I'm using an UNO to program an ATtiny84 (SOIC) with Arduino as ISP, and I'm getting inconsistent results.
First, I was successful in programming one ATtiny with a simple blink program for testing. However, I can't seem to program another one. I get the following error: avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.
I think I might know the problem, but before taking a ton of time to test this out I'd like to get some feedback. For the successful case, the chip was connected to a single LED. For the unsuccessful case, the chip was connected to various other components (potentiometers, amplifiers). Can these other components possibly affect the ISP process? If a schematic would be helpful, I can provide that.
The app notes for the AVR chips recommend a series resistor on the SPI lines if there are other SPI devices present, to prevent conflicts of interest while you are trying to program. Perhaps there is something like this going on.
I'm not exactly sure what is considered a "SPI" device, but two op amps are connected to the SCK and MISO pins. I removed the dual op amp chip from the PCB and programming worked. However, the results were still a little inconsistent. Sometimes, I had to unplug the UNO and plug it back in for it to work correctly (the IDE said "programmer not responding")...any ideas about that?
Also, I'd really like to be able to program the attiny84 while the op amps are connected...will the series resistors make this possible? If so, where exactly should I place them?