Problem synopsis: I've been working on a prototype project built on custom PCBs utilizing the ATTiny84. I have 3 separate prototype boards. Two have external power source (lithium battery with boost converter), one does not. Other than that they are all exactly the same. I have successfully programmed the tiny84's on these boards dozens of times each, and have not had problems. This evening I was writing new code and programmed one board, and there was a mismatch (sadly, didn't get a screenshot, but it was something like 0x00 != 0x01). I started over, and then began getting 'initialization failed' errors, which I was unable to account for or resolve.
Considering that my code may have (somehow?) damaged the chip, I switched to another known-good board and tried to simply reach the chip via avrdude with the following command:
avrdude -c usbtiny -p attiny84
I got 'initialization failed' on this board as well. Both boards are externally powered. So, moving on, I applied the jumper to my USBtinyISP and tried reaching the non-externally-powered prototype board. Same result. All three of these boards were able to accept programming earlier in the day, and no physical changes had been made since.
I have on hand some boards from a different project which use the ATTiny44, so I tried the same thing with these, and AVRDude was able to talk to this chip no problem. Likewise, I was able to communicate with an ATMega16 on another board.
It seems I only have problems programming the ATTiny84.
1. USBtiny from kit. I've used it hundreds of times successfully.
2. Windows 7 Pro. I've had no problems using this computer for AVR programming over the past several months
3. I'm using Atmel Studio 6, but programming via AVRDude. The target chip is ATTiny84.
4. The USBtinyISP has worked without problem for a few years (since 2007!)
5. The attached screenshot shows several failed attempts to reach my chip on 3 different boards, and then a successful attempt to reach an actual ATTiny44 on a completely different target board. As you'll see on the screenshot, I'm typing in ATTiny44, vice 84, but I should still get a message that there's a chip address mismatch if everything were working correctly.
6. I don't have a camera on hand, but the kit has worked without problem for years, and there is no visible damage or faults. The USBtinyISP can currently program an ATTiny44 or ATMega16, but not an ATTiny84.
Any ideas? I was on such a roll tonight, and then this came up