The Things Conference-2021 went virtual this year and we got to see many companies talking about their new products, providing insights on the LPWAN eco-system. STMicroelectronics was also a part of the event and we got the opportunity to have a small conversation with Mr. Benjamin Guilloud, the product line manager of the company about their STM32WL series of Microcontrollers. STM32WL, a long-range wireless microcontroller series from STMicroelectronics has gained immense popularity ever since the launch. Keenly interested in taking a deeper look into this controller, we asked Mr. Benjamin a few questions. He gave us the information on the new features that have been added to the STM32WL microcontroller, its compatibility, and how it's going to make an impact on the LPWAN community.
Q. Give us a brief intro on the STM32WL series of microcontrollers.
At the end of 2020, we hit the market with the latest version of our STM32WL System-On-Chip (SoC). In it, all the internal technical structure meaning the radio part, MCU, CPU, peripherals, etc. are embedded on the same silicon die, which makes this chip what we call a System-On-Chip. So, we are the first company in the world to hit the market with such a product and this brings much more integration.
Q. If we were to compare STM32WL with a discrete solution, what advantages do we have in terms of power consumption? Can you give us rough figures?
Even though everything is embedded in the same silicon die, the performance that can be reached with such a product is as good as what can be achieved with the standalone implementation. So, in terms of radio, for example, we could mention 92 milliamps in receiver mode, maybe 15 milliamps in the Tx mode, more than 10 dBm when using LoRa communication, 868 megahertz, or 87 milliamps at 20 dBm.
This is as good as what you could reach with a standard implementation and in terms of MCU power consumption, we have our usual power modes and our general-purpose microcontrollers are very famous for these. For example, in the framework of STM32WL, we’re able to reach one microamp. So, these are super useful to optimize your static power consumption. Also, as usual, we have a standby mode or shutdown mode. In standby mode, you can reach down to 70 nano amp. So this is super aggressive and helps device makers to extend the lifetime of the batteries in their applications, which is of paramount importance in the LPWAN worlds.
Q. It’s been a year since ST first announced its wireless long-range microcontroller series STM32WL, what new features have been recently added to this series?
At the end of 2019, we hit the market with the first version of the product with a single-core architecture based on ARM Cortex-M4. We recently hit the market with the latest version of it. The latest version is based on the dual-core architecture, based on the ARM Cortex-M4 and ARM Cortex-M0 cores. So, that brings advanced security features for various reasons.
There is secure hardware isolation in between the two cores, which leads to six levels of security, so much more flexibility in terms of secure implementation and there are other advanced security features what we call secure key management services, where users can benefit from flash memory area which is dedicated to the storage of objects or keys or any other objects, like protocol keys, for example, can be managed securely. You can deactivate new keys; you can securely move your object in the center inside the memory. We can think of other advanced features such as a secure firmware installer or secure firmware update.
It allows the companies to update or install the firmware for the first time from non-trusted manufacturing sites without any issue. It is very useful in the manufacturing context and provides double the hardware security features, such as AES hardware encryption through random number generators, etc. So, this latest version of STM32WL dual-core comes with advanced security features and much more flexibility for the users.
Q. What protocols does the STM32WL series currently support and what new protocol support can we expect down the line?
In the framework of STM32WL, there are multi-modulation capabilities viz. LoRa modulation capabilities, (G)FSK, (G)MSK, and BPSK modulations. With these multi-modulation capabilities, we can address the LoRaWAN protocol. For both of these protocols, we provide our embedded software package called STM32CubeWL.
The source codes for both of these stacks are available for free. Also with STM32WL, the multi-modulation capability is feasible, so you could even think of customers who would like to implement LoRaWAN protocol and Sigfox at the same time on the same device, all of this is feasible. You have full flexibility with this STM32WL because the platform itself remains always open.
Q. How does STM32WL manage to provide worldwide compatibility as the LPWAN frequency and power regulations are different for different regions?
Yes, there's a real need for worldwide compatibility chip. WL is worldwide compatible for several reasons. First of all, there's a linear frequency range from 100 megahertz up to 960 megahertz. So, you can target whatever geographic area that you want in the world. It is 868 in India and Europe, 915 in America, 923 in Asia, 470 in China; all of this is addressable with WL. Also, you need to take into account the power aspect, because the maximum level of power that can be used depends on the region as well. For this, we have a dual power output. One power output can go up to 22 dBm and in such cases, these can be used in America or China. There's also another power output that can go up to 15 dBm. In that case, search for output can be used in Europe. The main difference between the two power outputs is that one is more efficient in terms of power consumption but both of them are programmable from 0 to 22 dBm, or from 0 to 15 dBm for the second power output. This makes STM32WL worldwide compatible.
Q. How has the market response been for STM32WL so far? Which part of the market is adapting LPLAN fast?
Regarding the applications, we can clearly say that there is big traction from utilities and also from asset tracking and smart logistics. So, utilities with a smart water meter, gas meter electricity meters, etc., and in terms of security asset tracking in the smart logistics as well such as pallet trackers. With WL, we target all the current LPWAN vertical markets, in the smart home, smart agriculture, smart industries, smart citizen building, etc. In terms of geographic spread, there's a very good trend actually in all the regions. Of course, the size of the market is somewhat bigger in Asia but, overall the traction for WL is extremely good in all the countries.
Q. Tell us about the development ecosystem for STM32WL, does ST provide any tools, dev. Boards or stacks for developers to begin with?
On one hand, we have our hardware ecosystem where we provide some WL-based Nucleo boards. So the board number with Nucleo - WL55 JC1 or JC 2 depending on the region that you want to target. JC 1 will be used for America, Europe, and Asia, whereas JC2 will be used for China. These boards are available from distributors right now.
In terms of the software ecosystem, we provide some tools that can help designers from configuration up to flashing. These tools are available for free. For configuration, we have STM32CubeMX that can be used to configure the pinout of the chip and to automatically generate some code that is useful for prototyping the application.
In terms of IDE, we provide STM32CubeIDE, which is based on GCC compiler. We have partnered with IDE such as Arm-Tie or IAR. We also provide users with a tool called STM32CubeMonitor that can be used to perform RF advanced testing so that users can test their LoRa commands or test the modulations. Last but not least, there is also STM32CubeProgrammer so that users can flash their device. On top of this, we provide STM32CubeWL, which is an embedded software package containing plenty of application examples. We have made all of these free of charge for the customers as we want to enable a maximum number of users to help them through their developments.
For further information about STM32WL, please visit www.st.com/stm32wl
