Blu is a small battery powered, Bluetooth device which can interface with many sensors via hot-swappable socket and visualize the readings with RGB LED and TFT screen. It also has a dedicated Android app - BLu Connect.
- Raspberry Pi Pico W
- TP4056 Li-Ion charger IC on J5019 module
- 0.96″ ST7735 TFT
- two TTP223 touch sensors
- RGB led
BLu uses custom version of MicroPython running the main Python firmware which handles Bluetooth and main functionality. UI/TFT drawing is implemented in C++ inside MicroPython fork, it uses custom version of TFT_eSPI and runs on second core of RP2040.
The main point behind decision to use Python was a great reduction of Bluetooth code complexity compared to using BTStack directly, as Python provides two more layers of abstraction on top of it: bluetooth and aioble.
The encosure for BLu was designed in Fusion360 and it was the first enclosure I ever designed. However the two biggest parts went out great on the first try. It was printed with PLA on Creality Ender 3 Pro. The deformations of the sensor plug are caused by excessive usage of a hot air gun while gluing the connector.
I should have though more about the wiring. The v2, which will probably never be built, should have a one or two connectors which would replace all the wires going between the two halves and also keep the two halves together like snaps.
This project started with a simple idea - to create a battery powered and Bluetooth capable device with proper enclosure which at least seems to be a finished product. Yes that's right, the plan didn't include any concrete functionality, because having it wouldn't make me learn anything more and would just slow the project down.