arthur_jordan05For you hardware hackers out there: there is now a custom replacement board for the SMA-Q2 based on the nrf52840 with a custom purely analog pulse sensor. If you manage to open the watch (it IS possible without breaking anything) it is quite easy to install. You'll have to leave out the plastic frame holding the battery. Firmware updates can be made over USB now...I've only flashed the current Adafruit bootlader right now and the thing shows up as a mass storage device. Not done any programming yet.
https://github.com/BigCorvus/SMA-Q2_replacement_board
https://github.com/BigCorvus/PulseSensor-for-SMA-Q2
Not sure whether this whole RTC-based power management stuff is really necessary since the chip can run on really nice low power modes, but this can also be omitted in future revisions. All basic housekeeping (LDO, charger, buttons, accelerometer, display connectors, vibration motor driver...) is in place and the dimensions are correct.
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This piece of hardware is actually independent from the firmware that emeryth is working on at the moment. The normal board in the watch is actually "open source enough".
This replacement board will require its own firmware. My goal was to create even more capable hardware by switching to the nrf52840 and to experiment with different heart rate sensors and accelerometers. Adding an RTC was also part of the plan. This is all highly experimental so I'd suggest sticking to the normal board at the moment
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Whoa this is super cool. Is the goal to make this software compatible with the normal board in this watch? Would also love to see what you've got so far in the NordicSDK firmware. I want to start hacking but ideally without spinning up a new project.
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