Update to using an ATtiny85 in a Similar Way To An Adafruit Trinket - specifically to run the Adafruit Neopixel library

September 15, 2015

I'm continuing to try and 'cheap-ify' my per effect cost for my Halloween decorations. I ran into some issues last night trying to get an Arduino sketch that used the Adafruit Neopixel library and ran on a Trinket to run on a straight ATtiny85. The solution was to select the chip in the Arduino IDE and using an AVR programmer, burn the 'bootloader'.

If you're following along (which of course you're not) - I added the ATtiny85 'board' to the ~/Documents/Arduino/hardware/tiny/avr/boards.txt file (in my OS X case). The 'board' is actually a description of the ATtiny chip and looks something like this (16Mhz):

###########################################################################

attiny85at16p.name=ATtiny85 @ 16 MHz  (internal PLL; 4.3 V BOD)

attiny85at16p.upload.tool=arduino:arduinoisp

attiny85at16p.upload.maximum_size=8192
attiny85at16p.upload.maximum_data_size=512

# PLL Clock; Start-up time PWRDWN/RESET: 1K CK/14 CK + 4 ms; [CKSEL=0001 SUT=00]
# Brown-out detection level at VCC=4.3 V; [BODLEVEL=100]
# Preserve EEPROM memory through the Chip Erase cycle; [EESAVE=0]
# Serial program downloading (SPI) enabled; [SPIEN=0]

attiny85at16p.bootloader.low_fuses=0xC1
attiny85at16p.bootloader.high_fuses=0xD4
attiny85at16p.bootloader.extended_fuses=0xFF

attiny85at16p.bootloader.path=empty
attiny85at16p.bootloader.file=empty85at16.hex
attiny85at16p.bootloader.tool=arduino:avrdude

attiny85at16p.build.mcu=attiny85
attiny85at16p.build.f_cpu=16000000L
attiny85at16p.build.core=tiny

Basically, all I believe that did was set the fuses correctly, but without too much digging, it didn't seem to be working when I manually set the fuses for the chip using avrdude. I'm not going to complain or dig much more now that it's working.

Incidentally, the setup (code) for the Neopixel library looks like this: