dl8dtl
commented
2 years ago because it implies that -F might fix it,. when it absolutely never would
You are probably too young then. ;-)
In the early days of the AVRs (and that's where all that including the message originate from), with those sometimes quite flakey self-built parallel-port ISP adapters, it could occasionally happen that you triggered an erasure of the signature fuses. This case is even mentioned in one of the old AVR appnotes. Likewise, I've got one AT90S1200 where I somehow managed it to reprogram the signature fuses to all 0's – even though that controller still functions normally.
That's why we invented -F as an override, and gave that hint in the error message.
Covering all the cases there which you mention is certainly way too much for a simple error message. In that case, it makes more sense to rewrite the error message into some kind of "please read the documentation", and then mention all possible cases in the FAQ.
You're welcome to make suggestions for that, preferrably as pull requests.
MCUdude
SpenceKonde
mcuee
per1234
More than any other error, this error leads new users astray. When using ISP programming on classic AVRs, and the signature doesn't match. a. If the signature reads as 0xFFFFFF we should report that the likely cause is a wiring error (MISO shorted to Vcc, GND not connected to target, etc b. If the signature reads as 0x000000, the most common case, we should report the likely cause either wiring, or that the user previously set the chip to a non-internal clock source which isn't present, and that supplying an 4-8 MHz squarewave to the XTAL:1 pin should allow it to be reprogrammed. c. Only if neither of the above is, we should print what chip we were expected, and what we saw, and mention -F
The reference to -F when it's reading as 0xFFFFFF or 0x000000 is misleading, because it implies that -F might fix it,. when it absolutely never would, because the problem is either MISO shorted high or chip set to use crystal or ext clock that isn;t present. We should mention workaround only when they might be helpful. Many relative newbies (based on what I read on forums) seem to get sidetracked by that note, and spend hours trying to figure out how to get that -F into the upload command, instead of finding the modified arduinoasISP that outputs an 8 MHz clock which can be used to revive 0x000000 chips that wound up that way due to incorrect clock setting.