Multi-purpose wearables: a makers' dream come true

January 27, 2016 // By Julien Happich
With the CPRO version of its MetaWear sensing platform now raising funds on Kickstarter, Californian startup mbientlab is providing makers a Bluetooth-connected remote sensor on steroids.

Only 3mm thick (CR2032 coin battery included) and 24mm in diameter, the open-source ambient sensor board measures acceleration, angular velocity, magnetic field, pressure, altitude, temperature and ambient light.

Designed around Nordic Semiconductor’s nRF51822 SoC (featuring a 32-bit ARM Cortex M0 CPU) the device has enough on-board flash memory to log up to 15,000 sensor data entries before they are downloaded to a smartphone via the Bluetooth Low Energy radio module. Because the sensor unit is over-the-air programmable and updatable, controlled and programmed through a smartphone, it can be repurposed instantly, from one application to the next, as the ultimate wearable sensor.

Rather than being yet another mote hardware nicely packaged and marketed for one or two dedicated applications, the CPRO is open to feed any app with its versatile sensing capabilities.

The sensors on the BOM list include a LTR-329ALS ambient light sensor from LiteON, with a full dynamic range from 0.01 lux to 64k lux (16-bit resolution), a Bosch pressure and temperature sensor with redundant thermistor, and a 9-axis combo sensor from Bosch integrating an accelerometer, a magnetometer and a gyroscope. Interfacing pins include a PWM pin, an I2C interface and four Analog/Digital general purpose I/O pins which could serve to attach additional sensors. A LED indicator and a push button switch mounted on the board complete the tiny unit.

To make their product the most versatile and easy to integrate, the engineers at mbientlab offers a complete 3D MCAD model for download so users can make their own case. In its MetaWearCPSv0.5 datasheet, the company proposes further options such as fitting a Bosch BME280 digital humidity sensor, an ams TSL26711 optical proximity sensor or an ams TCS34725 RGB colour sensor.

According to the designers, the integrated power management circuit ensures battery will last up to several months.

In the last 2 years, the startup has successfully crowdfunded two previous generations of BLE-connected sensor boards, raising over USD 115,000