At last year’s Embedded World conference in Nuremberg Germany, STMicro announced the release of the series of microcontrollers, the successor to the STM32L4 series of chips. However, it isn’t until now that it was available commercially. What’s the big whip you ask? Well, this wee powerhouse of a chip is packing both a 64 MHz Cortex-M4 and a 32 MHz Cortex-M0+ core as well as Bluetooth 5 and 802.15.4 radios. In short, it is an ultra-low power dual Arm Cortex core chip loaded with features and equipped with a full complement of IoT communications peripherals. With the M4 core running applications and the M0+ core handling communications, in effect, the chip can think and talk at the same time.

Based on an Arm Cortex‐M4 core running at 64 MHz (application processor) and a Cortex‐M0+ core at 32 MHz (network processor), STM32WB55 MCUs support Bluetooth 5 and IEEE 802.15.4 wireless standards.

Equipped with a generic 802.15.4 MAC layer you have the option of running a multitude of different WLAN protocols or even something proprietary if the need arises. For those not in the know, 802.15.4 is the IEEE standard for LR-WPANs (low-rate wireless personal area networks). The STM32WB55 is capable of running Bluetooth 5 and a WLAN protocol like OpenThread simultaneously.

The most important and generally interesting features include:

– A no crystal USB 2.0 interface (this means a lower parts count on BOM’s)

– Up to 72 pins can be used as GPIO

  • 1 — USART
  • 1 — LPUART (Low Power UART)
  • 2 — SPI buses
  • 2 — I2C buses

– Low power modes (essential for IoT devices)

– Multiple ADC’s (12 and 16 bit)

– Support for capacitive touch sensors

– An LCD driver

– A lot of embedded options (RSS, SFU, PCROP, PKA, AES, TRNG, CKS)

– 256 bytes to 1M of flash memory

– Up to 256kB of RAM

– Numerous timers and comparators

The actual list of features and peripherals is big, really big, and it depends on the chip package you are looking at. Check out the STM32WB Series overview page for more details. A development board called the P-NUCLEO-WB55 Development Pack is also available from STMicro or a number of distributers for about $42. The development pack actually comes with two STM32WB55 based boards. One of them is a development board, and the other is a USB dongle. Right out the box, you got two devices to test communications with.

The main development board and the USB dongle that comes with the P-NUCLEO-WB55 Development Pack.

The development kit is supported within the STM32Cube development ecosystem. Software libraries and example code are available, and there is IDE support for IAR Embedded, Keil, Arm Mbed, and GCC-based IDE’s. Incidentally, STM32Cube has an initialization code generator called STM32CubeMX. Code generators make the creation of a working program so much easier.

In addition, STMicro has the GUI-based STM32CubeMonRF software available. This is extremely handy because it gives use useful tools for testing the BLE and 802.15.4 radios. You can check the PER (Peak-Error-Rate), test the overall signal quality and setup custom scripts to handle specific tasks.

When you’re finished experimenting, and you’re to use the STM32WB55 as the cornerstone for your next project, the chips are available for about $3 and change. A complete list of distributors is available at the STM32WB55 series overview page.

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