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Topic: bootloader and the parallel port programmer (Read 1 time) previous topic - next topic

bigfun

I built one of those parallel port programmers following the instructions on
http://www.arduino.cc/en/Main/ParallelProgrammer
and, not looking carefully, I used 470K and 220K ohm resistors instead of the ones specified.  It didn't work, of course, and then I realized I only had 560 ohm resistors, not the 470 specified.  Interestingly, this made the programmer work, but unreliably. I'd get various numbers of flash errors - sometimes as few as eight and sometimes as many as 20 depending on how close I was to 470.  Eventually I found some 470s and it works most of the time but is still unreliable. I still get flash errors - always at least two.  If I try to flash several times and end on low number of errors the bootloader usually works and I can use it in the Arduino world.

Does anyone have any ideas for how to lower the error rate?  Should I be shielding the cables or something? Should I be using ferric cores?   I have no idea what speed the data is traveling at inside the programmer, though it must be some sort of serial system.
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mellis

If you're on Windows, you might need to change a registry setting to stop Windows from polling your parallel port.  See http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1142106610 for more details and some other things to try.

bigfun

I don't know what was going on with my parallel programmer - I resoldered it and it seems to be perfect now. Shielding and such were unnecessary. I guess I'd done a crappy solder job before.  All the those resistors are buried in epoxy now and it is perfectly reliable.
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