Earlier this week, we wrote about fake heart rate sensors found in ultra-low-cost fitness trackers as reported by Aaron Christophel. It turns out he also maintains an open-source project specific to P8 watch, PineTime, and other smartwatches compatible with Da Fit Android app: ATCwatch Arduino firmware.
The firmware provides a basic menu system, notifications, and the latest implementation enables direct HTTP or HTTPS GET requests to control IoT devices and get info from the Internet. The current firmware consumes about 150-200uA standby current, and last roughly 92 hours on a charge with heavy notification and usage.
While it’s possible to connect an SWD St-Link V2 to flash the bootloader and firmware, it’s not necessary, as it’s possible to flash ATCwatch Arduino firmware without having to open the watch by using over-the-air update function with DaFlasherFiles for PineTime or P8 watch together with DaFlasher Android app.
Once the update is done, you can get notifications on your phone after installing D6 Notification app. You’ll find several videos on Aaron YouTube channel with the latest on showing how to use HTTP/HTTPS from the P8 watch.
You’ll find more details and the Arduino C++ firmware on Github. If you own another watch that works with the Da Fit app, you should be able to modify the source code to adapt the firmware to the pinout of your device. If you need help porting the firmware to your watch, you could always join the relevant Discord server to get some support.