Is there a list of stk500_getsync resp codes anywhere?

I'm trying to troubleshoot why an EL Sequencer board isn't flashing. Is there a list of error codes for stk500_getsync()? Or do the codes I see (0xc1 in this case) not really mean anything?

For example, here's the output this time (but it's been other numbers)

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xc1


It is not an error code. This is response from target and it doesn’t fit to expected byte. You can obtain more detailed info by switching on the verbose output for uploading.

Response all 0x00 or all 0xFF usually means some HW problem (cabel, wiring…). Other incorrect response than previous usually means incorrect board selection/setup.

I routinely see different resp for the same problem, and the same resp for different problems. The debugging value of the specific response value is near zero.

The useful ones are 0x00 or 0xff (usually hardware problem or chip not bootloaded and/or set to use a clock source that isn’t present), all responses the same and not 0x00 or 0xff (often indicates baudrate mismatch, ie, wrong board selected). The rest are just “something else”.