status = led_status | (1 << led);
   write(0x05, 0x0C, led_status);
}

void DWM3000Class::pullLEDLow(int led)
{
   if (led > 2)
       return;
   led_status = led_status & ~((int)1 << led);
   write(0x05, 0x0C, led_status);
}

double DWM3000Class::convertToCM(int DWM3000_ps_units)
{
   return (double)DWM3000_ps_units * PS_UNIT * SPEED_OF_LIGHT;
}

void DWM3000Class::calculateTXRXdiff()
{
   unsigned long long ping_tx = readTXTimestamp();
   unsigned long long ping_rx = readRXTimestamp();
   long double clk_offset = getClockOffset();
   long double clock_offset = 1.0 + clk_offset;
   long long t_reply = read(RX_BUFFER_0_REG, 0x03);

   if (t_reply == 0)
   {
       return;
   }

   long long t_round = ping_rx - ping_tx;
   long long t_prop = lround((t_round - lround(t_reply * clock_offset)) / 2);
   long double t_prop_ps = t_prop * PS_UNIT;
   long double t_prop_cm = t_prop_ps * SPEED_OF_LIGHT;
   if (t_prop_cm >= 0)
   {
       printDouble(t_prop_cm, 100, false);
       Serial.println("cm");
   }
}

void DWM3000Class::printRoundTripInformation()
{
   Serial.println("\nRound Trip Information:");
   long long tx_ts = readTXTimestamp();
   long long rx_ts = readRXTimestamp();
   Serial.print("TX Timestamp: ");
   Serial.println(tx_ts);
   Serial.print("RX Timestamp: ");
   Serial.println(rx_ts);
}

void DWM3000Class::printDouble(double val, unsigned int precision, bool linebreak)
{
   Serial.print(int(val));
   Serial.print(".");
   unsigned int frac;
   if (val >= 0)
   {
       frac = (val - int(val)) * precision;
   }
   else
   {
       frac = (int(val) - val) * precision;
   }
   if (linebreak)
   {
       Serial.println(frac, DEC);
   }
   else
   {
       Serial.print(frac, DEC);
   }
}

void DWM3000Class::setBit(int reg_addr, int sub_addr, int shift, bool b)
{
   uint8_t tmpByte = read8bit(reg_addr, sub_addr);
   if (b)
   {
       bitSet(tmpByte, shift);
   }
   else
   {
       bitClear(tmpByte, shift);
   }
   write(reg_addr, sub_addr, tmpByte);
}

void DWM3000Class::setBitLow(int reg_addr, int sub_addr, int shift)
{
   setBit(reg_addr, sub_addr, shift, 0);
}

void DWM3000Class::setBitHigh(int reg_addr, int sub_addr, int shift)
{
   setBit(reg_addr, sub_addr, shift, 1);
}

void DWM3000Class::writeFastCommand(int cmd)
{
   if (DEBUG_OUTPUT)
       Serial.print("[INFO] Executing short command: ");
   int header = 0;
   header = header | 0x1;
   header = header | (cmd & 0x1F) << 1;
   header = header | 0x80;
   if (DEBUG_OUTPUT)
       Serial.println(header, BIN);
   int header_arr[] = {header};
   sendBytes(header_arr, 1, 0);
}

uint32_t DWM3000Class::readOrWriteFullAddress(uint32_t base, uint32_t sub, uint32_t data, uint32_t dataLen, uint32_t readWriteBit)
{
   uint32_t header = 0x00;
   if (readWriteBit)
       header = header | 0x80;
   header = header | ((base & 0x1F) << 1);
   if (sub > 0)
   {
       header = header | 0x40;
       header = header << 8;
       header = header | ((sub & 0x7F) << 2);
   }
   uint32_t header_size = header > 0xFF ? 2 : 1;
   uint32_t res = 0;
   if (!readWriteBit)
   {
       int headerArr[header_size];
       if (header_size == 1)
       {
           headerArr[0] = header;
       }
       else
       {
           headerArr[0] = (header & 0xFF00) >> 8;
           headerArr[1] = header & 0xFF;
       }
       res = (uint32_t)sendBytes(headerArr, header_size, 4);
       return res;
   }
   else
   {
       uint32_t payload_bytes = 0;
       if (dataLen == 0)
       {
           if (data > 0)
           {
               uint32_t payload_bits = countBits(data);
               payload_bytes = (payload_bits - (payload_bits % 8)) / 8;
               if ((payload_bits % 8) > 0)
               {
                   payload_bytes++;
               }
           }
           else
           {
               payload_bytes = 1;
           }
       }
       else
       {
           payload_bytes = dataLen;
       }
       int payload[header_size + payload_bytes];
       if (header_size == 1)
       {
           payload[0] = header;
       }
       else
       {
           payload[0] = (header & 0xFF00) >> 8;
           payload[1] = header & 0xFF;
       }
       for (int i = 0; i < payload_bytes; i++)
       {
           payload[header_size + i] = (data >> i * 8) & 0xFF;
       }
       res = (uint32_t)sendBytes(payload, 2 + payload_bytes, 0);
       return res;
   }
}

uint32_t DWM3000Class::sendBytes(int b[], int lenB, int recLen)
{
   digitalWrite(CHIP_SELECT_PIN, LOW);
   for (int i = 0; i < lenB; i++)
   {
       SPI.transfer(b[i]);
   }
   int rec;
   uint32_t val, tmp;
   if (recLen > 0)
   {
       for (int i = 0; i < recLen; i++)
       {
           tmp = SPI.transfer(0x00);
           if (i == 0)
           {
               val = tmp;
           }
           else
           {
               val |= (uint32_t)tmp << 8 * i;
           }
       }
   }
   else
   {
       val = 0;
   }
   digitalWrite(CHIP_SELECT_PIN, HIGH);
   return val;
}

void DWM3000Class::clearAONConfig()
{
   write(AON_REG, NO_OFFSET, 0x00, 2);
   write(AON_REG, 0x14, 0x00, 1);
   write(AON_REG, 0x04, 0x00, 1);
   write(AON_REG, 0x04, 0x02);
   delay(1);
}

unsigned int DWM3000Class::countBits(unsigned int number)
{
   return (int)log2(number) + 1;
}

int DWM3000Class::checkForDevID()
{
   int res = read(GEN_CFG_AES_LOW_REG, NO_OFFSET);
   if (res != 0xDECA0302 && res != 0xDECA0312)
   {
       Serial.println("[ERROR] DEV_ID IS WRONG!");
       return 0;
   }
   return 1;
}

void setup()
{
   Serial.begin(115200);
   // Initialize anchor array
   initializeAnchors();

   Serial.print("Initialized ");
   Serial.print(NUM_ANCHORS);
   Serial.println(" anchors:");
   for (int i = 0; i < NUM_ANCHORS; i++)
   {
       Serial.print("  Anchor ");
       Serial.print(i);
       Serial.print(" - ID: ");
       Serial.println(anchors[i].anchor_id);
   }

   // Connect to WiFi first
   connectToWiFi();

   // Initialize UWB
   DWM3000.begin();
   DWM3000.hardReset();
   delay(200);

   if (!DWM3000.checkSPI())
   {
       Serial.println("[ERROR] Could not establish SPI Connection to DWM3000!");
       while (1)
           ;
   }

   while (!DWM3000.checkForIDLE())
   {
       Serial.println("[ERROR] IDLE1 FAILED\r");
       delay(1000);
   }

   DWM3000.softReset();
   delay(200);

   if (!DWM3000.checkForIDLE())
   {
       Serial.println("[ERROR] IDLE2 FAILED\r");
       while (1)
           ;
   }

   DWM3000.init();
   DWM3000.setupGPIO();
   DWM3000.setTXAntennaDelay(16350);
   DWM3000.setSenderID(TAG_ID);

   Serial.println("> TAG - Three Anchor Ranging System <");
   Serial.println("> With WiFi Communication <\n");
   Serial.println("[INFO] Setup is finished.");
   Serial.print("Antenna delay set to: ");
   Serial.println(DWM3000.getTXAntennaDelay());

   DWM3000.configureAsTX();
   DWM3000.clearSystemStatus();
}

void loop()
{
   AnchorData *currentAnchor = getCurrentAnchor();
   int currentAnchorId = getCurrentAnchorId();

   switch (curr_stage)
   {
   case 0: // Start ranging with current target
       // Reset timing measurements for current anchor
       currentAnchor->t_roundA = 0;
       currentAnchor->t_replyA = 0;

       DWM3000.setDestinationID(currentAnchorId);
       DWM3000.ds_sendFrame(1);
       currentAnchor->tx = DWM3000.readTXTimestamp();
       curr_stage = 1;
       break;

   case 1: // Await first response
       if (rx_status = DWM3000.receivedFrameSucc())
       {
           DWM3000.clearSystemStatus();
           if (rx_status == 1)
           {
               if (DWM3000.ds_isErrorFrame())
               {
                   Serial.print("[WARNING] Error frame from Anchor ");
                   Serial.print(currentAnchorId);
                   Serial.print("! Signal strength: ");
                   Serial.print(DWM3000.getSignalStrength());
                   Serial.println(" dBm");
                   curr_stage = 0;
               }
               else if (DWM3000.ds_getStage() != 2)
               {
                   Serial.print("[WARNING] Unexpected stage from Anchor ");
                   Serial.print(currentAnchorId);
                   Serial.print(": ");
                   Serial.println(DWM3000.ds_getStage());
                   DWM3000.ds_sendErrorFrame();
                   curr_stage = 0;
               }
               else
               {
                   curr_stage = 2;
               }
           }
           else
           {
               Serial.print("[ERROR] Receiver Error from Anchor ");
               Serial.println(currentAnchorId);
               DWM3000.clearSystemStatus();
           }
       }
       break;

   case 2: // Response received. Send second ranging
       currentAnchor->rx = DWM3000.readRXTimestamp();
       DWM3000.ds_sendFrame(3);

       currentAnchor->t_roundA = currentAnchor->rx - currentAnchor->tx;
       currentAnchor->tx = DWM3000.readTXTimestamp();
       currentAnchor->t_replyA = currentAnchor->tx - currentAnchor->rx;

       curr_stage = 3;
       break;

   case 3: // Await second response
       if (rx_status = DWM3000.receivedFrameSucc())
       {
           DWM3000.clearSystemStatus();
           if (rx_status == 1)
           {
               if (DWM3000.ds_isErrorFrame())
               {
                   Serial.print("[WARNING] Error frame from Anchor ");
                   Serial.println(currentAnchorId);
                   curr_stage = 0;
               }
               else
               {
                   currentAnchor->clock_offset = DWM3000.getRawClockOffset();
                   curr_stage = 4;
               }
           }
           else
           {
               Serial.print("[ERROR] Receiver Error from Anchor ");
               Serial.println(currentAnchorId);
               DWM3000.clearSystemStatus();
           }
       }
       break;

   case 4: // Response received. Calculating results
   {
       int ranging_time = DWM3000.ds_processRTInfo(
           currentAnchor->t_roundA,
           currentAnchor->t_replyA,
           DWM3000.read(0x12, 0x04),
           DWM3000.read(0x12, 0x08),
           currentAnchor->clock_offset);

       currentAnchor->distance = DWM3000.convertToCM(ranging_time);
       currentAnchor->signal_strength = DWM3000.getSignalStrength();
       currentAnchor->fp_signal_strength = DWM3000.getFirstPathSignalStrength();
       updateFilteredDistance(*currentAnchor);
   }

       // Print current distances
       printAllDistances();

       // Send data over WiFi if all anchors have valid data
       if (allAnchorsHaveValidData())
       {
           sendDataOverWiFi();
       }

       // Switch to next anchor
       switchToNextAnchor();
       curr_stage = 0;
       break;

   default:
       Serial.print("Entered stage (");
       Serial.print(curr_stage);
       Serial.println("). Reverting back to stage 0");
       curr_stage = 0;
       break;
   }
}
 
Anchor Full Code:
#include <Arduino.h>
#include <SPI.h>
// SPI Setup
#define RST_PIN 27
#define CHIP_SELECT_PIN 4

// Set to 1 for Anchor 1, 2 for Anchor 2
#define ANCHOR_ID 1
#define RESPONSE_TIMEOUT_MS 10 // Maximum time to wait for a response
unsigned long last_ranging_time = 0;
#define MAX_RETRIES 3
int retry_count = 0;

static int rx_status;
static int tx_status;

static int curr_stage = 0;

static int t_roundB = 0;
static int t_replyB = 0;

static long long rx = 0;
static long long tx = 0;

#define LEN_RX_CAL_CONF 4
#define LEN_TX_FCTRL_CONF 6
#define LEN_AON_DIG_CFG_CONF 3

#define PMSC_STATE_IDLE 0x3

#define FCS_LEN 2

#define STDRD_SYS_CONFIG 0x188
#define DTUNE0_CONFIG 0x0F

#define SYS_STATUS_FRAME_RX_SUCC 0x2000
#define SYS_STATUS_RX_ERR 0x4279000

#define SYS_STATUS_FRAME_TX_SUCC 0x80

#define PREAMBLE_32 4
#define PREAMBLE_64 8
#define PREAMBLE_128 5
#define PREAMBLE_256 9
#define PREAMBLE_512 11
#define PREAMBLE_1024 2
#define PREAMBLE_2048 10
#define PREAMBLE_4096 3
#define PREAMBLE_1536 6

#define CHANNEL_5 0x0
#define CHANNEL_9 0x1

#define PAC4 0x03
#define PAC8 0x00
#define PAC16 0x01
#define PAC32 0x02

#define DATARATE_6_8MB 0x1
#define DATARATE_850KB 0x0

#define PHR_MODE_STANDARD 0x0
#define PHR_MODE_LONG 0x1

#define PHR_RATE_6_8MB 0x1
#define PHR_RATE_850KB 0x0

// Masks
#define SPIRDY_MASK 0x80
#define RCINIT_MASK 0x100
#define BIAS_CTRL_BIAS_MASK 0x1F

// Registers
#define GEN_CFG_AES_LOW_REG 0x00
#define GEN_CFG_AES_HIGH_REG 0x01
#define STS_CFG_REG 0x2
#define RX_TUNE_REG 0x3
#define EXT_SYNC_REG 0x4
#define GPIO_CTRL_REG 0x5
#define DRX_REG 0x6
#define RF_CONF_REG 0x7
#define RF_CAL_REG 0x8
#define FS_CTRL_REG 0x9
#define AON_REG 0xA
#define OTP_IF_REG 0xB
#define CIA_REG1 0xC
#define CIA_REG2 0xD
#define CIA_REG3 0xE
#define DIG_DIAG_REG 0xF
#define PMSC_REG 0x11
#define RX_BUFFER_0_REG 0x12
#define RX_BUFFER_1_REG 0x13
#define TX_BUFFER_REG 0x14
#define ACC_MEM_REG 0x15
#define SCRATCH_RAM_REG 0x16
#define AES_RAM_REG 0x17
#define SET_1_2_REG 0x18
#define INDIRECT_PTR_A_REG 0x1D
#define INDIRECT_PTR_B_REG 0x1E
#define IN_PTR_CFG_REG 0x1F

#define TRANSMIT_DELAY 0x3B9ACA00 // //0x77359400

#define TRANSMIT_DIFF 0x1FF

#define NS_UNIT 4.0064102564102564  // ns
#define PS_UNIT 15.6500400641025641 // ps

#define SPEED_OF_LIGHT 0.029979245800 // in centimetres per picosecond

#define CLOCK_OFFSET_CHAN_5_CONSTANT -0.5731e-3f
#define CLOCK_OFFSET_CHAN_9_CONSTANT -0.1252e-3f

// Offsets
#define NO_OFFSET 0x0

#define DEBUG_OUTPUT 0 // Turn to 1 to get all reads, writes, etc. as info in the console
static int ANTENNA_DELAY = 16350;

int led_status = 0;

int destination = 0x0; // Default Values for Destination and Sender IDs
int sender = 0x0;

class DWM3000Class
{
public:
 static int config[9];

 // Chip Setup
 static void spiSelect(uint8_t cs);

 static void begin();
 static void init();

 static void writeSysConfig();
 static void configureAsTX();
 static void setupGPIO();

 // Double-Sided Ranging
 static void ds_sendFrame(int stage);
 static void ds_sendRTInfo(int t_roundB, int t_replyB);
 static int ds_processRTInfo(int t_roundA, int t_replyA, int t_roundB, int t_replyB, int clock_offset);
 static int ds_getStage();
 static bool ds_isErrorFrame();
 static void ds_sendErrorFrame();

 // Radio Settings
 static void setChannel(uint8_t data);
 static void setPreambleLength(uint8_t data);
 static void setPreambleCode(uint8_t data);
 static void setPACSize(uint8_t data);
 static void setDatarate(uint8_t data);
 static void setPHRMode(uint8_t data);
 static void setPHRRate(uint8_t data);

 // Protocol Settings
 static void setMode(int mode);
 static void setTXFrame(unsigned long long frame_data);
 static void setFrameLength(int frame_len);
 static void setTXAntennaDelay(int delay);
 static void setSenderID(int senderID);
 static void setDestinationID(int destID);

 // Status Checks
 static int receivedFrameSucc();
 static int sentFrameSucc();
 static int getSenderID();
 static int getDestinationID();
 static bool checkForIDLE();
 static bool checkSPI();

 // Radio Analytics
 static double getSignalStrength();
 static double getFirstPathSignalStrength();
 static int getTXAntennaDelay();
 static long double getClockOffset();
 static long double getClockOffset(int32_t ext_clock_offset);
 static int getRawClockOffset();
 static float getTempInC();

 static unsigned long long readRXTimestamp();
 static unsigned long long readTXTimestamp();

 // Chip Interaction
 static uint32_t write(int base, int sub, uint32_t data, int data_len);
 static uint32_t write(int base, int sub, uint32_t data);

 static uint32_t read(int base, int sub);
 static uint8_t read8bit(int base, int sub);
 static uint32_t readOTP(uint8_t addr);

 // Delayed Sending Settings
 static void writeTXDelay(uint32_t delay);
 static void prepareDelayedTX();

 // Radio Stage Settings / Transfer and Receive Modes
 static void delayedTXThenRX();
 static void delayedTX();
 static void standardTX();
 static void standardRX();
 static void TXInstantRX();

 // DWM3000 Firmware Interaction
 static void softReset();
 static void hardReset();
 static void clearSystemStatus();

 // Hardware Status Information
 static void pullLEDHigh(int led);
 static void pullLEDLow(int led);

 // Calculation and Conversion
 static double convertToCM(int DWM3000_ps_units);
 static void calculateTXRXdiff();

 // Printing
 static void printRoundTripInformation();
 static void printDouble(double val, unsigned int precision, bool linebreak);

private:
 // Single Bit Settings
 static void setBit(int reg_addr, int sub_addr, int shift, bool b);
 static void setBitLow(int reg_addr, int sub_addr, int shift);
 static void setBitHigh(int reg_addr, int sub_addr, int shift);

 // Fast Commands
 static void writeFastCommand(int cmd);

 // SPI Interaction
 static uint32_t readOrWriteFullAddress(uint32_t base, uint32_t sub, uint32_t data, uint32_t data_len, uint32_t readWriteBit);
 static uint32_t sendBytes(int b[], int lenB, int recLen);

 // Soft Reset Helper Method
 static void clearAONConfig();

 // Other Helper Methods
 static unsigned int countBits(unsigned int number);
 static int checkForDevID();
};

extern DWM3000Class DWM3000;

DWM3000Class DWM3000;

// Initial Radio Configuration
int DWM3000Class::config[] = {
   CHANNEL_5,         // Channel
   PREAMBLE_128,      // Preamble Length
   9,                 // Preamble Code (Same for RX and TX!)
   PAC8,              // PAC
   DATARATE_6_8MB,    // Datarate
   PHR_MODE_STANDARD, // PHR Mode
   PHR_RATE_850KB     // PHR Rate
};

/*
#####  Chip Setup  #####
*/

/*
Selects a SPI device through its Chip Select pin
@param cs The pin number of the selected SPI device
*/
void DWM3000Class::spiSelect(uint8_t cs)
{
 pinMode(cs, OUTPUT);
 digitalWrite(cs, HIGH);

 delay(5);
}

/*
Initializes the SPI Interface
*/
void DWM3000Class::begin()
{
 delay(5);
 pinMode(CHIP_SELECT_PIN, OUTPUT);
 SPI.begin();

 delay(5);

 spiSelect(CHIP_SELECT_PIN);

 Serial.println("[INFO] SPI ready");
}

/*
Initializes the chip, checks for a connection and sets up an initial configuration
*/
void DWM3000Class::init()
{
 Serial.println("\n+++ DecaWave DWM3000 Test +++\n");

 if (!checkForDevID())
 {
   Serial.println("[ERROR] Dev ID is wrong! Aborting!");
   return;
 }

 setBitHigh(GEN_CFG_AES_LOW_REG, 0x10, 4);

 while (!checkForIDLE())
 {
   Serial.println("[WARNING] IDLE FAILED (stage 1)");
   delay(100);
 }

 softReset();

 delay(200);

 while (!checkForIDLE())
 {
   Serial.println("[WARNING] IDLE FAILED (stage 2)");
   delay(100);
 }

 uint32_t ldo_low = readOTP(0x04);
 uint32_t ldo_high = readOTP(0x05);
 uint32_t bias_tune = readOTP(0xA);
 bias_tune = (bias_tune >> 16) & BIAS_CTRL_BIAS_MASK;

 if (ldo_low != 0 && ldo_high != 0 && bias_tune != 0)
 {
   write(0x11, 0x1F, bias_tune);

   write(0x0B, 0x08, 0x0100);
 }

 int xtrim_value = readOTP(0x1E);

 xtrim_value = xtrim_value == 0 ? 0x2E : xtrim_value; // if xtrim_value from OTP memory is 0, choose 0x2E as default value

 write(FS_CTRL_REG, 0x14, xtrim_value);
 if (DEBUG_OUTPUT)
   Serial.print("xtrim: ");
 if (DEBUG_OUTPUT)
   Serial.println(xtrim_value);

 writeSysConfig();

 write(0x00, 0x3C, 0xFFFFFFFF); // Set Status Enable
 write(0x00, 0x40, 0xFFFF);

 write(0x0A, 0x00, 0x000900, 3); // AON_DIG_CFG register setup; sets up auto-rx calibration and on-wakeup GO2IDLE  //0xA

 /*
  * Set RX and TX config
  */
 write(0x3, 0x1C, 0x10000240); // DGC_CFG0

 write(0x3, 0x20, 0x1B6DA489); // DGC_CFG1

 write(0x3, 0x38, 0x0001C0FD); // DGC_LUT_0

 write(0x3, 0x3C, 0x0001C43E); // DGC_LUT_1

 write(0x3, 0x40, 0x0001C6BE); // DGC_LUT_2

 write(0x3, 0x44, 0x0001C77E); // DGC_LUT_3

 write(0x3, 0x48, 0x0001CF36); // DGC_LUT_4

 write(0x3, 0x4C, 0x0001CFB5); // DGC_LUT_5

 write(0x3, 0x50, 0x0001CFF5); // DGC_LUT_6

 write(0x3, 0x18, 0xE5E5); // THR_64 value set to 0x32
 int f = read(0x4, 0x20);

 // SET PAC TO 32 (0x00) reg:06:00 bits:1-0, bit 4 to 0 (00001100) (0xC)
 write(0x6, 0x0, 0x81101C);

 write(0x07, 0x34, 0x4); // Enable temp sensor readings
 

 write(0x07, 0x48, 0x14);       // LDO_RLOAD to 0x14 //0x7
 write(0x07, 0x1A, 0x0E);       // RF_TX_CTRL_1 to 0x0E
 write(0x07, 0x1C, 0x1C071134); // RF_TX_CTRL_2 to 0x1C071134 (due to channel 5, else (9) to 0x1C010034)
 write(0x09, 0x00, 0x1F3C);     // PLL_CFG to 0x1F3C (due to channel 5, else (9) to 0x0F3C)  //0x9
 write(0x09, 0x80, 0x81);       // PLL_CAL config to 0x81

 write(0x11, 0x04, 0xB40200);

 write(0x11, 0x08, 0x80030738);
 Serial.println("[INFO] Initialization finished.\n");
}

/*
Writes the initial configuration to the chip
*/
void DWM3000Class::writeSysConfig()
{
 int usr_cfg = (STDRD_SYS_CONFIG & 0xFFF) | (config[5] << 3) | (config[6] << 4);

 write(GEN_CFG_AES_LOW_REG, 0x10, usr_cfg);

 if (config[2] > 24)
 {
   Serial.println("[ERROR] SCP ERROR! TX & RX Preamble Code higher than 24!");
 }

 int otp_write = 0x1400;

 if (config[1] >= 256)
 {
   otp_write |= 0x04;
 }

 write(OTP_IF_REG, 0x08, otp_write); // set OTP config
 write(DRX_REG, 0x00, 0x00, 1);      // reset DTUNE0_CONFIG

 write(DRX_REG, 0x0, config[3]);

 // 64 = STS length
 write(STS_CFG_REG, 0x0, 64 / 8 - 1);

 write(GEN_CFG_AES_LOW_REG, 0x29, 0x00, 1);

 write(DRX_REG, 0x0C, 0xAF5F584C);

 int chan_ctrl_val = read(GEN_CFG_AES_HIGH_REG, 0x14); // Fetch and adjust CHAN_CTRL data
 chan_ctrl_val &= (~0x1FFF);

 chan_ctrl_val |= config[0]; // Write RF_CHAN

 chan_ctrl_val |= 0x1F00 & (config[2] << 8);
 chan_ctrl_val |= 0xF8 & (config[2] << 3);
 chan_ctrl_val |= 0x06 & (0x01 << 1);

 write(GEN_CFG_AES_HIGH_REG, 0x14, chan_ctrl_val); // Write new CHAN_CTRL data with updated values

 int tx_fctrl_val = read(GEN_CFG_AES_LOW_REG, 0x24);

 tx_fctrl_val |= (config[1] << 12); // Add preamble length
 tx_fctrl_val |= (config[4] << 10); // Add data rate

 write(GEN_CFG_AES_LOW_REG, 0x24, tx_fctrl_val);

 write(DRX_REG, 0x02, 0x81);

 int rf_tx_ctrl_2 = 0x1C071134;
 int pll_conf = 0x0F3C;

 if (config[0])
 {
   rf_tx_ctrl_2 &= ~0x00FFFF;
   rf_tx_ctrl_2 |= 0x000001;
   pll_conf &= 0x00FF;
   pll_conf |= 0x001F;
 }

 write(RF_CONF_REG, 0x1C, rf_tx_ctrl_2);
 write(FS_CTRL_REG, 0x00, pll_conf);

 write(RF_CONF_REG, 0x51, 0x14);

 write(RF_CONF_REG, 0x1A, 0x0E);

 write(FS_CTRL_REG, 0x08, 0x81);

 write(GEN_CFG_AES_LOW_REG, 0x44, 0x02);

 write(PMSC_REG, 0x04, 0x300200); // Set clock to auto mode

 write(PMSC_REG, 0x08, 0x0138);

 int success = 0;
 for (int i = 0; i < 100; i++)
 {
   if (read(GEN_CFG_AES_LOW_REG, 0x0) & 0x2)
   {
     success = 1;
     break;
   }
 }

 if (!success)
 {
   Serial.println("[ERROR] Couldn't lock PLL Clock!");
 }
 else
 {
   Serial.println("[INFO] PLL is now locked.");
 }

 int otp_val = read(OTP_IF_REG, 0x08);
 otp_val |= 0x40;
 if (config[0])
   otp_val |= 0x2000;

 write(OTP_IF_REG, 0x08, otp_val);

 write(RX_TUNE_REG, 0x19, 0xF0);

 int ldo_ctrl_val = read(RF_CONF_REG, 0x48); // Save original LDO_CTRL data
 int tmp_ldo = (0x105 | 0x100 | 0x4 | 0x1);

 write(RF_CONF_REG, 0x48, tmp_ldo);

 write(EXT_SYNC_REG, 0x0C, 0x020000); // Calibrate RX

 int l = read(0x04, 0x0C);

 delay(20);

 write(EXT_SYNC_REG, 0x0C, 0x11); // Enable calibration

 int succ = 0;
 for (int i = 0; i < 100; i++)
 {
   if (read(EXT_SYNC_REG, 0x20))
   {
     succ = 1;
     break;
   }
   delay(10);
 }

 if (succ)
 {
   Serial.println("[INFO] PGF calibration complete.");
 }
 else
 {
   Serial.println("[ERROR] PGF calibration failed!");
 }

 write(EXT_SYNC_REG, 0x0C, 0x00);
 write(EXT_SYNC_REG, 0x20, 0x01);

 int rx_cal_res = read(EXT_SYNC_REG, 0x14);
 if (rx_cal_res == 0x1fffffff)
 {
   Serial.println("[ERROR] PGF_CAL failed in stage I!");
 }
 rx_cal_res = read(EXT_SYNC_REG, 0x1C);
 if (rx_cal_res == 0x1fffffff)
 {
   Serial.println("[ERROR] PGF_CAL failed in stage Q!");
 }

 write(RF_CONF_REG, 0x48, ldo_ctrl_val); // Restore original LDO_CTRL data

 write(0x0E, 0x02, 0x01); // Enable full CIA diagnostics to get signal strength information

 setTXAntennaDelay(ANTENNA_DELAY); // set default antenna delay
}

/*
Configures the chip for usage as a Transfer Device
*/
void DWM3000Class::configureAsTX()
{
 write(RF_CONF_REG, 0x1C, 0x34); // write pg_delay
 write(GEN_CFG_AES_HIGH_REG, 0x0C, 0xFDFDFDFD);
}

/*
Sets the first 4 GPIO pins as output for external measurements and LED usage
*/
void DWM3000Class::setupGPIO()
{
 write(0x05, 0x08, 0xF0); // Set GPIO0 - GPIO3 as OUTPUT on DWM3000
}

/*
#####  Double-Sided Ranging  #####
*/

/*
Sends a Frame that is supposed to work in double sided ranging (See DWM3000 User Manual 12.3 for more)
@param stage Double-sided Ranging is more complicated than regular single-sided Ranging. Therefore,
             stages were introduced to make sure that the right frames get received at the right time. stage is a 3 bit int.
*/
void DWM3000Class::ds_sendFrame(int stage)
{
 setMode(1);
 write(0x14, 0x01, sender & 0xFF);
 write(0x14, 0x02, destination & 0xFF);
 write(0x14, 0x03, stage & 0x7);
 setFrameLength(4);

 TXInstantRX(); // Await response

 bool error = true;
 for (int i = 0; i < 50; i++)
 {
   if (sentFrameSucc())
   {
     error = false;
     break;
   }
 };
 if (error)
 {
   Serial.println("[ERROR] Could not send frame successfully!");
 }
}

/*
Send the information that chip B collected to chip A for final time calculations
@param t_roundB The time that it took between chip B (this chip) sending an answer and getting a response (rx2 - tx1)
@param t_replyB The time that the chip took to process the received frame (tx1 - rx1)
*/
void DWM3000Class::ds_sendRTInfo(int t_roundB, int t_replyB)
{
 setMode(1);
 write(0x14, 0x01, destination & 0xFF);
 write(0x14, 0x02, sender & 0xFF);
 write(0x14, 0x03, 4);
 write(0x14, 0x04, t_roundB);
 write(0x14, 0x08, t_replyB);

 setFrameLength(12);

 TXInstantRX();
}

/*
Process all Round Trip Time info
@param t_roundA The time it took between chip A sending a frame and getting a response
@param t_replyA The time that chip A took to process the received frame
@param t_roundB The time that it took between chip B sending an answer and getting a response
@param t_replyB The time that chip B took to process the received frame
@param clk_offset The calculated clock offset between both chips (See DWM3000 User Manual 10.1 for more)
@return returns the time in units of 15.65ps that the frames were in the air on average (only one direction)
*/
int DWM3000Class::ds_processRTInfo(int t_roundA, int t_replyA, int t_roundB, int t_replyB, int clk_offset)
{ // returns ranging time in DWM3000 ps units (~15.65ps per unit)
 if (DEBUG_OUTPUT)
 {
   Serial.println("\nProcessing Information:");
   Serial.print("t_roundA: ");
   Serial.println(t_roundA);
   Serial.print("t_replyA: ");
   Serial.println(t_replyA);
   Serial.print("t_roundB: ");
   Serial.println(t_roundB);
   Serial.print("t_replyB: ");
   Serial.println(t_replyB);
 }

 int reply_diff = t_replyA - t_replyB;

 long double clock_offset = t_replyA > t_replyB ? 1.0 + getClockOffset(clk_offset) : 1.0 - getClockOffset(clk_offset);

 int first_rt = t_roundA - t_replyB;
 int second_rt = t_roundB - t_replyA;

 int combined_rt = (first_rt + second_rt - (reply_diff - (reply_diff * clock_offset))) / 2;
 int combined_rt_raw = (first_rt + second_rt) / 2;

 return combined_rt / 2; // divided by 2 to get just one range
}

/*
Returns the stage that the frame was sent in
@return The stage that the frame was sent in (read from the TX_Buffer)
*/
int DWM3000Class::ds_getStage()
{
 return read(0x12, 0x03) & 0b111;
}

/*
Checks if frame is error frame by checking its mode bits
@return True if mode == 7; False if anything else
*/
bool DWM3000Class::ds_isErrorFrame()
{
 return ((read(0x12, 0x00) & 0x7) == 7);
}

/*
Sends a frame that has its mode set to 7 (Error Frame). Instantly switches to receive mode (RX)
*/
void DWM3000Class::ds_sendErrorFrame()
{
 Serial.println("[WARNING] Error Frame sent. Reverting back to stage 0.");
 setMode(7);
 setFrameLength(3);
 standardTX();
}

/*
#####  Radio Settings  #####
*/

/*
Set the channel that the chip should operate on
@param data CHANNEL_5 or CHANNEL_9
*/
void DWM3000Class::setChannel(uint8_t data)
{
 if (data == CHANNEL_5 || data == CHANNEL_9)
   config[0] = data;
}
 

void DWM3000Class::setPreambleLength(uint8_t data)
{
 if (data == PREAMBLE_32 || data == PREAMBLE_64 || data == PREAMBLE_1024 || data == PREAMBLE_256 || data == PREAMBLE_512 || data == PREAMBLE_1024 || data == PREAMBLE_1536 || data == PREAMBLE_2048 || data == PREAMBLE_4096)
   config[1] = data;
}

/*
Set the preamble code
@param data Should be between 9 and 12
*/
void DWM3000Class::setPreambleCode(uint8_t data)
{
 if (data <= 12 && data >= 9)
   config[2] = data;
}

/*
Set the PAC size
@param data PAC4, PAC8, PAC16 or PAC32
*/
void DWM3000Class::setPACSize(uint8_t data)
{
 if (data == PAC4 || data == PAC8 || data == PAC16 || data == PAC32)
   config[3] = data;
}

/*
Set the datarate the chip sends and receives on
@param data DATARATE_6_8_MB or DATARATE_850KB
*/
void DWM3000Class::setDatarate(uint8_t data)
{
 if (data == DATARATE_6_8MB || data == DATARATE_850KB)
   config[4] = data;
}

/*
Set the PHR mode for the chip
@param data PHR_MODE_STANDARD or PHR_MODE_LONG
*/
void DWM3000Class::setPHRMode(uint8_t data)
{
 if (data == PHR_MODE_STANDARD || data == PHR_MODE_LONG)
   config[5] = data;
}

/*
Set the PHR rate for the chip
@param data PHR_RATE_6_8MB or PHR_RATE_850KB
*/
void DWM3000Class::setPHRRate(uint8_t data)
{
 if (data == PHR_RATE_6_8MB || data == PHR_RATE_850KB)
   config[6] = data;
}

/*
#####  Protocol Settings  #####
*/

/*
Sets the frame type/mode to determine between double-sided and error frames.
@param mode The mode that should be used:
   * 0 - Standard
   * 1 - Double-Sided Ranging
   * 2-6 - Reserved
   * 7 - Error
*/
void DWM3000Class::setMode(int mode)
{
 write(0x14, 0x00, mode & 0x7);
}

/*
Writes the given data to the chips TX Frame buffer
@param frame_data The data that should be written onto the chip
*/
void DWM3000Class::setTXFrame(unsigned long long frame_data)
{ // deprecated! use write(TX_BUFFER_REG, [...]);
 if (frame_data > ((pow(2, 8 * 8) - FCS_LEN)))
 {
   Serial.println("[ERROR] Frame is too long (> 1023 Bytes - FCS_LEN)!");
   return;
 }

 write(TX_BUFFER_REG, 0x00, frame_data);
}

/*
Sets the frames data length in bytes
@param frameLen The length of the data in bytes
*/
void DWM3000Class::setFrameLength(int frameLen)
{ // set Frame length in Bytes
 frameLen = frameLen + FCS_LEN;
 int curr_cfg = read(0x00, 0x24);
 if (frameLen > 1023)
 {
   Serial.println("[ERROR] Frame length + FCS_LEN (2) is longer than 1023. Aborting!");
   return;
 }
 int tmp_cfg = (curr_cfg & 0xFFFFFC00) | frameLen;

 write(GEN_CFG_AES_LOW_REG, 0x24, tmp_cfg);
}

/*
Set the Antenna Delay for delayedTX operations
@param data Can be anything between 0 and 0xFFFF
*/
void DWM3000Class::setTXAntennaDelay(int delay)
{
 ANTENNA_DELAY = delay;
 write(0x01, 0x04, delay);
}

/*
Set the chips sender ID. As long as the value is not changed, it won't be changed by the program.
@param senderID The ID that should be set. Can be between 0 and 255. Default is 0
*/
void DWM3000Class::setSenderID(int senderID)
{
 sender = senderID;
}

/*
Set the destination ID. As long as the value is not changed, it won't be changed by the program. If you want to send a second frame, it will still hold the same destination ID!
@param destID The ID that the frame should be sent to. Can be between 0 and 255. Default is 0
*/
void DWM3000Class::setDestinationID(int destID)
{
 destination = destID;
}

/*
#####  Status Checks  #####
*/

/*
Checks if a frame got received successfully
@return 1 if successfully received; 2 if RX Status Error occurred; 0 if no frame got received
*/
int DWM3000Class::receivedFrameSucc()
{
 int sys_stat = read(GEN_CFG_AES_LOW_REG, 0x44);
 if ((sys_stat & SYS_STATUS_FRAME_RX_SUCC) > 0)
 {
   return 1;
 }
 else if ((sys_stat & SYS_STATUS_RX_ERR) > 0)
 {
   return 2;
 }
 return 0;
}

/*
Checks if a frame got sent successfully
@return 1 if successfully sent; 2 if TX Status Error occured; 0 if no frame got sent
*/
int DWM3000Class::sentFrameSucc()
{ // No frame sent: 0; frame sent: 1; error while sending: 2
 int sys_stat = read(GEN_CFG_AES_LOW_REG, 0x44);
 if ((sys_stat & SYS_STATUS_FRAME_TX_SUCC) == SYS_STATUS_FRAME_TX_SUCC)
 {
   return 1;
 }
 return 0;
}

/*
Returns the senderID of the received frame.
@return senderID of the received frame by reading out the frames data
*/
int DWM3000Class::getSenderID()
{
 return read(0x12, 0x01) & 0xFF;
}

/*
Returns the destinationID of the received frame.
@return destinationID of the received frame by reading out the frames data
*/
int DWM3000Class::getDestinationID()
{
 return read(0x12, 0x02) & 0xFF;
}

/*
Checks if the chip has its Power Management System Control (PMSC) module in IDLE mode
@return True if in IDLE, False if not
*/
bool DWM3000Class::checkForIDLE()
{
 return (read(0x0F, 0x30) >> 16 & PMSC_STATE_IDLE) == PMSC_STATE_IDLE || (read(0x00, 0x44) >> 16 & (SPIRDY_MASK | RCINIT_MASK)) == (SPIRDY_MASK | RCINIT_MASK) ? 1 : 0;
}

/*
Checks if SPI can communicate with the chip
@return 1 if True, 0 if False
*/
bool DWM3000Class::checkSPI()
{
 return checkForDevID();
}

/*
#####  Radio Analytics  #####
*/

/*
Calculates the Signal Strength of the received frame in dBm
NOTE: If not using 64MHz PRF: See user manual chapter 4.7.2 for an alternative calculation method
@return The Signal Strength of the received frame in dBm
*/
double DWM3000Class::getSignalStrength()
{
 int CIRpower = read(0x0C, 0x2C) & 0x1FF;
 int PAC_val = read(0x0C, 0x58) & 0xFFF;
 unsigned int DGC_decision = (read(0x03, 0x60) >> 28) & 0x7;
 double PRF_const = 121.7;

 /*Serial.println("Signal Strength Data:");
   Serial.print("CIR Power: ");
   Serial.println(CIRpower);
   Serial.print("PAC val: ");
   Serial.println(PAC_val);
   Serial.print("DGC decision: ");
   Serial.println(DGC_decision);*/

 return 10 * log10((CIRpower * (1 << 21)) / pow(PAC_val, 2)) + (6 * DGC_decision) - PRF_const;
}

/*
Calculates the First Path Signal Strength of the received frame in dBm. Useful to check if a ranging was NLOS or LOS by comparing it to the overall Signal Strength.
@return The First Path Signal Strength of the received frame in dBm
*/
double DWM3000Class::getFirstPathSignalStrength()
{
 float f1 = (read(0x0C, 0x30) & 0x3FFFFF) >> 2;
 float f2 = (read(0x0C, 0x34) & 0x3FFFFF) >> 2;
 float f3 = (read(0x0C, 0x38) & 0x3FFFFF) >> 2;

 int PAC_val = read(0x0C, 0x58) & 0xFFF;
 unsigned int DGC_decision = (read(0x03, 0x60) >> 28) & 0x7;
 double PRF_const = 121.7;

 return 10 * log10((pow(f1, 2) + pow(f2, 2) + pow(f3, 2)) / pow(PAC_val, 2)) + (6 * DGC_decision) - PRF_const;
}

/*
Get the currently set Antenna Delay for delayedTX operations
.@return Antenna Delay
*/
int DWM3000Class::getTXAntennaDelay()
{ // DEPRECATED use ANTENNA_DELAY variable instead!
 int delay = read(0x01, 0x04) & 0xFFFF;
 return delay;
}

/*
Get the calculated clock offset between this chip and the chip that sent a frame
@return Calculated clock offset of the other chip
*/
long double DWM3000Class::getClockOffset()
{
 if (config[0] == CHANNEL_5)
 {
   return getRawClockOffset() * CLOCK_OFFSET_CHAN_5_CONSTANT / 1000000;
 }
 else
 {
   return getRawClockOffset() * CLOCK_OFFSET_CHAN_9_CONSTANT / 1000000;
 }
}

/*
Get the calculated clock offset from the second chips perspective
@return Calculated clock offset of this chip from the other chips perspective
*/
long double DWM3000Class::getClockOffset(int32_t sec_clock_offset)
{
 if (config[0] == CHANNEL_5)
 {
   return sec_clock_offset * CLOCK_OFFSET_CHAN_5_CONSTANT / 1000000;
 }
 else
 {
   return sec_clock_offset * CLOCK_OFFSET_CHAN_9_CONSTANT / 1000000;
 }
}

/*
Get the raw clockset offset from the register of the chip
@return Raw clock offset
*/
int DWM3000Class::getRawClockOffset()
{
 int raw_offset = read(0x06, 0x29) & 0x1FFFFF;

 if (raw_offset & (1 << 20))
 {
   raw_offset |= ~((1 << 21) - 1);
 }

 if (DEBUG_OUTPUT)
 {
   Serial.print("Raw offset: ");
   Serial.println(raw_offset);
 }
 return raw_offset;
}

/*
Activates the chips internal temperature sensor and read its temperature
@return the chips current temperature in °C
*/
float DWM3000Class::getTempInC()
{
 write(0x07, 0x34, 0x04); // enable temp sensor readings

 write(0x08, 0x00, 0x01); // enable poll

 while (!(read(0x08, 0x04) & 0x01))
 {
 };

 int res = read(0x08, 0x08);
 res = (res & 0xFF00) >> 8;
 int otp_temp = readOTP(0x09) & 0xFF;
 float tmp = (float)((res - otp_temp) * 1.05f) + 22.0f;

 write(0x08, 0x00, 0x00, 1); // Reset poll enable

 return tmp;
}

/*
Reads the internal RX Timestamp. The timestamp is a relative timestamp to the chips internal clock. Units of ~15.65ps. (See DWM3000 User Manual 4.1.7 for more)
@return The RX Timestamp in units of ~15.65ps
*/
unsigned long long DWM3000Class::readRXTimestamp()
{
 uint32_t ts_low = read(0x0C, 0x00);
 unsigned long long ts_high = read(0x0C, 0x04) & 0xFF;

 unsigned long long rx_timestamp = (ts_high << 32) | ts_low;

 return rx_timestamp;
}

/*
Reads the internal TX Timestamp. The timestamp is a relative timestamp to the chips internal clock. Units of ~15.65ps. (See DWM3000 User Manual 3.2 for more)
@return The TX Timestamp in units of ~15.65ps
*/
unsigned long long DWM3000Class::readTXTimestamp()
{
 unsigned long long ts_low = read(0x00, 0x74);
 unsigned long long ts_high = read(0x00, 0x78) & 0xFF;

 unsigned long long tx_timestamp = (ts_high << 32) + ts_low;

 return tx_timestamp;
}

/*
#####  Chip Interaction  #####
*/

/*
Writes to a specific chip register address
@param base The chips base register address
@param sub The chips sub register address
@param data The data that should be written
@param dataLen The length of the data that should be written
@return The result of the write operation (typically 0)
*/
uint32_t DWM3000Class::write(int base, int sub, uint32_t data, int dataLen)
{
 return readOrWriteFullAddress(base, sub, data, dataLen, 1);
}

/*
Writes to a specific chip register address and automatically determines the dataLen parameter
@param base The chips base register address
@param sub The chips sub register address
@param data The data that should be written
@return The result of the write operation (typically 0)
*/
uint32_t DWM3000Class::write(int base, int sub, uint32_t data)
{
 return readOrWriteFullAddress(base, sub, data, 0, 1);
}

/*
Reads from a specific chip register address
@param base The chips base register address
@param sub The chips sub register address
@return The result of the read operation
*/
uint32_t DWM3000Class::read(int base, int sub)
{
 uint32_t tmp;
 tmp = readOrWriteFullAddress(base, sub, 0, 0, 0);
 if (DEBUG_OUTPUT)
   Serial.println("");

 return tmp;
}

/*
Reads just 1 Byte from the chip
@param base The chips base register address
@param sub The chips sub register address
@return The result of the read operation
*/
uint8_t DWM3000Class::read8bit(int base, int sub)
{
 return (uint8_t)(read(base, sub) >> 24);
}

/*
Reads a specific OTP (One Time Programmable) Memory address inside the chips register
@param addr The OTP Memory address
@return The result of the read operation
*/
uint32_t DWM3000Class::readOTP(uint8_t addr)
{
 write(OTP_IF_REG, 0x04, addr);
 write(OTP_IF_REG, 0x08, 0x02);

 return read(OTP_IF_REG, 0x10);
}

/*
#####  Delayed Sending Settings  #####
*/

/*
Sets a delay for a future TX operation
@param delay The delay in units of ~4ns (see DWM3000 User Manual 8.2.2.9 for more info)
*/
void DWM3000Class::writeTXDelay(uint32_t delay)
{
 write(0x00, 0x2C, delay);
}

/*
A delayed TX is typically performed to have a known delay between sender and receiver.
As the chips delayedTX function has a lower timestamp resolution, the frame gets sent
always a little bit earlier than its supposed to be. For example:
Delay: 10ms. Receive Time of Frame: 2010us (2.01ms). It should send at 12.01ms, but will be
sent at 12ms as the last digits get cut off. These last digits can be precalculated and
sent inside the frame to be added to the RX Timestamp of the receiver. In the above case, 0.01ms
The DX_Time resolution is ~4ns, the chips internal clock resolution is ~15.65ps.

This function calculates the missing delay time, adds it to the frames payload and sets the fixed delay (TRANSMIT_DELAY).
*/
void DWM3000Class::prepareDelayedTX()
{
 long long rx_ts = readRXTimestamp();

 uint32_t exact_tx_timestamp = (long long)(rx_ts + TRANSMIT_DELAY) >> 8;

 long long calc_tx_timestamp = ((rx_ts + TRANSMIT_DELAY) & ~TRANSMIT_DIFF) + ANTENNA_DELAY;

 uint32_t reply_delay = calc_tx_timestamp - rx_ts;

 /*
   * PAYLOAD DESIGN:
   +------+-----------------------------------------------------------------------+-------------------------------+-------------------------------+------+------+------+-----+
   | Byte |                                 1 (0x00)                              |           2 (0x01)            |           3 (0x02)            |     4 - 6 (0x03-0x05)    |
   +------+-----+-----+----+----------+----------+----------+----------+----------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+------+------+------+-----+
   | Bits |  1  |  2  |  3 |     4    |     5    |     6    |     7    |     8    | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |                          |
   +------+-----+-----+----+----------+----------+----------+----------+----------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--------------------------+
   |      | Mode bits:     | Reserved | Reserved | Reserved | Reserved | Reserved |           Sender ID           |         Destination ID        | Internal Delay / Payload |
   |      | 0 - Standard   |          |          |          |          |          |                               |                               |                          |
   |      |1-7 - See below |          |          |          |          |          |                               |                               |                          |
   +------+----------------+----------+----------+----------+----------+----------+-------------------------------+-------------------------------+--------------------------+
   *
   * Mode bits:
   * 0 - Standard
   * 1 - Double Sided Ranging
   * 2-6 - Reserved
   * 7 - Error
   */

 write(0x14, 0x01, sender & 0xFF);
 write(0x14, 0x02, destination & 0xFF);
 write(0x14, 0x03, reply_delay); // set frame content

 setFrameLength(7); // Control Byte (1 Byte) + Sender ID (1 Byte) + Dest. ID (1 Byte) + Reply Delay (4 Bytes) = 7 Bytes

 // Write delay to register
 writeTXDelay(exact_tx_timestamp);
}

/*
#####  Radio Stage Settings / Transfer and Receive Modes  #####
*/

/*
Activates delayed message transfer and switches to receive mode after TX is finished
*/
void DWM3000Class::delayedTXThenRX()
{
 writeFastCommand(0x0F);
}

/*
Activates delayed message transfer
*/
void DWM3000Class::delayedTX()
{
 writeFastCommand(0x3);
}

/*
Performs a standard TX command
*/
void DWM3000Class::standardTX()
{
 DWM3000Class::writeFastCommand(0x01);
}

/*
Performs a standard RX command
*/
void DWM3000Class::standardRX()
{
 DWM3000Class::writeFastCommand(0x02);
}

/*
Performs a TX operation and instantly switches to Receiver mode
*/
void DWM3000Class::TXInstantRX()
{
 DWM3000Class::writeFastCommand(0x0C);
}

/*
#####  DWM3000 Firmware Interaction  #####
*/

/*
Soft resets the chip via software
*/
void DWM3000Class::softReset()
{
 clearAONConfig();

 write(PMSC_REG, 0x04, 0x1); // force clock to FAST_RC/4 clock

 write(PMSC_REG, 0x00, 0x00, 2); // init reset

 delay(100);

 write(PMSC_REG, 0x00, 0xFFFF); // return back

 write(PMSC_REG, 0x04, 0x00, 1); // set clock back to Auto mode
}

/*
Resets the Chip by physically pulling the RST_PIN to LOW
*/
void DWM3000Class::hardReset()
{
 pinMode(RST_PIN, OUTPUT);
 digitalWrite(RST_PIN, LOW); // set reset pin active low to hard-reset DWM3000 chip
 delay(10);
 pinMode(RST_PIN, INPUT); // get pin back in floating state
}

/*
Clears all System Status flags
*/
void DWM3000Class::clearSystemStatus()
{
 write(GEN_CFG_AES_LOW_REG, 0x44, 0x3F7FFFFF);
}

/*
#####  Hardware Status Information  #####
*/

/*
Pulls a specific external LED to HIGH (tested on Makerfabs DWM3000 board)
@param led the index of the LED (0 - 2 possible)
*/
void DWM3000Class::pullLEDHigh(int led)
{
 if (led > 2)
   return;
 led_status = led_status | (1 << led);
 write(0x05, 0x0C, led_status);
}

/*
Pulls a specific external LED to LOW (tested on Makerfabs DWM3000 board)
@param led the index of the LED (0 - 2 possible)
*/
void DWM3000Class::pullLEDLow(int led)
{
 if (led > 2)
   return;
 led_status = led_status & ~((int)1 << led); // https://stackoverflow.com/questions/47981/how-to-set-clear-and-toggle-a…
 write(0x05, 0x0C, led_status);
}

/*
#####  Calculation and Conversion  #####
*/

/*
Convert DWM3000 internal picosecond units (~15.65ps per unit) to cm
@param DWM3000_ps_units DWM3000 internal picosecond units. Gets returned from timestamps for example.
@return The distance in cm
*/
double DWM3000Class::convertToCM(int DWM3000_ps_units)
{
 return (double)DWM3000_ps_units * PS_UNIT * SPEED_OF_LIGHT;
}

/*
Calculate the Round Trip Time (RTT) for a ping operation and print out the distance in cm
*/
void DWM3000Class::calculateTXRXdiff()
{
 unsigned long long ping_tx = readTXTimestamp();
 unsigned long long ping_rx = readRXTimestamp();

 long double clk_offset = getClockOffset();
 long double clock_offset = 1.0 + clk_offset;

 /*
      * PAYLOAD DESIGN:
      +------+-----------------------------------------------------------------------+-------------------------------+-------------------------------+------+------+------+-----+
      | Byte |                                 1 (0x00)                              |           2 (0x01)            |           3 (0x02)            |     4 - 6 (0x03-0x...)   |
      +------+-----+-----+----+----------+----------+----------+----------+----------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+------+------+------+-----+
      | Bits |  1  |  2  |  3 |     4    |     5    |     6    |     7    |     8    | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |                          |
      +------+-----+-----+----+----------+----------+----------+----------+----------+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--------------------------+
      |      | Mode bits:     | Reserved | Reserved | Reserved | Reserved | Reserved |           Sender ID           |         Destination ID        | Internal Delay / Payload |
      |      | 0 - Standard   |          |          |          |          |          |                               |                               |                          |
      |      |1-7 - See below |          |          |          |          |          |                               |                               |                          |
      +------+----------------+----------+----------+----------+----------+----------+-------------------------------+-------------------------------+--------------------------+
   *
   * Mode bits:
   * 0 - Standard
   * 1 - Double Sided Ranging
   * 2-6 - Reserved
   * 7 - Error
   */

 long long t_reply = read(RX_BUFFER_0_REG, 0x03);

 /*
  * Calculate round trip time (see DWM3000 User Manual page 248 for more)
  */

 if (t_reply == 0)
 { // t_reply is 0 when the calculation could not be done on the PONG side
   return;
 }

 long long t_round = ping_rx - ping_tx;
 long long t_prop = lround((t_round - lround(t_reply * clock_offset)) / 2);

 long double t_prop_ps = t_prop * PS_UNIT;

 long double t_prop_cm = t_prop_ps * SPEED_OF_LIGHT;
 if (t_prop_cm >= 0)
 {
   printDouble(t_prop_cm, 100, false); // second value sets the decimal places. 100 = 2 decimal places, 1000 = 3, 10000 = 4, ...
   Serial.println("cm");
 }
}

/*
#####  Printing  #####
*/

/*
Debug Output to print the Round Trip Time (RTT) and essential additional information
*/
void DWM3000Class::printRoundTripInformation()
{
 Serial.println("\nRound Trip Information:");
 long long tx_ts = readTXTimestamp();
 long long rx_ts = readRXTimestamp();

 Serial.print("TX Timestamp: ");
 Serial.println(tx_ts);
 Serial.print("RX Timestamp: ");
 Serial.println(rx_ts);
}

/*
Helper function to print Doubles in an Arduino Console. Prints values with a specific number of decimal places.
@param val The value that should be printed
@param precision Precision is 1 followed by the number of zeros for the desired number of decimal places. Example: printDouble (3.14159, 1000); prints 3.141 (three decimal places).
@param linebreak If True, a linebreak will be added after the print (equal to Serial.println()). If not, no linebreak (equal to Serial.print())
*/
void DWM3000Class::printDouble(double val, unsigned int precision, bool linebreak)
{                         // https://forum.arduino.cc/t/printing-a-double-variable/44327/2
 Serial.print(int(val)); // print the integer part
 Serial.print(".");      // print the decimal point
 unsigned int frac;
 if (val >= 0)
 {
   frac = (val - int(val)) * precision;
 }
 else
 {
   frac = (int(val) - val) * precision;
 }
 if (linebreak)
 {
   Serial.println(frac, DEC); // print the fraction with linebreak
 }
 else
 {
   Serial.print(frac, DEC); // print the fraction without linebreak
 }
}

/*
==========  Private Functions  ==========
*/

/*
#####  Single Bit Settings  #####
*/

/*
Set bit in a defined register address
@param reg_addr The registers base address
@param sub_addr The registers sub address
@param shift The bit that should be modified, relative to the base and sub address (0 for bit 0, 1 for bit 1, etc.)
@param b The state that the bit should be set to. True if should be set to 1, False if 0
*/
void DWM3000Class::setBit(int reg_addr, int sub_addr, int shift, bool b)
{
 uint8_t tmpByte = read8bit(reg_addr, sub_addr);
 if (b)
 {
   bitSet(tmpByte, shift);
 }
 else
 {
   bitClear(tmpByte, shift);
 }
 write(reg_addr, sub_addr, tmpByte);
}

/*
Sets bit to High (1) in a defined register
@param reg_addr The registers base address
@param sub_addr The registers sub address
@param shift The bit that should be modified, relative to the base and sub address (0 for bit 0, 1 for bit 1, etc.)
*/
void DWM3000Class::setBitHigh(int reg_addr, int sub_addr, int shift)
{
 setBit(reg_addr, sub_addr, shift, 1);
}

/*
Sets bit to Low (0) in a defined register
@param reg_addr The registers base address
@param sub_addr The registers sub address
@param shift The bit that should be modified, relative to the base and sub address (0 for bit 0, 1 for bit 1, etc.)
*/
void DWM3000Class::setBitLow(int reg_addr, int sub_addr, int shift)
{
 setBit(reg_addr, sub_addr, shift, 0);
}

/*
#####  Fast Commands  #####
*/

/*
Writes a Fast Command to the chip (See DWM3000 User Manual chapter 9 for more)
@param cmd The command that should be sent
*/
void DWM3000Class::writeFastCommand(int cmd)
{
 if (DEBUG_OUTPUT)
   Serial.print("[INFO] Executing short command: ");

 int header = 0;

 header = header | 0x1;
 header = header | (cmd & 0x1F) << 1;
 header = header | 0x80;

 if (DEBUG_OUTPUT)
   Serial.println(header, BIN);

 int header_arr[] = {header};

 sendBytes(header_arr, 1, 0);
}

/*
#####  SPI Interaction  #####
*/

/*
Helper function to read or write to a specific chip register address
@param base The base register address
@param sub  The sub register address
@param data The data that should be written (if anything should be written, else left at 0)
@param dataLen The length of the data that should be sent in bits. Can be left at zero to automatically determine the data length,
       but can be very useful if e.g. 32 bits of 0x00 should be written
@param readWriteBit Defines if a read or write operation will be performed. 0 if data should be read back, 1 if only a write should be performed.
@return Returns 0 or the result of the read operation
*/
uint32_t DWM3000Class::readOrWriteFullAddress(uint32_t base, uint32_t sub, uint32_t data, uint32_t dataLen, uint32_t readWriteBit)
{
 uint32_t header = 0x00;

 if (readWriteBit)
   header = header | 0x80;

 header = header | ((base & 0x1F) << 1);

 if (sub > 0)
 {
   header = header | 0x40;
   header = header << 8;
   header = header | ((sub & 0x7F) << 2);
 }

 uint32_t header_size = header > 0xFF ? 2 : 1;
 uint32_t res = 0;

 if (!readWriteBit)
 {
   int headerArr[header_size];

   if (header_size == 1)
   {
     headerArr[0] = header;
   }
   else
   {
     headerArr[0] = (header & 0xFF00) >> 8;
     headerArr[1] = header & 0xFF;
   }

   res = (uint32_t)sendBytes(headerArr, header_size, 4);
   return res;
 }
 else
 {
   uint32_t payload_bytes = 0;
   if (dataLen == 0)
   {
     if (data > 0)
     {
       uint32_t payload_bits = countBits(data);
       payload_bytes = (payload_bits - (payload_bits % 8)) / 8; // calc the used bytes for transaction
       if ((payload_bits % 8) > 0)
       {
         payload_bytes++;
       }
     }
     else
     {
       payload_bytes = 1;
     }
   }
   else
   {
     payload_bytes = dataLen;
   }
   int payload[header_size + payload_bytes];

   if (header_size == 1)
   {
     payload[0] = header;
   }
   else
   {
     payload[0] = (header & 0xFF00) >> 8;
     payload[1] = header & 0xFF;
   }

   for (int i = 0; i < payload_bytes; i++)
   {
     payload[header_size + i] = (data >> i * 8) & 0xFF;
   }

   res = (uint32_t)sendBytes(payload, 2 + payload_bytes, 0); // "2 +" because the first 2 bytes are the header part
   return res;
 }
}

/*
Internal helper function to send and receive Bytes through the SPI Interface
@param b The bytes to be sent as an array
@param lenB The length of the array b
@param recLen The length of bytes that should be received back after sending the data b
@return Returns 0 or the received bytes from the chip
*/
uint32_t DWM3000Class::sendBytes(int b[], int lenB, int recLen)
{
 digitalWrite(CHIP_SELECT_PIN, LOW);
 for (int i = 0; i < lenB; i++)
 {
   SPI.transfer(b[i]);
 }
 int rec;
 uint32_t val, tmp;
 if (recLen > 0)
 {
   for (int i = 0; i < recLen; i++)
   {
     tmp = SPI.transfer(0x00);
     if (i == 0)
     {
       val = tmp; // Read first 4 octets
     }
     else
     {
       val |= (uint32_t)tmp << 8 * i;
     }
   }
 }
 else
 {
   val = 0;
 }
 digitalWrite(CHIP_SELECT_PIN, HIGH);
 return val;
}

/*
#####  Soft Reset Helper Method  #####
*/

/*
Clears the Always On register. This register stores information as long as power is supplied to the chip.
*/
void DWM3000Class::clearAONConfig()
{
 write(AON_REG, NO_OFFSET, 0x00, 2);
 write(AON_REG, 0x14, 0x00, 1);

 write(AON_REG, 0x04, 0x00, 1); // clear control of aon reg

 write(AON_REG, 0x04, 0x02);

 delay(1);
}

/*
#####  Other Helper Methods  #####
*/

/*
Helper function to count the bits of a number
return length of a number in bits
*/
unsigned int DWM3000Class::countBits(unsigned int number)
{
 return (int)log2(number) + 1;
}

/*
Checks if a DeviceID can be read from the device (if not, SPI can not connect to the chip). Acts as a sanity check.
@return 1 if DeviceID could be read; 0 if not.
*/
int DWM3000Class::checkForDevID()
{
 int res = read(GEN_CFG_AES_LOW_REG, NO_OFFSET);
 if (res != 0xDECA0302 && res != 0xDECA0312)
 {
   Serial.println("[ERROR] DEV_ID IS WRONG!");
   return 0;
 }
 return 1;
}

void resetRadio()
{
 Serial.println("[INFO] Performing radio reset...");
 DWM3000.softReset();
 delay(100);
 DWM3000.clearSystemStatus();
 DWM3000.configureAsTX();
 DWM3000.standardRX();
}

void setup()
{
 Serial.begin(115200);
 DWM3000.begin();
 DWM3000.hardReset();
 delay(200);

 if (!DWM3000.checkSPI())
 {
   Serial.println("[ERROR] Could not establish SPI Connection to DWM3000!");
   while (1)
     ;
 }

 while (!DWM3000.checkForIDLE())
 {
   Serial.println("[ERROR] IDLE1 FAILED\r");
   delay(1000);
 }

 DWM3000.softReset();
 delay(200);

 if (!DWM3000.checkForIDLE())
 {
   Serial.println("[ERROR] IDLE2 FAILED\r");
   while (1)
     ;
 }

 DWM3000.init();
 DWM3000.setupGPIO();

 // Set antenna delay - calibrate this for your hardware!
 DWM3000.setTXAntennaDelay(16350);

 // Set anchor ID
 DWM3000.setSenderID(ANCHOR_ID);

 Serial.print("> ANCHOR ");
 Serial.print(ANCHOR_ID);
 Serial.println(" - Ready for ranging <");
 Serial.print("Antenna delay set to: ");
 Serial.println(DWM3000.getTXAntennaDelay());
 Serial.println("[INFO] Setup finished.");

 DWM3000.configureAsTX();
 DWM3000.clearSystemStatus();
 DWM3000.standardRX();
}

void loop()
{
 if (DWM3000.receivedFrameSucc() == 1 && DWM3000.ds_getStage() == 1 && DWM3000.getDestinationID() == ANCHOR_ID)
 {
   // Reset session if new ranging request arrives
   if (curr_stage != 0)
   {
     Serial.println("[INFO] New request - resetting session");
     curr_stage = 0;
     t_roundB = 0;
     t_replyB = 0;
   }
 }
 switch (curr_stage)
 {
 case 0: // Await ranging
   t_roundB = 0;
   t_replyB = 0;
   last_ranging_time = millis(); // Reset timeout timer

   if (rx_status = DWM3000.receivedFrameSucc())
   {
     DWM3000.clearSystemStatus();
     if (rx_status == 1)
     { // If frame reception was successful
       // Only respond if frame is addressed to us
       if (DWM3000.getDestinationID() == ANCHOR_ID)
       {
         if (DWM3000.ds_isErrorFrame())
         {
           Serial.println("[WARNING] Received error frame!");
           curr_stage = 0;
           DWM3000.standardRX();
         }
         else if (DWM3000.ds_getStage() != 1)
         {
           Serial.print("[WARNING] Unexpected stage: ");
           Serial.println(DWM3000.ds_getStage());
           DWM3000.ds_sendErrorFrame();
           DWM3000.standardRX();
           curr_stage = 0;
         }
         else
         {
           curr_stage = 1;
         }
       }
       else
       {
         // Not for us, go back to RX
         DWM3000.standardRX();
       }
     }
     else
     {
       Serial.println("[ERROR] Receiver Error occurred!");
       DWM3000.clearSystemStatus();
     }
   }
   else if (millis() - last_ranging_time > RESPONSE_TIMEOUT_MS)
   {
     Serial.println("[WARNING] Timeout waiting for ranging request");
     if (++retry_count > MAX_RETRIES)
     {
       Serial.println("[ERROR] Max retries reached, resetting radio");
       resetRadio();
       retry_count = 0;
     }
     DWM3000.standardRX(); // Reset to listening mode
   }
   break;

 case 1: // Ranging received. Sending response
   DWM3000.ds_sendFrame(2);

   rx = DWM3000.readRXTimestamp();
   tx = DWM3000.readTXTimestamp();

   t_replyB = tx - rx;
   curr_stage = 2;
   last_ranging_time = millis(); // Reset timeout timer
   break;

 case 2: // Awaiting response
   if (rx_status = DWM3000.receivedFrameSucc())
   {
     retry_count = 0; // Reset on successful response
     DWM3000.clearSystemStatus();
     if (rx_status == 1)
     { // If frame reception was successful
       if (DWM3000.ds_isErrorFrame())
       {
         Serial.println("[WARNING] Received error frame!");
         curr_stage = 0;
         DWM3000.standardRX();
       }
       else if (DWM3000.ds_getStage() != 3)
       {
         Serial.print("[WARNING] Unexpected stage: ");
         Serial.println(DWM3000.ds_getStage());
         DWM3000.ds_sendErrorFrame();
         DWM3000.standardRX();
         curr_stage = 0;
       }
       else
       {
         curr_stage = 3;
       }
     }
     else
     {
       Serial.println("[ERROR] Receiver Error occurred!");
       DWM3000.clearSystemStatus();
     }
   }
   else if (millis() - last_ranging_time > RESPONSE_TIMEOUT_MS)
   {
     Serial.println("[WARNING] Timeout waiting for second response");
     if (++retry_count > MAX_RETRIES)
     {
       Serial.println("[ERROR] Max retries reached, resetting radio");
       resetRadio();
       retry_count = 0;
     }
     curr_stage = 0;
     DWM3000.standardRX();
   }
   break;

 case 3: // Second response received. Sending information frame
   rx = DWM3000.readRXTimestamp();
   t_roundB = rx - tx;
   DWM3000.ds_sendRTInfo(t_roundB, t_replyB);

   curr_stage = 0;
   DWM3000.standardRX();
   break;

 default:
   Serial.print("[ERROR] Entered unknown stage (");
   Serial.print(curr_stage);
   Serial.println("). Reverting back to stage 0");

   curr_stage = 0;
   DWM3000.standardRX();
   break;
 }
}
 

Python Script:
import socket
import threading
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import matplotlib.image as mpimg
import numpy as np
from scipy.optimize import least_squares
import json

# ---------------- CONFIGURATION ---------------- #
HOST = "192.xxx.xx.xx"  # Your PC's IP address
PORT = 7007  # Must match ESP32 port
ANCHOR_POSITIONS = np.array(
  [[15, 5], [290, 5], [165, 625]]  # Anchor 1  # Anchor 2  # Anchor 3
)
MARGIN = 20  # For dynamic zoom (not needed for fixed view)
ROOM_WIDTH = 480  # cm
ROOM_HEIGHT = 650  # cm
IMAGE_FILE = "floorplan.png"  # Background image of your room
# ------------------------------------------------ #

# Global variables
latest_data = None
latest_signal_strengths = None  # New variable for signal strengths
data_lock = threading.Lock()
server_running = True
buffer = ""
 

def trilaterate(distances, anchor_positions):
  """Calculate tag position using trilateration with 3 anchors."""

  def equations(p):
      x, y = p
      return [
          np.sqrt(
              (x - anchor_positions[0][0]) ** 2 + (y - anchor_positions[0][1]) ** 2
          )
          - distances[0],
          np.sqrt(
              (x - anchor_positions[1][0]) ** 2 + (y - anchor_positions[1][1]) ** 2
          )
          - distances[1],
          np.sqrt(
              (x - anchor_positions[2][0]) ** 2 + (y - anchor_positions[2][1]) ** 2
          )
          - distances[2],
      ]

  initial_guess = np.mean(anchor_positions, axis=0)

  try:
      result = least_squares(equations, initial_guess, method="lm")
      return result.x if result.success else None
  except Exception as e:
      print(f"Trilateration error: {e}")
      return None
 

def wifi_server():
  """TCP server to receive data from ESP32"""
  global latest_data, latest_signal_strengths, server_running, buffer

  with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
      s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
      s.bind((HOST, PORT))
      s.listen()
      print(f"Server listening on {HOST}:{PORT}")

      while server_running:
          try:
              conn, addr = s.accept()
              with conn:
                  print(f"Connected by {addr}")
                  while server_running:
                      try:
                          data = conn.recv(1024)
                          if not data:
                              break
                          decoded = data.decode("utf-8")
                          buffer += decoded

                          while "\n" in buffer:
                              line, buffer = buffer.split("\n", 1)
                              line = line.strip()
                              if line:
                                  try:
                                      # Parse JSON data
                                      json_data = json.loads(line)
                                      anchors = json_data["anchors"]  # Extract the anchors dictionary
                                      d1 = float(anchors["A1"]["distance"])
                                      d2 = float(anchors["A2"]["distance"])
                                      d3 = float(anchors["A3"]["distance"])
                                      s1 = float(anchors["A1"]["rssi"])
                                      s2 = float(anchors["A2"]["rssi"])
                                      s3 = float(anchors["A3"]["rssi"])
                                      with data_lock:
                                          latest_data = (d1, d2, d3)
                                          latest_signal_strengths = (s1, s2, s3)

                                      print(f"Tag ID: {json_data['tag_id']}")
                                      print(f"Received data: d1={d1:.2f} cm, d2={d2:.2f} cm, d3={d3:.2f} cm")
                                      print(f"Signal strengths: s1={s1:.2f} dBm, s2={s2:.2f} dBm, s3={s3:.2f} dBm")

                                  except (
                                          ValueError,
                                          KeyError,
                                          json.JSONDecodeError,
                                  ) as e:
                                      print(f"Invalid data: {line} - Error: {e}")
                      except ConnectionResetError:
                          print("Client disconnected")
                          break
          except OSError as e:
              if server_running:
                  print(f"Server error: {e}")
              break
 

# ---------------- PLOTTING SETUP ---------------- #
fig, ax = plt.subplots(figsize=(10, 8))

# Load and display room background image
bg_img = mpimg.imread(IMAGE_FILE)
img_extent = [0, ROOM_WIDTH, 0, ROOM_HEIGHT]
ax.imshow(bg_img, extent=img_extent, origin="lower", alpha=0.6, zorder=-1)

# Plot anchors and create text annotations for signal strength
anchor_texts = []
for i, (x, y) in enumerate(ANCHOR_POSITIONS):
  color = ["g", "b", "m"][i]
  ax.plot(x, y, f"{color}^", markersize=12, label=f"Anchor {i + 1}")
  # Create text object for signal strength, positioned above each anchor
  txt = ax.text(x, y + 20, "", color=color, ha="center", va="bottom")
  anchor_texts.append(txt)

# Tag and path
(tag_dot,) = ax.plot([], [], "ro", markersize=10, label="Tag Position")
(path_line,) = ax.plot([], [], "b-", alpha=0.5, linewidth=1, label="Tag Path")

path_x, path_y = [], []

# Set fixed room size view
ax.set_xlim(0, ROOM_WIDTH)
ax.set_ylim(0, ROOM_HEIGHT)
ax.set_aspect("equal")
ax.grid(True, linestyle="--", alpha=0.7)
ax.legend(loc="upper right")
ax.set_title("Real-time UWB Tag Position Tracking (3 Anchors)", pad=40)
ax.set_xlabel("X Position (cm)", labelpad=10)
ax.set_ylabel("Y Position (cm)", labelpad=10)
 

# ---------------- ANIMATION FUNCTION ---------------- #
def update(frame):
  global latest_data, latest_signal_strengths, path_x, path_y

  with data_lock:
      if latest_data and latest_signal_strengths:
          d1, d2, d3 = latest_data
          s1, s2, s3 = latest_signal_strengths

          # Update signal strength texts
          for i, (txt, sig) in enumerate(zip(anchor_texts, (s1, s2, s3))):
              txt.set_text(f"{sig:.1f} dBm")

          pos = trilaterate([d1, d2, d3], ANCHOR_POSITIONS)
          if pos is not None:
              x_cm, y_cm = pos
              print(f"Tag position: x={x_cm:.1f} cm, y={y_cm:.1f} cm")

              tag_dot.set_data([x_cm], [y_cm])
              path_x.append(x_cm)
              path_y.append(y_cm)
              if len(path_x) > 100:
                  path_x.pop(0)
                  path_y.pop(0)
              path_line.set_data(path_x, path_y)

  return tag_dot, path_line, *anchor_texts
 

# ---------------- MAIN EXECUTION ---------------- #
if __name__ == "__main__":
  server_thread = threading.Thread(target=wifi_server, daemon=True)
  server_thread.start()

  ani = animation.FuncAnimation(
      fig, update, interval=100, cache_frame_data=False, blit=False
  )

  try:
      plt.tight_layout()
      plt.show()
  except KeyboardInterrupt:
      print("\nShutting down server...")
  finally:
      server_running = False
      plt.close()