When you think "wearable" device, you probably think about something to attach to a person, maybe yourself! However, elektroThing came up with a new wearable idea. Tracer is wearable for things! Its onboard sensors can be strapped to an object and stream data over BLE to a mobile device.
"Have you ever wanted to stick an IMU on a thing to trace its pose and motion? Tracer provides reliable, high-performance, and cost-efficient tracking of objects for various applications." — elektroThing
The current Tracer version is a board that appears to be about 55mm by 50mm. You can use two effortless options to mount Tracer to an object. The first is slipping a velcro strap through the PCB's slotted cutouts. Three M2 connectors are the other securing method.
An ESP32-PICO-D4 is the core SoC. It provides 4 MB of Flash memory, Wi-Fi, and Bluetooth Low Energy (BLE) support. Additionally, the board contains an LSM6DSL IMU, a six-degrees-of-freedom (DoF) module from ST Microelectronics. Also from ST is a VL53L0X time-of-flight (ToF) sensor.
When powered by a coin cell battery, elektroThing expects Tracer to capture data at 100 Hz for up to 5 hours.
The example code uses the ESP-IDF toolchain. The recommended data path includes using a Madgwick Orientation Filter. This filter fuses the data from the IMU into a normalized output as Euler angles. But you should be able to program with Micropython and Arduino.
elektroThing recommends using Phyphox to capture the data from Tracer. Phyphox is an Android and iOS app that communicates with BLE and can accept various sensor input types. The app graphs data directly on the mobile device. Currently, there is limited support for Android to output via Bluetooth.
If you are interested in strapping one to an object, check out the Tracer project page. The GitHub repo only has a schematic and some code, but elektroThing says the complete design files will be available soon. Also, another revision is in the works that should make Tracer's PCB even smaller than it is now!