Power-cycle request by EDBG protocol confuses Atmel-ICE and other debuggers

[felias-fogg]

Hi,

I finally figured out how to automagically power-cycle an XPLAINED-Mini board using the EDBG protocol. And it works perfectly fine. I thought I would be safe in using that in a try/except environment, but the other debuggers choked on it. After trying that unsuccessfully, the debugger is unresponsive afterward. My question is: Is there a way to find out beforehand whether the debugger can service the request? My current approach is to ask whether the product string of the transport device starts with 'mEDGB'. Is this the right approach or is there a more general solution?

Best regards,
Bernhard

[xedbg]

I guess you are referring to setting EDBG_CONTROL_TARGET_POWER to 0 and then 1 again?
(its been a while, sorry) I had no idea the debugger would choke on these calls when not supported... (that's a bug)
Some ideas:

• send a QUERY request to EDBG handler with EDBG_QUERY_COMMANDS and examine the list that is returned?
• have you tried a GET first, before SET?

[felias-fogg]

Hi,

Ok thanks, will try that.

[felias-fogg]

Hi, I tried your suggestion. The results are:

• Atmel-ICE (Version 1.45.7) throws an "AVR response timeout" on the EDBG-Set, -Get, and -Query commands. Afterward, you cannot connect anymore to it using, e.g., with pymcuprog (same error: "AVR response timeout"). You need to power-cycle to get it responsivce again.

• SNAP and PICkit4 (AVR mode) throw an "Index error" for all three commands, but they still work.

• XPLAINED-Mini 328P deals with the Set- and Get-commands in the expected way and returns the command list [0, 1, 2, 32, 33] when queried, and I wonder what these 32 and 33 commands could be ;-).

Best,
Bernhard

[xedbg]

Ah, you are going "next level" in detection here. Probably for the first time ever.
So, in theory, you should first query the root/discovery protocol for a list of command handlers, and if EDBG (0x20) is not in the list, then don't use it :) this should deal with atmel-ice and snap (at least I think this was the thought...)
Xplained Mini thus returns as it supports: query, get, set, getvoltage, setvoltage as expected.

[felias-fogg]

OK, will try that. Sounds reasonable.

The last sentence in your response is interesting. I went through the document and the Python scripts twice and found nothing. There are housekeeping commands for supply voltage control, but no EDBG commands. Unfortunately, the "set supply voltage setpoint" does not work with the Xplained Mini.