ABSURD is a Python-based GDB remote server that allows GDB to interact with the on-chip debugger (OCD) of modern AVR microcontrollers via SerialUPDI.
ABSURD is licensed under the MIT License.

This project is currently at the proof-of-concept level. While it has been confirmed that basic GDB operations such as si and hbreak work on AVR128DB48 and AVR32EA48, many features are yet to be implemented, and some may not work properly even if implemented.

• SerialUPDI programmer (USB-UART adapter with its TX and RX connected by a fast diode)
• Modern AVR microcontroller with UPDI
  • MegaAVR 0-Series (ATmega__0_)
  • TinyAVR 0/1/2-Series (ATtiny__0_, ATtiny__1_, ATtiny__2_)
  • AVR Dx Series (AVR___DA__, AVR___DB__, AVR__DD__)
  • AVR Ex Series (AVR__EA__, AVR16EB__)
• pySerial Python library

• Clone this repository
• Install ABSURD with pip install -e .
• Connect MCU to PC with a SerialUPDI programmer
• avr-absurd -P [serial port] -p [MCU part name] -r [TCP port number]
  • or python -m absurd instead of avr-absurd if you didn't install ABSURD
• Run avr-gdb and connect to the server with target extended-remote :[TCP port number]

• Two hardware breakpoints
• Single-stepping
• Halt on jump/call instructions
• Halt on interrupts
• Read/write access to register file, RAM and peripheral SFRs
• Read access to flash

• NVM programming
• Software breakpoints
• Replace RspServer with something more decent

Those who may want to experiment with UPDI or OCD can import the absurd package.

• absurd.updi contains UpdiRevN classes, which implement raw UPDI instructions
• absurd.debugger.OcdRev1 wraps UpdiRevN and provides basic debugging functionalities. This may be helpful if you are coding your own debugger (to replace my terrible RspServer)
• My guesswork on OCD registers is available here.