I've just realized, I miswrote the version number in my first post. I'm using Arduino v1.0 and "damellis-attiny-6bff522.zip" from here: http://hlt.media.mit.edu/?p=1695
I have been playing with the the Attiny85's with the arduino as ISP and managed to brick one
Arduino AVR High-Voltage Serial Programmer
Thanks for the link! I'll definitely need to build either that or the other Fuse Resetter I posted above.
So, I did some testing.
You can indeed write and compile code to use D5.
The problem is, the Arduino IDE appears to set the fuses for the ATtiny85 when you hit "Burn Bootloader".
Unfortunately, that erases any existing code on the Arduino and you're left with a blank and unwriteable ATtiny85. Doh!
My solution was to use AVRdude from the command line.
I looked up the fuse values from the boards.txt file
attiny45-8.name=ATtiny45 (internal 8 MHz clock)
After messing with AVR® Fuse Calculator – The Engbedded Blog for a bit, I found the correct high fuse value to disable the reset pin.
High fuse value to disable reset pin: 0x5F
I then compiled/verified my sketch, and grabbed the hex file from the Arduino IDE:
I created a BAT file to run AVRdude:
avrdude -P COM4 -b 19200 -c avrisp -p attiny85 -v -e -U lfuse:w:0xE2:m -U hfuse:w:0x5F:m -U efuse:w:0xFF:m -U flash:w:tm1640.hex
(Using ArduinoISP from v0023 on my UNO) I ran the bat file, and voila!
The RESET pin now functions as I programmed it to in the Arduino IDE!
Attempts to reprogram or reburn a bootloader failed, confirming the RESET pin is indeed disabled.