PolarFire® Core FPGAs and SoC FPGAs
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What It Takes to Make a Chip: India's Semiconductor Scene through InCore's Lens
“Everything starts with the product definition,” is how G. S. Madhusudan, CEO and Co-Founder of InCore Semiconductors, began walking us through the complex web of players that bring a chip to life. Given that we were on a Google Meet, he picked an IP camera chip as his example, because it essentially functions the same way. The list of things this chip does includes
How to Add a Loudspeaker to LiteWing ESP32 Drone for Wireless Audio Announcement
In this project, we upgraded LiteWing, an ESP32-based development drone by adding a lightweight Bluetooth speaker system to extend its capabilities beyond flight. By adding a simple Bluetooth audio setup, the drone can now deliver real-time announcements, voice messages, or music directly from the air without requiring any additional coding. The entire system works through a standard Bluetooth connection, making it easy to set up, practical for demonstrations, events, and experimental applications while also being fun.
If you want to learn how to make a DIY Bluetooth speaker, check out the article titled “Build a Compact and Portable DIY Bluetooth Speaker.” By combining wireless communication and lightweight audio hardware, this setup makes it possible to use the drone announcements, campus activities, safety alerts, and creative applications. Our collection of DIY drone projects focuses on building programmable and sensor-equipped drones using microcontrollers such as ESP32 and related technologies.
Drone with Loudspeaker: Add a Bluetooth Speaker System to the LiteWing ESP32 Drone
A beginner-friendly, step-by-step guide to build a loudspeaker drone for real-time aerial announcements, voice alerts, and Bluetooth audio streaming powered by the LiteWing ESP32 platform.
- Pair the JDY-62 Bluetooth module as a Bluetooth audio receiver.
- Feed the audio signal into the PAM8403 amplifier.
- Drive the 2W 8Ω speaker for audible aerial playback.
- Power everything via a 3.7V–5V boost converter from the drone's VBUS pin.
- Pair your smartphone → stream audio → fly and announce. No code needed.
LiteWing ESP32 Drone Bluetooth Speaker Explanation and Demo Video
Overview of Drones with added Loudspeaker Systems
The drone is an unmanned aerial vehicle integrated with a loudspeaker system, allowing it to transmit live voice announcements, music, and various audio alerts during flight operations.
A drone that has an integrated wireless sound system has all of these components built right into the frame of the craft itself, providing a mobile public address system from any location within the drone’s flight range. This technology can easily be used in areas where traditional ground-level sound systems may not be able to reach their intended audience effectively.
Components Required for the Bluetooth Speaker Drone
To add a drone speaker system to the LiteWing drone, a few basic hardware components are needed. These parts help in receiving wireless audio, amplifying the sound, and supplying proper power to the system. The list below shows all the components used in this project and their purpose.
| Component | Function |
| LiteWing Drone | Receives wireless audio data via Bluetooth from a mobile device |
| PAM8403 Audio Amplifier | Amplifies low-power audio signals to drive the external speaker |
| 2-Watt 8Ω Speaker | Outputs audio for real-time announcements and voice playback |
| 3.7V to 5V Boost Converter | Steps up battery voltage to provide stable power supply for the audio system components |
| Wires | Used to connect the Bluetooth module, amplifier, boost converter, and speaker together |
Hardware Setup and Wiring Guide
The hardware setup involves connecting the drone with a Bluetooth speaker, audio amplifier, speaker, and boost converter to the LiteWing drone. Proper wiring and power connections are important to ensure stable audio output and safe operation during flight. In this section, we will explain how each component is connected and how the overall system is assembled, as shown in the image below.
The image shows the hardware connections for integrating a BLE speaker system with the LiteWing drone.
Key Wiring Points at a Glance
- The JDY-62 Bluetooth module connects to the PAM8403 amplifier, which then drives the 2W speaker. In this connection, the red and black wires are used for the power supply, while the yellow wire carries the audio signal and is connected to the right audio input of the amplifier.
- A 3.7V to 5V boost converter powers the amplifier and speaker to ensure a stable voltage.
- All components are connected to the LiteWing ESP32 drone through the GND and VBUS pins for power.
This setup allows the drone to receive audio via Bluetooth and play it through the speaker while flying.
How the LiteWing Bluetooth Speaker Drone System Works
The LiteWing drone with Bluetooth speaker system works by combining wireless communication, audio processing, and flight control to create an interactive aerial platform. Here’s how it functions step by step:
Wireless Audio Reception
The JDY-62 Bluetooth module acts as the audio receiver. When paired with a mobile device, it receives audio signals wirelessly using Bluetooth. This allows you to stream drone announcements, music, or voice messages directly to the drone while it is flying.
Audio Amplification
The low-power audio signal received from the JDY-62 module is not strong enough to drive a speaker directly. The PAM8403 audio amplifier boosts this signal, ensuring that the output sound is loud and clear for real-time announcements.
Power Supply Management
The drone’s battery voltage (typically 3.7V) is stepped up to a stable 5V using the boost converter. The VIN+ of the boost converter is connected to the VBUS of the drone, ensuring that both the Bluetooth module and the amplifier receive consistent power for uninterrupted operation, even while the drone is flying.
Audio Output
The amplified signal is sent to the 2-Watt 8Ω speaker mounted on the drone. The speaker plays the received audio clearly, allowing the drone to deliver announcements, alerts, or interactive messages from the air. In real-world testing, the drone speaker is clearly audible at typical low-altitude flight heights, making this an effective solution for short-range aerial drone announcement applications such as event broadcasts and safety alerts.
Integration with the Drone
The entire audio system is lightweight and carefully integrated with the LiteWing drone with a loudspeaker. Wires connect the Bluetooth module, amplifier, and speaker, while the ESP32 flight controller continues to manage drone navigation. This ensures that the drone can fly normally while also functioning as a flying audio communication platform.
Working Demonstration
In the working video, you can see the LiteWing drone flying while playing audio in real time through the Bluetooth speaker system. It clearly shows how the drone connects to a mobile phone via Bluetooth and broadcasts voice messages from the air. This video gives a practical view of the setup in action and helps you understand how the system performs.
In our article DIY Gesture Control Drone using Python with LiteWing and ESP32, we built a gesture-controlled system ourselves using an ESP32 and MPU6050 sensor to wirelessly control a LiteWing drone via Bluetooth and Python, and you can try it yourself if you're passionate about innovative DIY tech projects.
Real-World Applications of a Loudspeaker Drone
The ability to broadcast audio from the air makes a loudspeaker drone uniquely versatile across a wide range of industries and use cases. Here are the primary applications of this drone announcement platform:
- Event announcements and public messaging
- Safety alerts and emergency notifications
- Tour guidance and interactive experiences
- Advertising and promotional campaigns
- Search and rescue communication
- Educational demonstrations
- Creative content and entertainment
Troubleshooting Drone Restarting Issue
Connect the VIN+ of the boost converter to the drone’s VBUS pin instead of the 3.3V pin to prevent restarting problems. This is necessary because the 3.3V power line cannot supply enough current for the boost converter and audio components, which causes the drone to reboot. The VBUS pin provides a more stable and higher current power supply, allowing the system to operate smoothly.
| Symptom | Likely Cause | Solution |
| Drone resets on power-up | Insufficient current from 3.3V pin | Move boost converter VIN+ to VBUS pin |
| No audio output | JDY-62 not paired / wrong audio channel | Re-pair device; confirm yellow wire is on R+ input of PAM8403 |
| Drone unstable or drifting | Added weight unbalanced on frame | Redistribute speaker and module mass symmetrically; keep total added weight under 25 g |
Frequently Asked Questions: Drone with Loudspeaker
⇥ 1. How much weight can the LiteWing drone lift?
The LiteWing drone can typically lift around 20 to 30 grams of additional payload, depending on battery and motor performance. For stable flight, it is recommended to keep the added weight as low as possible.
⇥ 2. Is a boost converter mandatory for this setup?
Yes, a boost converter is recommended because the drone battery provides around 3.7V, while the Bluetooth module and amplifier require a stable 5V supply for reliable operation.
⇥ 3. Can I use a different Bluetooth module instead of JDY-62?
Yes, you can use other Bluetooth audio receiver modules, but make sure they support audio output, work on low power, and are lightweight to avoid affecting the drone’s flight performance.
⇥ 4. Do I need to write any code to use the Bluetooth speaker system
No, coding is not required. The system works directly through Bluetooth pairing, allowing audio to be streamed from a mobile device without any programming.
⇥ 5. What precautions should be taken while adding extra hardware?
Keep the added components lightweight, use proper soldering to make strong and reliable connections, ensure a stable power supply, and avoid blocking the propellers or airflow to maintain safe and stable flight.
⇥ 6. What Module Is The Best For A Drone Speaker?
The excellent Bluetooth audio modules available make them ideal choices for drone speakers, as they typically offer wireless audio streaming, very low power draw (3.3 to 5V) and very lightweight (important for maintaining flight performance). All Bluetooth audio modules provide standard analogue audio outputs, allow for Bluetooth pairing, and draw less than 100mA in their operating mode, so any one of these will work with your Bluetooth speaker build.
⇥ 7. What Amplifier Should Be Used For A Drone Speaker?
The PAM8403 Class D stereo amplifier would be the best option to power a drone speaker. It will operate on 5V power, has excellent power efficiency (Class D), has a weight of only a few grams, and provides 3W per channel (more than enough to power a two watt 8Ω speaker at outdoor listening levels). It also has a low idle current; therefore, this will help reduce the overall impact of the amplifier on a drone's flight time.
Related Tutorial: Similar to LiteWing ESP32 Drone
This series shows how to set up the LiteWing ESP32 DIY drone with Betaflight, control it using Python, and enable height hold for stable hovering, perfect for beginners and makers.
How to Connect the LiteWing ESP32 Drone to Betaflight
This project shows how to connect and configure the LiteWing ESP32 drone with Betaflight firmware. By flashing Betaflight on the ESP32 and setting up motors, IMU, receiver, and flight modes, you can convert a small DIY drone into a fully tunable FPV-style flight controller for stable and customizable flight performance.
How to Program the LiteWing Drone using Python with Crazyflie Cflib Python SDK
This guide shows how to program the LiteWing ESP32 DIY Drone Kit for Makers and Developers Q20 C2 using Python with the Crazyflie cflib SDK over Wi-Fi. It explains how to install the Python SDK, connect to the drone via UDP, and write a simple script to arm the drone and spin the motors using Python commands.
How to Use Height Hold Mode in LiteWing ESP32 Drone?
This guide explains how to add and use height hold mode on the LiteWing ESP32 drone using a VL53L1X Time-of-Flight (ToF) distance sensor. It shows how attaching the sensor and activating height hold lets the drone automatically maintain a set altitude for stable hovering and easier flight control.
Reverse Polarity Protection Circuit Using P-Channel MOSFET
You’ve just finished assembling an electronic project and are ready to power it up, only to realize the battery might be connected backwards. In an instant, a simple mistake can destroy hours of work. Reverse polarity is one of the most common causes of circuit failure, from hobby projects to industrial systems. The good news is that a well-designed reverse polarity protection using MOSFET technique can guard every circuit you build, with near-zero efficiency penalty.
A common way to protect a circuit from incorrect power connections is to use a diode, but it wastes energy and generates heat even when connected correctly. This can be a problem for low-voltage devices like battery-powered gadgets. A smarter solution is reverse polarity protection using a MOSFET, which acts as a small electronic switch that only lets power flow the right way, wastes very little energy, and helps the battery last longer. If you want to learn more about MOSFETs, how they’re constructed, their types, and how they work, check out this article: “What is MOSFET: Its Construction, Types and Working.”
Want to learn more about Electronic Circuits and practical project designs? Visit our page for easy tutorials and real-world applications. Start building smarter and safer electronics today!. A smarter solution is reverse polarity protection using a P-channel MOSFET, which acts as an electronically-controlled switch that conducts only under correct polarity, introduces a voltage drop of less than 0.1 V, and helps the battery last longer.
What you will learn: How to design a reverse polarity protection circuit using a MOSFET, why a P-channel MOSFET outperforms a series diode, how to add Zener gate protection for high-voltage environments, and how to select the right MOSFET for your supply voltage.
Table of Contents
- Understanding Reverse Polarity and Why Protection Matters
- Components Required
- Traditional Diode-Based Reverse Polarity Protection
- └ Efficiency Calculation
- Reverse Polarity Protection Circuit Using MOSFET (P-Channel)
- └ Step-by-Step Circuit Assembly
- How it Works
- Comparison
- Working Demonstration
- Enhanced P-MOSFET Reverse Polarity Protection with Zener Gate Clamping
- └ How the Zener Diode Protects the Gate
- How to Choose the Right MOSFET
- Real-World Applications
Understanding Reverse Polarity and Why Protection Matters
Reverse polarity occurs when the positive and negative terminals of a power supply are connected incorrectly to a circuit. This can happen due to:
- Incorrect battery installation
- Miswired connectors
- Accidental connection of the wrong polarity power adapters
- Human error during prototyping or field installation
Without protection, reverse polarity can cause immediate component failure, permanent damage to ICs, or even thermal runaway leading to fire hazards.
Components Required for Reverse Polarity Protection Circuit Using MOSFET
The following components are needed to build the MOSFET-based reverse polarity protection circuit.
| Components Name | Qty | Purpose |
| P-Channel MOSFET (IRF9710) | 1 | Main switching element for reverse polarity protection |
| Diode (IN4007) | 1 | Blocks current when power is connected in reverse. |
| Gate Resistor (1k ohms) | 1 | Limits gate current and stabilizes MOSFET switching |
| DC Power Supply / Battery | 1 | Provides input power to the circuit |
| Load (LED / Microcontroller / Motor) | 1 | Used to test circuit operation |
| Breadboard | 1 | Used for circuit assembly |
| Connecting Wires | As required | Used for making electrical connections |
Traditional Diode-Based Reverse Polarity Protection
The simplest method of reverse polarity protection uses a diode connected in series with the positive supply line. When the power supply is connected with the correct polarity, the diode becomes forward-biased and allows current to flow, with a typical forward voltage drop of around 0.7V. When the supply is connected in reverse polarity, the diode becomes reverse-biased and blocks the current flow, preventing current from reaching the circuit and protecting the connected components from damage.
Although this method provides basic protection, it is not energy efficient. The forward voltage drop across the diode results in continuous power dissipation and reduced available voltage at the load.
Diode Method — Efficiency Calculation
For a 12V system operating at 500mA load current:
Power Loss = 0.7V × 0.5A = 0.35W
Efficiency Impact = (0.7 / 12) × 100% = 5.8% voltage lossThis power loss is converted into heat, which can affect thermal performance and battery life in portable systems.
Because diode-based protection wastes power and produces heat, a reverse polarity protection circuit using MOSFET is a better choice. It offers much lower voltage drop, higher efficiency, and improved overall power performance, making it ideal for battery-powered and high-current applications.
Reverse Polarity Protection Circuit Using MOSFET (P-Channel)
A P-channel MOSFET connected in series with the positive power line, with its gate connected to ground through a pull-down resistor, provides efficient reverse polarity protection with very low voltage loss. When the power supply is connected correctly, the gate to source voltage becomes negative, which turns the MOSFET ON and allows current to flow with very low resistance. When the supply polarity is reversed, the gate to source voltage becomes positive, keeping the MOSFET OFF and blocking the current flow. The internal body diode is oriented to prevent current flow during reverse connection, providing additional protection and ensuring reliable circuit operation.
Step-by-Step Circuit Assembly
- Place the IRF9710 P-Channel MOSFET on the breadboard and find, using the datasheet pin-out, where the Source (S), Gate (G) and Drain (D) are located.
- At the same time, connect a resistor of 1k ohm from the Gate to the Ground this is the pull-down that allows the Gate Voltage to be lower in value relative to Drain (assuming power is being applied to Drain).
- If you connect a 1N4007 diode in the Gate Bias path with the cathode connected to the Gate and the anode connected to Gnd, this will prevent there being reverse Gate Voltage when the power supply is reversed in polarity.
- Now connect the load (for example: LED + 470-ohm resistor, or an Arduino board using a similar circuit) between the Drain rail and GND.
- So when the power is applied with the correct polarity, the load (whether it be an LED or another load) will run as it should. If the power's polarity isn't correct, the load will not work.
MOSFET Method - Efficiency Calculation
To understand the efficiency advantage of MOSFET-based reverse polarity protection, consider the same 12V system operating at a load current of 500mA. Compared to diode-based protection, the MOSFET introduces significantly lower resistance in the current path, resulting in much smaller voltage drop and reduced power dissipation. This directly improves overall system efficiency and minimizes thermal losses, as shown in the following calculation.
Voltage drop = 0.5A × 0.1Ω = 0.05V
Power loss = 0.5A × 0.05V = 0.025W
Efficiency impact = (0.05/12) × 100% = 0.4% lossComparison: Diode vs MOSFET Reverse Polarity Protection
To clearly see the difference between diode protection and MOSFET protection, we can compare how both methods perform in real circuits. Even though both protect against wrong power connections, they differ in power loss, heat generation, and efficiency. The table below shows these main differences.
| Features | Diode Method | MOSFET Method |
| Voltage Drop | High (~0.6–0.8 V) | Very Low (~0.05–0.15 V) |
| Efficiency | Low | High |
| Heat Loss | High | Very Low |
| Cost | Cheap | Moderate |
| Current Handling | Limited | High |
| Reliability | Basic protection | More reliable protection |
Working Demonstration
In this video, both the diode-based protection circuit and the MOSFET-based protection circuit are tested to show their real-time behavior. When the power supply is connected correctly, both circuits allow current to flow and power the load. However, when the polarity is reversed, both circuits block the current and protect the connected components. The key difference can be observed in performance: the diode circuit shows a noticeable voltage drop and slight heating, while the MOSFET circuit delivers almost full supply voltage with very low power loss. This practical demonstration clearly shows why MOSFET-based reverse polarity protection is more efficient and reliable for modern electronic applications.
Enhanced P-MOSFET Reverse Polarity Protection with Zener Gate Clamping
The enhanced P-MOSFET reverse polarity protection circuit improves on the basic design by adding a Zener diode to protect the MOSFET gate from excessive voltage. In the simple MOSFET circuit, the gate voltage directly depends on the input supply. When higher input voltages or sudden spikes occur, the gate-to-source voltage can exceed safe limits and damage the MOSFET. The basic P-channel MOSFET reverse polarity protection circuit works well for supplies below ~20 V.
How the Zener Diode Protects the Gate
By adding a Zener diode, the gate voltage is clamped to a safe level, preventing overvoltage stress on the MOSFET. This makes the circuit more stable and reliable, especially in high-voltage or automotive and industrial applications. While the enhanced circuit uses one extra component, it provides better protection, improved durability, and safer long-term operation compared to the basic MOSFET-based reverse polarity protection circuit.
| Feature | Simple Circuit | Zener Protected Circuit |
| Reverse Polarity Protection | Yes | Yes |
| Gate Voltage Protection | No | Yes |
| Suitable for High Voltage | No | Yes |
| Component Count | Low | Slightly Higher |
| Reliability | Medium | High |
If you want to learn more about this enhanced circuit with the zener diode and see a detailed explanation, take a look at this article, “Reverse Polarity Protection Circuit”
How to Choose the Right MOSFET for Reverse Polarity Protection
Selecting the correct MOSFET for reverse polarity protection is critical for reliable and efficient operation. The following parameters should be checked from the datasheet before committing to a device:
| Parameter | What to Check | Recommended Value |
| VDS(max) | Must be greater than maximum supply voltage plus transient spikes | ≥ 1.5 × Vsupply |
| VGS(th) (threshold) | Must turn ON fully at your supply voltage; choose logic-level MOSFETs for 3.3 V/5 V | < Vsupply / 2 |
| RDS(on) | Lower is better — directly sets power loss and voltage drop | < 0.1 Ω for ≤5 A; < 0.01 Ω for ≥20 A |
| ID(max) | Must exceed peak load current with margin | ≥ 2 × maximum load current |
| VGS(max) | Determines whether a Zener gate clamp is needed | Typically ±20 V; add Zener if Vsupply > 15 V |
Real-World Applications of MOSFET Reverse Polarity Protection
The reverse polarity protection MOSFET circuit is a universal building block. The following applications benefit directly from the near-zero voltage loss it provides:
- Battery-powered devices
Protects gadgets when batteries are connected the wrong way. - Microcontroller projects
Keeps boards like ESP32 and Arduino safe during testing and development. - IoT and smart devices
Prevents damage in smart home sensors and automation systems. - Car electronics
Protects circuits in vehicles from accidental reverse battery connection. - Power supply inputs
Keeps adapters and power modules safe from wrong polarity connections. - Motor circuits
Protects motor drivers and controllers from wiring mistakes.
Conclusion
In conclusion, protecting circuits from wrong power connections is essential. While diode-based solutions work, they waste energy and generate heat. Reverse polarity protection circuit using a MOSFET provides a low-loss, efficient alternative that blocks reverse current, reduces heat, and extends battery life, making it ideal for both hobby and commercial projects. A well-designed reverse polarity protection circuit using a MOSFET resolves both issues: it conducts with a voltage drop of less than 0.1 V, generates negligible heat, handles high currents with the right device selection, and adds only two or three low-cost components to any design. Whether you are building a hobby project, a commercial IoT device, or an automotive accessory, P-channel MOSFET reverse polarity protection is the engineering best practice that every power input stage should include. Therefore, P-channel MOSFET reverse polarity protection should be considered a best practice in all power input stage designs, regardless of whether they are for a hobby project, commercial IoT device, or automotive accessory.
Frequently Asked Questions on Reverse Polarity Protection using MOSFET
⇥ 1. Can this circuit be used with batteries?
Yes, it is ideal for battery-powered devices because it reduces power loss and heat generation.
⇥ 2. Is MOSFET-based protection safe for high current circuits?
Yes, if the correct MOSFET is selected, it can safely handle high current loads.
⇥ 3. Can I use an N-channel MOSFET for reverse polarity protection?
Yes, you can use an N-channel MOSFET, but the circuit is more complex. It is usually placed on the ground side, and using it on the positive side requires extra control circuitry. For simple designs, a P-channel MOSFET is easier to use.
⇥ 4. Is it better to use a MOSFET instead of a diode for reverse polarity protection?
A MOSFET provides more efficient reverse polarity protection than a diode because its voltage drop is much lower (typically 0.05–0.15 V versus 0.6–0.8 V). This greatly reduces power dissipation and heat generation, especially in high-current applications.
Therefore, a MOSFET is preferable in battery-powered systems where efficiency and maximum available voltage are important.
⇥ 5. How can a P-Channel MOSFET be used to provide reverse polarity protection?
A P-channel MOSFET is placed in series with the positive supply rail for reverse polarity protection. With correct polarity, a negative VGS turns it on and allows current to flow. If polarity is reversed, VGS becomes positive, turning it off and blocking reverse current.
⇥ 6. Can this Protection Circuit Work with Arduino or ESP32 Boards?
Yes! Use a logic level P-MOSFET (e.g., AO3401, VGS(th) ≈ −1 V) on the 5 V or 3.3 V rail that powers the microcontroller board's VIN pin. The MOSFET will fully turn ON at these low voltages, provide only approximately 1-5mV of voltage drop, and completely protect the board from reverse power connection without any effect on the normal operation of the board.
⇥ 7. Why do some circuits include a Zener diode on the gate of a P-MOSFET?
MOSFET gates are typically limited to about ±20 V VGS, and voltage transients can exceed this rating. A Zener diode between gate and source clamps VGS to a safe value. This protects the MOSFET from overvoltage damage.
Related MOSFET Projects and Tutorials
Practical tutorials demonstrating how MOSFETs are used as efficient electronic switches for logic-level conversion, power control, and DC motor driving in embedded and general electronics circuits.
Simple MOSFET Switching Circuit – How to turn on / turn off N-Channel and P-channel MOSFETs
Discover how to use MOSFETs for switching circuits. Learn about N-channel and P-channel MOSFET behaviour, gate control, key parameters, and practical tips for reliable operation.
Simple H-Bridge Motor Driver Circuit using MOSFET
In this circuit tutorial, we will discuss one of the most commonly used and efficient ways to drive DC motors -the H Bridge circuit.
Arduino DC Motor Speed Control using MOSFET Transistor
Learn how to control the speed of a DC motor using Arduino and a MOSFET. This guide covers component selection, circuit setup, coding, and practical demonstrations for building an efficient motor controller.
Bi-Directional Logic Level Converter using MOSFET
Learn how to build a bi-directional logic level converter using MOSFETs to safely interface devices operating at different voltage levels, with step-by-step instructions and circuit explanation.
LogicTronix Stepping In Where FPGAs Beat CPUs, GPUs, and ASICs
FPGAs have become a recurring subject in recent CircuitDigest features, appearing in themes of education and accessibility. In our interaction with Krishna Gaihre, CEO & Founder at LogicTronix, an "AMD-Xilinx’s Selected Partner (ACP) for FPGA Design and ML Acceleration," we explored the practical side of things.
Voice Activated LED Controller with Touch Interface Using ESP32S3 Box 3
Voice control has become an integral part of modern smart home automation. In this tutorial, we build a voice-controlled LED system using the ESP32-S3-BOX-3 development board, combining wake word detection, speech recognition, touch interface, and audio feedback to create an intelligent control system. The code will be based on the factory example provided by Espressif and we will do the needed modifications to make it apt for our project.
The ESP32-S3-BOX-3 is a powerful development platform from Espressif that integrates a 320×240 touchscreen display, dual microphones for voice input, stereo speakers, and WiFi/Bluetooth connectivity. This project demonstrates how to leverage these features using the ESP-IDF (Espressif IoT Development Framework) and ESP-SR (Speech Recognition) library.
For a detailed hands-on review and getting-started walkthrough of the ESP32-S3-BOX-3 board, check out our previous articles on the same
Getting Started with ESP32-S3-BOX-3 - CircuitDigest Review
Programming ESP32-S3-BOX-3 with Arduino IDE - RGB LED Control
What You'll Learn
- Implementing wake word detection using WakeNet
- Building command recognition with MultiNet
- Creating a touch-based GUI using the LVGL library
- Playing audio feedback through the I2S interface
- Controlling hardware (LED) through GPIO
Components Required
| S.No | Component | Quantity |
| 1 | ESP32-S3-BOX-3 Development Board | 1 |
| 2 | RGB LED Module | 1 |
| 3 | Jumper Wires | As needed |
| 4 | USB-C Cable (for programming and power) | 1 |
Software Requirements
- ESP-IDF v5.5.2 - Espressif IoT Development Framework
- Python 3.12+ - Required for ESP-IDF tools
Circuit Diagram and Connections
The circuit connection is straightforward. We connect an external LED to GPIO 40 of the ESP32-S3-BOX-3 board through a current-limiting resistor. For the ease of demonstration, we have used the RGB LED module that came with the ESP32-S3-BOX-3. We will be using the DOCK accessory to connect the LED. Insert the ESP32S3-Box-3 into the dock. Connect the GND pin of the RGB Module to any of the ground points in the dock and any one of the anode pins to the G40 port in the dock. As already mentioned, if you are using a single external LED, connect the cathode of the LED to ground and the anode to the G40 through a current-limiting resistor. The image below shows the connection.
Here is the ESP32S3-Box-3 with the LED attached.
Project Setup Beginner's Guide
ESP-IDF Installation
This project requires ESP-IDF v5.5.2. For full installation and configuration instructions, refer to the official Espressif Getting Started Guide:
ESP-IDF Getting Started Guide (Official)
Then make sure to get our project file from our repo using git clone or manually downloading and extracting it to your preferred location.
git clone https://github.com/Circuit-Digest/Voice-Activated-LED-Controller-with-Touch-Interface-Using-ESP32S3-Box-3Project Configuration
1. Set up the ESP-IDF environment: Once you have properly installed and set up the ESP-IDF following Espressif's guide, on Mac or Linux systems, open a terminal and run the following command to set up the ESP-IDF environment. Make sure not to close the terminal once done, and any upcoming idf command has to be executed through the same terminal or command prompt. If you ever close the terminal, or when opening the project later, run this command first to set up the environment. This has to be done in each new section.
. $HOME/esp/esp-idf/export.shOn Windows PCs, you can directly run the ESP-IDF command prompt shortcut in the Start menu, created by the ESP-IDF installer.
2. Navigate to the project directory. The path you provide must be to the root folder of your project directory.
cd /path_to_your_project_directory3. Configure the project: The menu config option is used to change or reconfigure the project parameters. It is completely optional since all required properties are already configured. But if you need, you can use the following command to access the menuconfig options.
idf.py menuconfig4. Build the project: You can use the following script to build the project. When it's executed, the IDF will copy any required managed components to the project folder and build the project. If any error occurs, other than related to code, it is highly recommended to do a full clean and then build.
idf.py build5. Flash and monitor: the following command is used to flash the code to the ESp32S3-Box-3 and monitor the serial log. Make sure to connect the board to the computer before running the command. If the board is not detected, even after connecting to the computer, Press and hold the boot button and then press the reset button. Later, release the boot button and try to upload the code. Once uploaded with this method, make sure to reset the board manually once the code is uploaded.
idf.py flash monitorProject Structure Overview
For your reference, this is the file structure of our project. The Main folder contains all the source code, while the components folder contains unmanaged component libraries, and the spiffs folder contains all the image or audio files.
How Wake Word Detection Works
Wake word detection uses ESP-SR WakeNet, a low-power neural network engine that runs continuously in the background. The Audio Front-End (AFE), preprocesses audio from the microphone array. Sample rate: 16 kHz, 16-bit signed, 2 channels (stereo). Then the WakeNet Engine does the CNN-based wake word detection. The Wakenet framework continuously monitors the audio stream with low power consumption. It supports up to 5 wake words simultaneously. The wake word detection flow is as given below.
Microphone -> I2S -> AFE -> WakeNet -> Wake Detection Event
Detection Events
- WAKENET_DETECTED - Wake word detected; start listening for commands.
- WAKENET_CHANNEL_VERIFIED - Channel verified; ready for command recognition.
The following key functions are used for the wakeword detection and are called from main/app/app_sr.c.
- audio_feed_task() - Reads audio from I2S and feeds it to AFE
- audio_detect_task() - Processes AFE output and detects wake words
- app_sr_start() - Initialises AFE and WakeNet models
Available Wake Words
The project supports multiple pre-trained wake words. Configure them via idf.py menuconfig.
Navigation: idf.py menuconfig -> ESP Speech Recognition -> Load Multiple Wake Words
| Wake Word | Language | Config Key |
| Hi ESP | English | |
| Hi Lexin | Chinese | |
| Alexa | English | |
| Xiao Ai Tong Xue | Chinese | |
| Ni Hao Xiao Zhi | Chinese | |
How to Change Wake Words
Method 1 - Using menuconfig
1.Run idf.py menuconfig
2.Navigate to: ESP Speech Recognition -> Load Multiple Wake Words
3.Enable or disable desired wake words.
4.Save and rebuild: idf.py build flash
Method 2 - Modify Code
Wake word selection happens in app_sr.c:
// In app_sr_set_language() function (line ~235)
char *wn_name = esp_srmodel_filter(models, ESP_WN_PREFIX,
(SR_LANG_EN == g_sr_data->lang ? "hiesp" : "hilexin"));To switch the English wake word to "Alexa":
char *wn_name = esp_srmodel_filter(models, ESP_WN_PREFIX,
(SR_LANG_EN == g_sr_data->lang ? "alexa" : "hilexin"));Using Custom Wake Words
Requirements: A custom wake word model trained with ESP-SR tools, in ESP-SR compatible format, with sufficient model partition space.
1. Train a custom wake word using ESP-SR training tools (see ESP-SR documentation).
2. Place the generated model file (.bin) in spiffs/ or the model partition.
3. Enable the custom word in menuconfig: For eg, ESP Speech Recognition -> CONFIG_SR_WN_WN9_CUSTOMWORD
4 .Update code in app_sr.c:
char *wn_name = esp_srmodel_filter(models, ESP_WN_PREFIX, "customword");5. Rebuild and flash: idf.py build flash
How Speech Recognition Works
Speech recognition uses ESP-SR MultiNet, an offline command recognition engine that supports up to 200 commands without requiring cloud connectivity. Both English and Chinese are supported in the ESP-SR engine.
Wake Word Detected -> AFE Processing -> MultiNet -> Command ID -> Handler Action
Recognition States
- ESP_MN_STATE_DETECTING - Listening for a command
- ESP_MN_STATE_DETECTED - Command recognised
- ESP_MN_STATE_TIMEOUT - No command detected within timeout
Key Components
- Command Definition (app_sr.c) - defines the text and phoneme for each command
- Command Structure (app_sr.h) - struct holding cmd ID, language, text, and phoneme
- Recognition Process (audio_detect_task) - AFE processes audio, MultiNet analyses chunks, returns command ID via queue to handler
// Command definition array (app_sr.c)
static const sr_cmd_t g_default_cmd_info[] = {
{SR_CMD_LIGHT_ON, SR_LANG_EN, 0, "turn on light", "TkN nN LiT", {NULL}},
{SR_CMD_LIGHT_OFF, SR_LANG_EN, 0, "turn off light", "TkN eF LiT", {NULL}},
};How to Modify Commands
⇒ Step 1 - Add Command Enum (app_sr.h)
typedef enum {
SR_CMD_LIGHT_ON,
SR_CMD_LIGHT_OFF,
SR_CMD_MY_NEW_CMD, // Add your command enum
SR_CMD_MAX,
} sr_user_cmd_t;⇒ Step 2 - Add Command Definition (app_sr.c)
static const sr_cmd_t g_default_cmd_info[] = {
{SR_CMD_LIGHT_ON, SR_LANG_EN, 0, "turn on light", "TkN nN LiT", {NULL}},
{SR_CMD_LIGHT_OFF, SR_LANG_EN, 0, "turn off light", "TkN eF LiT", {NULL}},
{SR_CMD_MY_NEW_CMD, SR_LANG_EN, 2, "my new command", "mI nU kMnd", {NULL}}, // Add
};⇒ Step 3 - Add Handler Action (app_sr_handler.c)
case SR_CMD_MY_NEW_CMD: // Add your handler
ESP_LOGI(TAG, "My new command executed!");
// Your action here
break;⇒ Step 4 - Rebuild and Flash
idf.py build flash monitorAdding Multiple Commands
// app_sr.h - enum
SR_CMD_FAN_ON,
SR_CMD_FAN_OFF,
SR_CMD_SET_BRIGHTNESS_HIGH,
SR_CMD_SET_BRIGHTNESS_LOW,
// app_sr.c - command definitions
{SR_CMD_FAN_ON, SR_LANG_EN, 2, "turn on fan", "TkN nN fN", {NULL}},
{SR_CMD_FAN_OFF, SR_LANG_EN, 3, "turn off fan", "TkN eF fN", {NULL}},
{SR_CMD_SET_BRIGHTNESS_HIGH, SR_LANG_EN, 4, "brightness high", "brItns hI", {NULL}},
{SR_CMD_SET_BRIGHTNESS_LOW, SR_LANG_EN, 5, "brightness low", "brItns lO", {NULL}},Dynamic Command Addition (Runtime)
sr_cmd_t new_cmd = {
.cmd = SR_CMD_MY_NEW_CMD,
.lang = SR_LANG_EN,
.id = 10,
.str = "my command",
.phoneme = "mI kMnd"
};
app_sr_add_cmd(&new_cmd);
app_sr_update_cmds(); // Update MultiNet command listAPI Functions (app_sr.h)
- app_sr_add_cmd() - Add a new command
- app_sr_modify_cmd() - Modify an existing command
- app_sr_remove_cmd() - Remove a command
- app_sr_remove_all_cmd() - Clear all commands
- app_sr_update_cmds() - Update MultiNet with the current command list
How Display and Touch Work
The project uses LVGL (Light and Versatile Graphics Library) for GUI rendering and touch input.
- Display Driver - ILI9341 LCD controller (320×240), SPI interface, RGB565 colour format, hardware-accelerated rendering.
- Touch Driver - GT911 capacitive touch controller via I2C, with multi-touch support (single touch used in this project).
- LVGL Integration - LVGL runs in a dedicated task with double buffering for smooth rendering. Touch events are handled via the LVGL input driver.
Initialisation (main.c)
bsp_display_cfg_t cfg = {
.lvgl_port_cfg = ESP_LVGL_PORT_INIT_CONFIG(),
.buffer_size = BSP_LCD_H_RES * CONFIG_BSP_LCD_DRAW_BUF_HEIGHT,
.double_buffer = 0,
.flags = { .buff_dma = true }
};
bsp_display_start_with_config(&cfg);
bsp_board_init();Creating GUI Elements
#include "lvgl.h"
#include "bsp/esp-bsp.h"
bsp_display_lock(0); // Lock for thread safety
lv_obj_t *scr = lv_scr_act(); // Get current screen
// Create a button
lv_obj_t *btn = lv_btn_create(scr);
lv_obj_set_size(btn, 100, 50);
lv_obj_align(btn, LV_ALIGN_CENTER, 0, 0);
// Add label
lv_obj_t *label = lv_label_create(btn);
lv_label_set_text(label, "Click Me");
// Add click callback
lv_obj_add_event_cb(btn, on_button_click, LV_EVENT_CLICKED, NULL);
bsp_display_unlock();Touch Event Handling
static void on_touch_event(lv_event_t *e)
{
lv_event_code_t code = lv_event_get_code(e);
lv_obj_t *obj = lv_event_get_target(e);
switch (code) {
case LV_EVENT_PRESSED:
lv_obj_set_style_bg_color(obj, lv_color_hex(0x0000FF), 0);
break;
case LV_EVENT_RELEASED:
lv_obj_set_style_bg_color(obj, lv_color_hex(0x00FF00), 0);
break;
case LV_EVENT_CLICKED:
light_ctrl_toggle(); // Perform action
break;
default: break;
}
}Supported Event Types
- LV_EVENT_CLICKED - Touch released after press
- LV_EVENT_PRESSED - Touch pressed
- LV_EVENT_RELEASED - Touch released
- LV_EVENT_LONG_PRESSED - Long press detected
Using Images in the GUI
The project converts BMP from images stored in an array using the image_to_c tool by bitbank2, to LVGL-compatible RGB565 format at runtime using bmp_to_lv_img() in light_ui.c. If you wan you can also use the LVGL image converter tool to convert the images to c array. One other option is to store the image files in the file system and load them from there.
lv_img_set_src(img_obj, "/spiffs/image.bin");Creating Custom GUI Screens
Here is an example code snippet showing how to create a new screen for the GUI. The LV object creation macro is used to create or define each screen.
// Screen 1: Main
lv_obj_t *main_screen = lv_obj_create(NULL);
// ... add widgets ...
// Screen 2: Settings
lv_obj_t *settings_screen = lv_obj_create(NULL);
// ... add widgets ...
// Navigate
void goto_settings(lv_event_t *e) { lv_scr_load(settings_screen); }
void goto_main(lv_event_t *e) { lv_scr_load(main_screen); }Warning: Each RGB565 pixel = 2 bytes. A 320×240 screen buffer = ~150 KB. Double buffering doubles that. Consider using PSRAM for large buffers.
For more details on how to use the LVGL library, please check out the official LVGL documentation.
How Audio Output Works
Audio output uses the I2S interface with an ES8311 codec chip for digital-to-analog conversion. The I2S Driver handles audio data transfer. Sample rate: 16 kHz default for SR feedback, 16-bit, stereo (2 channels). The ES8311 codec with I2S input provides analog output to the speaker and volume and mute control.
Audio Playback Flow
WAV File -> Memory Buffer -> I2S Write -> Codec -> SpeakerKey Functions (app_sr_handler.c)
- sr_echo_init() - Loads WAV files from SPIFFS to memory
- sr_echo_play() - Plays an audio segment via I2S
- bsp_i2s_write() - Writes audio data to I2S (BSP function)
Audio Playback Implementation
typedef enum {
AUDIO_WAKE, // Wake word detected tone
AUDIO_OK, // Command recognised tone
AUDIO_END, // Timeout / end tone
AUDIO_MAX,
} audio_segment_t;
// Load WAV from SPIFFS -> PSRAM
static esp_err_t load_wav_to_mem(audio_segment_t seg, const char *path)
{
FILE *fp = fopen(path, "rb");
if (!fp) return ESP_ERR_NOT_FOUND;
fseek(fp, 0, SEEK_END);
long sz = ftell(fp);
fseek(fp, 0, SEEK_SET);
s_audio[seg].buf = heap_caps_malloc(sz, MALLOC_CAP_SPIRAM | MALLOC_CAP_8BIT);
s_audio[seg].len = (size_t)sz;
fread(s_audio[seg].buf, 1, sz, fp);
fclose(fp);
return ESP_OK;
}Adding More Audio Playbacks
⇒ Step 1 - Add Audio Segment Enum
typedef enum {
AUDIO_WAKE,
AUDIO_OK,
AUDIO_END,
AUDIO_CUSTOM_1, // Add your segment
AUDIO_CUSTOM_2,
AUDIO_MAX,
} audio_segment_t;⇒ Step 2 - Add WAV File to SPIFFS
Place your WAV file in the spiffs/ directory. WAV requirements: uncompressed PCM, 16 kHz recommended, 16-bit, mono or stereo.
spiffs/
├── echo_en_wake.wav
├── echo_en_ok.wav
├── echo_en_end.wav
├── custom_sound_1.wav Add here
└── custom_sound_2.wav⇒ Step 3 - Load in Initialisation
ESP_RETURN_ON_ERROR(
load_wav_to_mem(AUDIO_CUSTOM_1, "/spiffs/custom_sound_1.wav"),
TAG, "load custom1 wav failed");⇒ Step 4 - Play When Needed
sr_echo_play(AUDIO_CUSTOM_1);⇒ Step 5 - Rebuild
idf.py build flashThe SPIFFS partition is automatically rebuilt with files from the spiffs/ directory.
Audio Format Requirements
| Parameter | Value |
| Sample Rates | 8, 16, 22.05, 44.1, 48 kHz |
| Bit Depth | 16-bit (recommended) |
| Channels | Mono or Stereo |
| Format | Uncompressed PCM WAV |
Converting Audio with FFmpeg
# Convert to 16 kHz, 16-bit, mono WAV
ffmpeg -i input.mp3 -ar 16000 -acodec pcm_s16le -ac 1 output.wav
# Convert to 16 kHz, 16-bit, stereo WAV
ffmpeg -i input.mp3 -ar 16000 -acodec pcm_s16le -ac 2 output.wavBSP Audio API Reference
The following BSP functions (bsp_board.h) control the audio codec:
| Function | Description |
| Set codec sample rate, bit depth, and channel mode |
| Set volume level (0-100) |
| Mute or unmute the audio codec |
| Write audio data buffer to I2S output |
| Stop the codec device |
| Resume the codec device |
Memory Considerations
- 16 kHz, 16-bit, mono -> ~32 KB per second
- 16 kHz, 16-bit, stereo -> ~64 KB per second
- 44.1 kHz, 16-bit, stereo -> ~176 KB per second
Recommendations
- Use PSRAM for audio buffers (MALLOC_CAP_SPIRAM)
- Pre-load frequently used sounds into memory
- Stream long audio files from SPIFFS in 4 KB chunks
Streaming Long Audio
void play_long_audio_stream(const char *wav_path)
{
FILE *fp = fopen(wav_path, "rb");
if (!fp) return;
fseek(fp, 44, SEEK_SET); // Skip WAV header
uint8_t chunk[4096];
size_t bytes_read;
while ((bytes_read = fread(chunk, 1, sizeof(chunk), fp)) > 0) {
size_t bytes_written = 0;
bsp_i2s_write((char *)chunk, bytes_read, &bytes_written, portMAX_DELAY);
}
fclose(fp);
}Changing the LED Pin
1. Open the file: main/app/app_led.c
2. Find this line (around line 15):
#define SINGLE_LED_GPIO GPIO_NUM_403. Change it to a different pin (e.g. GPIO 38):
#define SINGLE_LED_GPIO GPIO_NUM_384. Save the file.
5. Rebuild and flash:
idf.py build flash monitor6. Test: Connect your LED to GPIO 38 instead of GPIO 40.
Building & Flashing
Once the hardware is connected and the software is set up, follow these steps to compile and upload the code.
⇒ Step 1 - Navigate to the Project Directory
cd /path/to/esp32-box3-voice-led-project⇒ Step 2 - Activate ESP-IDF Environment
. $HOME/esp/esp-idf/export.sh⇒ Step 3 - Configure (Optional)
idf.py menuconfig⇒ Step 4 - Build
idf.py buildThis compiles all source files and creates the firmware binary. The first build may take several minutes as dependencies are downloaded.
⇒ Step 5 - Flash and Monitor
idf.py flash monitor*Tip: Press Ctrl+] to exit the serial monitor.
Final Result
After successfully flashing the firmware, the ESP32-S3-BOX-3 boots and displays the light control screen. Now we can control the LED with two different methods.
The first method is to use the voice commands. To use it:
1. Say the wake word: "Hi ESP" (speak clearly, about 1 metre from the device).
2. Wait for audio feedback - you'll hear a confirmation sound.
3. Speak the command: "Turn on light" or "Turn off light".
4. Observe: the LED changes state, the screen updates, and audio feedback plays.
5. Once the wake word is detected, you can continuously give commands without using the wake word. If you haven't provided any commands for a certain time(a few seconds), the ESP-SR engine will time out. To use it again, all you have to do is say the wake word again to trigger the wake word detection.
The second method is to use the touch screen. For that:
1. Touch the on-screen toggle button.
2. Observe: the LED toggles and the button image changes.
Here is the final result:
Troubleshooting
Wake Word Not Detected
- Speak louder and clearer, at 0.5-1 metre from the device.
- Reduce background noise.
- Check the serial monitor for AFE initialisation errors.
LED Doesn't Light Up
- Verify LED polarity
- Verify the GPIO 40 connection.
- Test with a multimeter: GPIO should read 3.3 V when ON.
Build Errors
- Ensure ESP-IDF v5.5.2 is correctly installed.
- Run . $HOME/esp/esp-idf/export.sh before building.
- Do a full clean rebuild: idf.py fullclean && idf.py build.
Touch Screen Not Responding
- Check the serial monitor for LVGL initialisation messages.
No Audio Feedback
- Ensure WAV files are in the spiffs/ directory before building.
- Check speaker volume (may need physical adjustment).
- Verify I2S initialisation in serial logs.
GitHub Link
Find the project’s codebase and documentation here. Explore, fork, and contribute on GitHub.
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