Update of bug #42267 (project avrdude):
Status: None => Confirmed
Assigned to: None => joerg_wunsch
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Follow-up Comment #2:
This appears to be an issue with the JTAGICE3 firmware itself.
You are right in that it's certainly timing-related: even
adding -vvvv makes AVRDUDE slow enough to no longer trigger
the issue. If you sniff the USB traffic, you can see that
the wrong answer comes straight from the device, so AVRDUDE
itself is not at fault.
Btw., this happens for all the Atmel tools, ranging from
the AVRISPmkII through STK600, JTAGICE3 to the new Atmel-ICE.
Quite likely, they all use the same piece of firmware to
implement the ISP protocol. The only tool being different is
the JTAGICEmkII which works correctly.
So far, this used to have been masked off by the stk500v2
code using the old SPI_MULTI command for single-byte updates.
Starting with the JTAGICE3, this command is no longer supported,
so it had to be replaced using standard read/write commands in
AVRDUDE. Meanwhile, the code has been modified to always use
this (more modern) implementation, so this firmware bug becomes
apparent for all the tools. (Besides, that change "fixes" the
effect described in bug #21954.)
I'd tend to close the bug report as being "invalid" as it's
clearly a firmware issue with those tools. Adding arbitrary
delays just to accomodate for broken tools seems like a crock
to me, albeit it might be possible to do that.
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