How to program ATTiny85 running 3.3V I have a working project built around ATTiny85 on a breadboard running at 5V. Now I want to move this prototype on a PCB where it will be powered from batteries. All components used are capable of running 3.3V so I want to run the ATTiny85 at 3.3V as well.

I don't have a programmer so I use ArduinoISP to program the ATTiny. If I change the fuses on Tiny to run it at 3.3V can I still use the 5V Arduino to program the tiny?

Since the ATTiny can easily run at 5V I don't see any problem with programming it at 5V levels and then run it at 3.3V. Is that correct?
Since the ATTiny can easily run at 5V I don't see any problem with programming it at 5V levels and then run it at 3.3V. Is that correct?


Yes. But if there are any components on the board that can't run at 5V then you must provide some way of protecting them from the excessive voltage.


  If I change the fuses on Tiny to run it at 3.3V can I still use the 5V Arduino to program the tiny?


There are no fuses required to change the actual operating voltage of the device. There is the BOD threshold, but you can still operate the device at a higher voltage without issue regardless.