I'm following this tutorial, programming the ATtiny85 with an Arduino, using it to play some tones (through a piezo speaker). I'm struggling with getting the tones at the right pitch (I'm creating the wave forms manually, as the tone() function is unsupported on the ATtiny85).
I believe the problem may be down to differing clock speeds on the Arduino and ATtiny. I understand the clock speed can be altered on the ATtiny, how do I accomplish this using the arduino environment?
Answer
I believe the Arduino software (libraries and all) assumes you are operating at 16MHz. If you apply that assumption to the clock you are actually running at... things should work out. Assuming you are running the Tiny85 on it's internal oscillator I think it runs at 1MHz, so just multiply all your delay statements (and other notions of time) by 16.
If you need better accuracy than the internal oscillator provides you should think about using an external crystal or a resonator, but you will need to change the fuse settings of the AVR for that to work, and I think you will need a programmer like the AVRISP mkII to do that with AVR Studio (my recommendation).
I don't know much about the ArduinoISP sketch but to me it looks like it bit bangs the ISP protocol to upload a program to the target chip (not the on board Mega328), not sure it is equipped to manipulate fuses. ArduinoISP is documented here http://arduino.cc/en/Tutorial/ArduinoISP, fwiw. Note that you can't use a UNO currently to run the ArduinoISP sketch. It doesn't look to me like you can use the sketch to make the Arduino a viable interface for using the AVR Studio GUI tools.
EDIT: It looks like stuff has caught up and an UNO is viable for ArduinoISP now - thanks for the comments all
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