ATTiny85 wont turn on, not sure how to debug

microcontrollerprogrammertroubleshooting

The ATTiny85 in the below circuit refuses to do anything.

$ avrdude -c usbtiny -p attiny85
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.    
avrdude done.  Thank you.

My setup:

  • Programmer: USBTiny ISP (Verified it works with an ATTiny with 0.1" pins in a breadboard that I could program just fine)
  • Environment: avrdude via OSX
  • Programmer interface: 6 header pins shoved into 6 pin ISP plug and inserted into offset programmer holes

I've verified:

  • ATTiny chip is mounted in the correct orientation, the dot lines up where it should.
  • Positive voltage (~4V from LiPo) exists between VCC and GND pins on the chip.
  • All traces from the ISP holes to the chip pins are connected where they should be.
  • Ceramic oscillator contacts connect with correct pins, and it's GND is grounded.
  • I can't find any shorts between discreet traces.

I've done everything I can think of and everything checks out. Except that my USBTinyISP programmer cannot talk to this chip. It acts as the programmer pins are not connected to anything.

Lastly, a previous iteration of this board seemed to work fine. That older board didn't include the LiPo charging circuit and it connected the ISP 5V+ pin to the power line (which shouldn't be required if the battery is powering the circuit).

  • Could my chip be bad?
  • What are the chances the ATTiny85 cap was put on backwards?

I'm out of troubleshooting ideas. What am I missing?

Project Schematic
Project PCB
Project Photo

Best Answer

Apparently, I had a bad chip! I swapped out the ATTiny85 with a spare and it booted right up. Weird. Perhaps the DOA rate of these chips are higher than I expected, or maybe I static discharged it somehow?

No idea, at least I'm glad I didn't miss something silly :)