STM32L4 Sensor Tile

From Kris Winer on


STM32L4 Sensor Tile

Small, connected device for smelling and hearing in any environment.

This is a 20 mm x 20 mm four-layer pcb tile full of interesting sensors (ICS43434 I2S Digital Microphone, MPU6500 acclerometer/gyro, BME280 pressure/temperature/humidity, and CCS811 air quality) with a Rigado BMD-350 UART BLE bridge for sending data to a smart phone all managed by a STM32L432 host MCU.

The STM32L432 is programmed using the Arduino IDE via the USB connector and serial data can be displayed on the serial monitor to verify performance and proper function, etc. But it is intended to be powered by a small 150 mAH LiPo battery for wireless sensing applications. The STM32L4 is a very low power MCU and with proper sensor and radio management it is possible to get the average power usage down to the ~100uA level, meaning a 150 mAH LiPo battery can run the device for two months on a charge.

A library for it is available on GitHub:


A collection of sketches to run the STM32L432-based (20 mm x 20 mm) sensor tile with an MPU6500 accel/gyro, ICS43434 I2S digital microphone, BME280 temperature/pressure/humidity sensor, and CCS811 air quality sensor. The sensor tile has an on-board MAX1555 LiPo battery charger, an on/off switch, and a Rigado BMD-350 nRF52 BLE module.




STM32L4 Sensor Tile


Patrick Van Oosterwijck created an audio BLE beacon that can be activated by the vision impaired to find exact locations of doorways, bus stops, crosswalks, and more:



The idea is that a blind person uses a navigation app, and can query to see “what is around”. In the list of beacons that are around, they can tap the one they want to know the location of and it will start to produce an audible signal for a short time.

The BLE module is configured as an iBeacon and allows connections. It has a battery service and an “Immediate Alert” (AKA “Find me”) service.

Patrick used the following to build the prototype:

  • A 550 mAh 3.2 V LiFePO4 cell
  • A #LiFePO4wered/Solar1 prototype to charge the battery
  • A 5.5V, 0.6W monocrystalline solar cell
  • A Silicon Labs (formerly BlueGiga) BLE113 module
  • A beeper that works very badly (better solution needed)
  • And a IP65 enclosure

xorbit has shared the booster for loud piezo beeper on OSH Park:



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