[avr-chat] Using a custom ISP programming tool

[Sterling Peet]

     I think that I need to write/modify a programmer definition in avrdude to 
write the firmware into an AVR project that I am working on.  I would like to 
avoid re-inventing the wheel where I can, and I am interested in suggestions 
regarding where to start and how to approach this problem.

     I have inherited a project that contains virgin ATmega328 behind an FPGA 
that needs to be programmed.  I do not easily have direct access the to pcb 
hardware.  I do know how the FPGA is connected to the ATmega328, and the FPGA 
has access to the SPI and Reset lines for the ATmega328.  I also know how to 
communicate with the FPGA over a UDP socket.  Currently, the FPGA can 
communicate with the ATmega328 using either SPI or UART, but the communication 
between the computer and the FPGA uses 32-bit words.

    It is likely that I can convince the FPGA engineer to make small firmware 
changes, if that makes programming the ATmega328 firmware significantly easier. 
 Unfortunately, I do not have the full control of the hardware design that I am 
used to having, so my normal method of using a standard AVRISP header and 
programmer tool is not an option.

   The FPGA engineer has provided me a script that toggles the reset line and 
demonstrates FPGA interaction described in the firmware programming section of 
the ATmega328 data sheet, so I believe I should be able to write some 
relatively basic plumbing code to connect between avrdude and the FPGA to 
program the ATmega328.

   How should I proceed?  Are there any recommendations for this type of setup?

Thanks,

Sterling Peet

Embedded Developer
Gamma-Ray Camera Group
CTA Gamma-Ray Observatory Development
School of Physics & Center for Relativistic Astrophysics
Georgia Institute of Technology
837 State Street NW, Atlanta, GA 30332-0430