Re: [avr-chat] avrdude : chip not responding

[Vincent Trouilliez]

Hi Joerg, Erik and Brian,

Thanks for all the suggestions, 8AM here, a new day of debugging is
about to start ! ;-)

I looked at the SCK line and it seems that qavrdude clocks the chip at
about 125KHz, so hopefully I won't need to use a 20cm cable ?!
I mean, the parallel port is obviously BEHIND the computer case, so I
need at the very least 75cm of cable so I can at least put the AVR board
in front of the computer case.
Anyway, yesterday I looked at the signals sent by avrdude withOUT the
avr being connected at all (removed from its socket...), thanks to the
-F option, and the shape of the signal on the MOSI line was truly
disastrous, and I could as disastrous signals on the MISO line ! But
avrdude isn't supposed to dirve the MISO line right ? It's 100%
dedicated to the AVR chip, right ? So if I see ANYTHING on this line,
then it has to be the MOSI and/or SCK lines that "pollute" the MISO
line... right ? So I guess my cable and/ord board arer not very clean !
Sadly I don't have any chemical product to clean teh soldering
"residues"...
I am getting tired of seeing crap signal, so I will unplug the cable,
and look at the signal stragiht from the parport connector of the PC,
using just two tiny bits of wires to help the scop's probe get in the
pin holes. If the signal aren't perfectly/decently square at this
point... :-/
I am thinking of adding Schmitt trigger buffers, but I have only TTL
(74LS), chips and at 125KHz, with no load or at a light (150Kohms)
resistive load, the high-level is nearer 4V than 5V, so I am unsure if
the AVR will reliably (if at all !) consider this as a valid signal !
Worse case, it will damage the input ! :-/
Must check the datasheet again...

Anyway, 8:15AM, a new day of debugging is now about to start...


Regards,


--
Vince