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

  • \$\begingroup\$ Decoupling capacitors are conspicuous by their absence... \$\endgroup\$
    – Majenko
    Jan 6, 2015 at 18:41
  • \$\begingroup\$ Indeed. You might also try a new 't85 that has never been fused to depend on an external resonator. Once it has, it can't be programmed without a working clock. Beware that programming with 5v signals while supplying less is out of spec (and I have seen it cause damage) - though you may be able to fix that with series resistors as long as there is little on-board liading. It's probably worth modifying a board for external power as a test anyway - and beware of mistreating lipos. \$\endgroup\$ Jan 6, 2015 at 19:14
  • \$\begingroup\$ @Majenko, Indeed. Embarrassingly enough, I'm not sure when or where I would use decoupling capacitors. But the previous version of this board seemed to require no such thing. \$\endgroup\$
    – Alex Wayne
    Jan 6, 2015 at 19:17
  • \$\begingroup\$ @ChrisStratton this chip was virgin from a Mouser strip of parts. I'm not sure what the default fuses are (cause I can't read them), but I imagine they would default to the internal clock, right? \$\endgroup\$
    – Alex Wayne
    Jan 6, 2015 at 19:18
  • \$\begingroup\$ You can probably retrofit some smt caps on the prototype where power nets are on adjacent pins, such as your connectors. \$\endgroup\$ Jan 6, 2015 at 19:19

1 Answer 1


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 :)

  • \$\begingroup\$ It may the fuse programming. \$\endgroup\$
    – copper.hat
    Jan 6, 2015 at 20:49
  • \$\begingroup\$ Yes, most likely corruption of the fuses from a previous attempt. Though applying higher voltages than the supply to the pins - as you seem to be doing here - can also cause damage. \$\endgroup\$ Jan 6, 2015 at 22:31
  • \$\begingroup\$ Are you saying that using a fully charged LiPo at 4.2V and then using 5V logic form the programmer can cause damage to the chip? If so, I guess that's a good reason to connect the 5V power pin from the programmer to the chip, to bring the supply voltage up to match the logic voltage? \$\endgroup\$
    – Alex Wayne
    Jan 6, 2015 at 22:34

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