What is it?

Arduino-compatible, USB-programmable, BLE-enabled, STM32WB55 development platform:

--64 MHz Cortex M4 MCU with 1 MB flash and 256 KB SRAM for application firmware, 30 GPIOs exposed to the user;

--Robust, power-and memory-efficient Arduino core written from scratch properly handling all errata with no gaps;

--Programmable using USB via the Arduino IDE or using ST-LINK and the SWD programming header;

--Embedded RF antenna for BLE (Arduino core supports both peripheral and central roles);

--On-board 16 MB QSPI NOR flash, 3-axis accelerometer, rgb led, battery voltage monitor;

--Small (20.5 mm x 50.8 mm), ultra-low-power (~2 uA sleep) development platform for breadboarding and prototyping.

From the data sheet: "The STM32WB5MMG is an ultra-low-power and small form factor certified 2.4GHz wireless module. It supports Bluetooth® Low Energy 5.0, Zigbee® 3.0, OpenThread, dynamic and static concurrent modes, and 802.15.4 proprietary protocols. Based on STMicroelectronics STM32WB55VGY wireless microcontroller, the STM32WB5MMG provides best-in-class RF performance thanks to its good receiver sensitivity and a high output power signal. Its low-power features enable extended battery life time, small coin-cell batteries or energy harvesting."

The highly-integrated STM32WB5MMG module is 7.3 mm x 11 mm with dual processors (64 MHz CM4 for application, CM0+ to manage BLE), 1 MByte flash memory and 256 kByte SRAM memory, embedded RF antenna with antenna matching, SMPS power management, LSE and HSE crystals, etc. Everything needed for basic operations is embedded within the module.

While the module supports up to 69 GPIOs, the small (20.5 mm x 50.8 mm) Sasquatch development board exposes 30 GPIO to the user including one I2C, two UART (one full duplex), two SPI, and one PDM ports. There are up to 16 interrupt-capable GPIOs, 6 PWM-capable GPIOs, and 12 ADC GPIOs. Some of these functions overlap (see pin map above). In addition, we have exposed the SWD (3 GPIOs) and USB (2 GPIOs) programming ports, and have included external QSPI NOR flash memory (7 GPIOs), led indication (3 GPIOs), one I2C sensor (3 GPIOs), a battery-voltage monitor (2 GPIOs), and an interrupt-capable user button (1 GPIO). So 51 of the possible 69 GPIOs are utilized in the Sasquatch design.

The Sasquatch development board has a Lumex SML-LX0303 rgb led, an ultra-low-power (< 1 uA always on) LIS2DW12 3-axis accelerometer on the internal I2C bus for wake-on-motion functionality, a 16 MByte MX25L12835FZNI QSPI NOR flash memory with disk drive emulation, a dual-FET LiPo battery voltage monitor, and Micro B USB connector for easy programming via the Arduino IDE. There is also a 2 x 5 SWD programming header for use with an ST-LINK for programming via STCubeMX or any other adult tool chain.

The 3V0 main power rail is sourced from either the 5 V USB voltage or battery voltage (3.0 V < Vin < 6.0 V) and the TPS7A0230PDBVR LDO provides up to 200 mA of continuous power with an Iq of just 25 nA. Two SBR05U20LPS Schottky diodes ensure that the highest power input wins; both battery and USB power sources may be connected at the same time. There is a dual n-type/p-type FET to monitor the battery voltage through a 2:1 resistor divider to limit current draw when not sampling. Lastly, a dual FET controls the flash memory power limiting the Sasquatch sleep current to that of the STM32WB5MMG module itself (~2.1 uA in STOP Mode 2, < 0.6 uA in STANDBY) when desired.

Why did you make it?

We wanted a robust, ultra-low-power Arduino-compatible platform for prototyping and testing project concepts that was fast enough (64 MHz), had enough flash and SRAM to run complicated programs, and was also BLE enabled to allow quick development of sensor nodes, environmental monitors, and other connected devices.

We exposed enough GPIOs and serial peripherals to offer flexibility and included the extra components (QSPI flash memory for data logging, low-power accel for wake-on-motion, battery voltage monitoring) we usually want in our more integrated, custom device solutions.

The development platform is small (20.5 mm x 50.8 mm) and is designed to easily fit on a small breadboard, making prototyping with sensor breakout boards, etc fast and easy.

We developed a custom Arduino core for the Sasquatch development board (STM32WB55VGY) to allow full and easy use of the available GPIOs and peripherals. The hard work of STM32L4 programming is embedded in the system layer that underlies the Arduino core allowing a few lines of C++ in an Arduino sketch to replace hundreds or thousands of lines of system level (i.e., Cube MX) C code.

Bottom line: we wanted something small like a Teensy development board but one with embedded BLE that could run with ultra-low power consumption. And that is Sasquatch in a nutshell!

What makes it special?

Small, ultra-low-power, ble-enabled development platform with enough GPIOs and features to be useful for custom project development.

Complete, robust, power- and memory-efficient Arduino core makes Sasquatch fast and easy to use. Allows you to spend your time on application development not system layer frustrations (i.e., gap-filling and errata work arounds, etc).

The Sasquatch schematics and BOM as well as Arduino core are open-source and freely available so you can prototype using the Sasquatch development board and then modify the schematics as needed for your custom application.

On-board QSPI flash memory, rgb led, and low-power, always-on 3-axis accelerometer allow a wide variety of applications (data logging, motion activation, state indication, etc) without additional components. Yet there are enough serial peripherals and GPIOs exposed to allow the addition of a large number of external devices as needed.