STM32WL, the world’s first SoC with a built-in LoRa transceiver, accelerates the development of LoRa® IoT smart devices
MCUs come in various forms, and chip design has always followed this idea: by providing different cores, different memory capacities, different peripherals, and packaging options, to bring customers chip-level solutions that cover different applications. Since the launch of the first wireless MCU series STM32WB in 2018, STM32 has embarked on the path of wireless advancement..
LoRa is “seasoned”
LoRa is a long-range wireless transmission solution based on spread spectrum technology, belonging to one of the IoT communication technologies. It uses linear modulation spread spectrum, which can significantly improve reception sensitivity. LoRa stands for “Long Range,” with the main feature being long-distance communication.
LoRaWAN standard has established a complete ecosystem of LoRa chips, modules, base stations or gateways, network services, and application services.
The LoRa technology was initially developed by the French company Cycleo and later acquired by the American company Semtech, which developed a complete set of LoRa communication chip solutions based on LoRa technology, including different types of LoRa chips used in gateways and terminals. It is a new type of chip based on ultra-long-range low-power data transmission technology below 1 GHz. LoRa, with its astonishing sensitivity (-148dbm), strong anti-interference capability, and excellent system capacity performance, has gained widespread attention. LoRa has changed the balance between transmission power consumption and transmission distance, providing the industry with a new communication technology that can achieve long distance, long battery life, large system capacity, and low hardware costs, which is precisely what the Internet of Things (IoT) needs.
Semtech also initiated the establishment of the LoRa Alliance, which formulates and optimizes the LoRaWAN protocol. This large-capacity, low-power star network architecture and protocol can realize wireless wide-area networking. From the perspective of LoRaWAN’s network architecture, LoRa modulation technology is mainly used for data transmission between terminal nodes and gateways.
▲ LoRa’s network structure
Why integrate LoRa in STM32 MCU?
Why integrate LoRa?
As a complement to the STM32 RF connectivity product portfolio, the STM32WL system-on-chip integrates a general-purpose microcontroller and sub-GHz wireless control unit on the same chip,making it the world’s first wireless microcontroller to integrate a LoRa transceiver onto a SoC chip. Previously, the LoRa wireless solutions on the market were either discrete microcontrollers and transceivers or two components using the same package but different chips, i.e., system-in-package. The STM32WL empowers IoT applications by enabling simpler, more flexible, higher integration, and more energy-efficient designs.
▲ The seven major features of STM32WL bring you differences
The STM32WL microcontroller is built on the Arm® Cortex®-M4 core architecture, supporting multiple modulation modes including LoRa®, (G)FSK, (G)MSK, and BPSK, ensuring flexibility for wireless applications by adopting LoRaWAN® or any other suitable protocol in a completely open manner. The STM32WL microcontroller features sub-GHz radio capabilities based on Semtech SX126x, meeting the needs of various low-power wide-area network (LPWAN) wireless applications in industrial and consumer IoT.
With deep integration, the innovative open architecture of STM32WL is optimized for traditional/proprietary protocols of LoRaWAN®, enabling flexible resource utilization and efficient power management, helping to provide a better user experience while reducing BOM costs.
The STM32WL series is developed using the same technology as that implemented in the ultra-low-power STM32L4 microcontrollers, providing similar digital and analog peripherals for applications that require extending battery life and expanding RF range through sub-GHz transceivers. To ensure global compatibility, the STM32WL MCU provides dual power outputs and a wide linear frequency range to meet the needs of any unlicensed RF spectrum.
The STM32WLE5 series offers a wealth of communication-friendly peripherals and features, including up to 43 GPIOs, an integrated SMPS for optimizing power consumption, and various low-power modes to maximize battery life. Dual power outputs and a wide linear frequency range ensure global compatibility.
In addition to wireless and ultra-low-power features, the STM32WL microcontroller also includes embedded security hardware features, such as 128-bit/256-bit AES hardware encryption, PCROP read/write protection, and public key encryption using elliptic curve encryption engines.
▲ Performance of STM32WL
Overall, the STM32WL product is the leading product of the STM32 series in the sub-GHz wireless connectivity field, combining ease of use and reliability while perfectly meeting the needs of various industrial and consumer applications.
Why is STM32WL more flexible?
Dual power outputs and multiple debugging
The STM32WLE5 microcontroller complies with the physical layer requirements of the LoRaWAN® specification published by the LoRa Alliance®. Its supported modulation modes, including LoRa®, (G)FSK, (G)MSK, and BPSK, can also be used for traditional or proprietary protocols.
The STM32 series currently has five sub-series: STM32L0, STM32L1, STM32L4/STM32L4+, and the recently announced STM32L5, providing a complete solution for low-power applications. Apart from the STM32L5 based on the Arm Cortex-M33 core, which emphasizes security features, the other four series have their own strengths and can achieve quick porting.
▲ NUCLEO-WL55JC1
Why is STM32WL so efficient?
Architecture optimization and memory space
The STM32 currently has two wireless product series, the STM32WB which integrates a Bluetooth module and was launched in 2019, and the newly launched STM32WL, which benefits from the optimizations introduced in the STM32WB. Previously, engineers needed two 32 MHz external crystals: one to synchronize with the Cortex-M4 and the other for the LoRa transceiver; however, the architecture of STM32WL only requires one crystal to be used for both the MCU and the radio’s high-speed clock, helping to reduce BOM and simplify PCB design.
We optimize power management by including a switch-mode power supply (SMPS) and an LDO to shorten the wake-up time of STM32WL from any low-power mode. Preparing such an SMPS usually takes about 60 µs, but due to the presence of the LDO, even before the SMPS is ready, the MCU can wake up in 5 µs or less. When placing the STM32WL in sleep, stop, or standby mode, the system first uses the LDO and can begin processing information while waiting for the SMPS to be ready.
The STM32WL offers various memory options, including 64 KB, 128 KB, and 256 KB Flash, to meet the diverse application needs of developers while helping control costs. This allows teams to write software on larger test models without worrying about excessive resource consumption and then take the time to optimize the code to run on a smaller memory footprint.
The upcoming new version of STM32CubeMX will also make pin configuration simpler by placing the LoRa radio on the same chip as the STM32 MCU.
