SolarCamPi

Detailed information at https://tbspace.de/solarcampi.html

BOM (PCB-RevC):
https://tbspace.de/content/downloads/ibom_solarcampi_revc.html

Firmware (PCB-RevB/RevC):
https://github.com/Manawyrm/SolarCamPi/tree/master/firmware

Schematic (PCB-RevC):
https://github.com/Manawyrm/SolarCamPi/blob/master/pcb/solarcampi.pdf

Raspberry Pi can flash the AVR, using avrdude with LinuxSPI support and inverted GPIO 17 as reset.

avrdude.conf configuration entry:

programmer 
  id       = "linuxspi";
  desc     = "Use Linux SPI device in /dev/spidev*";
  type     = "linuxspi";
  reset    = ~ 17;
  baudrate = 40000;
;

avrdude Usage to flash firmware:
avrdude -p m328p -P /dev/spidev0.0 -c linuxspi -U flash:w:firmware.hex

avrdude Usage to set fuses:
avrdude -p m328p -P /dev/spidev0.0 -c linuxspi -U lfuse:w:0xe2:m -U hfuse:w:0xd9:m -U efuse:w:0xfd:m