# ATTiny85 wont turn on, not sure how to debug

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?

• Decoupling capacitors are conspicuous by their absence... – Majenko Jan 6 '15 at 18:41
• 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. – Chris Stratton Jan 6 '15 at 19:14
• @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. – Alex Wayne Jan 6 '15 at 19:17
• @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? – Alex Wayne Jan 6 '15 at 19:18
• You can probably retrofit some smt caps on the prototype where power nets are on adjacent pins, such as your connectors. – Chris Stratton Jan 6 '15 at 19:19