1. Xose Pérez
  2. solr




The Solr digital wrist watch is a clock that won’t work without a battery but it will neither work without sun. Even more: the vintage display is really cool but it’s hard to read outdoors. A complete nonsense.

Solr Watch

Check my blog post to know more about it: Solr: digital wrist watch


I strongly recommend to find some provider that can assembly at least the HMC5883L, it's a really hard to chip to solder manually. The rest of the components are quite easy to do.

BOM as exported from Eagle

Part Value Package Buy
C1 100nf C0805 .
C2 4.7uf AVX-A .
C3 220nf C0805 .
C4 100nf C0805 .
IC1 ATMEGA328P-AU-TQFP32 TQFP32-0.8-7X7MM Aliexpress
IC2 HMC5883L PLCC16-0.5-3X3MM Aliexpress / Ebay
LED1 HP QDSP-6064 Ebay
R1 82R R0805 .
R2 82R R0805 .
R3 82R R0805 .
R4 82R R0805 .
R5 2.2K R0805 .
R6 2.2K R0805 .
R7 4.7K R0805 .


Check the blog post above to connect an AVR programmer to the board.

The project is ready to be build using PlatformIO. Please refer to their web page for instructions on how to install the builder. Once installed:

> cd code
> pio run -e dev
> avrdude -v -p atmega328p -C avrdude.conf -c usbasp -Pusb -U flash:w:.pioenvs/dev/firmware.hex:i

Library dependencies are automatically managed via PlatformIO Library Manager.

Using PlatformIO to flash the board will probably result in an error since, by default, PlatformIO forces the -D flag on the compiler that skips the erasing process prior to flash the new project, then the verification will likely fail because out-of-boundaries memory positions will contain garbage data. That's why I'm compiling the code with PlatfomIO and flashing it directly using avrdude.