Based on optiboot, works with CV520 and MFRC522. Check optiboot.c#722 for actual differences between normal UART bootloader and this MFRC522 NFC bootloader.
Because sometimes you don't have physical access to the device's debug connectors but you still want to be able to reprogram it.
See: https://www.youtube.com/watch?v=Uo2WDgB-wPI
Build with:
make atmega164p SOFT_UART=1 UART=0 AVR_FREQ=8000000L BAUD_RATE=115200 LED_START_FLASHES=3 LED=A1 LED_DATA_FLASH=1
Erase device flash:
avrdude -v -patmega164p -cusbasp -e -B10
Program optiboot and fuses:
avrdude -v -patmega164p -cusbasp "-Uflash:w:optiboot_atmega164p_UART0_115200_8000000L.hex:i" -U lfuse:w:0xE2:m -U hfuse:w:0xD8:m -U lock:w:0xCC:m -B10
See: https://github.com/icedevml/avr-nfc-bootloader-app
Tested with ATmega-164PA, should work with any other microprocessor which is supported by optiboot, but you need to adjust Makefile.MCUdude manually for your microprocessor.
Please remember that values in secret.h.dist and pinout.h.dist are exemplary and you need to adjust them to match your setup.