Can I program the Romi 32u4 from the attached Raspberry Pi using AVRDUDE? It looks like I should be able to using the latest versio of AVRDUDE and connecting some GPIO pins from the Pi to the ISP pins on the Romi. Has anyone else tried this?
Yes, that is possible. I recommend connecting the Romi 32U4 to the Raspberry Pi via USB and then following the instructions in the “Programming using avr-gcc and AVRDUDE” section of the Romi 32U4 Control Board User’s Guide.
In general it is also possible to program AVRs using the GPIO pins of a Raspberry Pi, but I do not recommend it since you would have to make several extra connections and you would need to think about level shifting (the ATmega32U4 on the Romi 32U4 runs at 5 V).
But I am using the USB port on the 32U4 to provide power for both the 32U4 and the Pi, and I’m using the only USB port on the Pi for a WiFi dongle.
It looks like there are 4 level shifters on the Romi board and, if what I have read about 3.3v being enough for reset, sck, and mosi, I will only need one going 5->3 for miso.
I’m going to give it a try tomorrow. I’ll let you know how it goes.