Programming ATtiny85 via Arduino Uno

• ATtiny Pin 2 to Arduino Pin 13 (or SCK of another programmer)
• ATtiny Pin 1 to Arduino Pin 12 (or MISO of another programmer)
• ATtiny Pin 0 to Arduino Pin 11 (or MOSI of another programmer)
• ATtiny Reset Pin to Arduino Pin 10 (or RESET of another programmer)

Configure the Uno as a Programmer: Examples -> ArduinoISP - Verify & Upload

Install the ATtiny board descriptions.

• Download the ATiny master.zip file from the link above.
• Unzip the attiny master.zip file. It should contain an “attiny-master” folder that contains an “attiny” folder.
• Locate your Arduino sketchbook folder (you can find its location in the preferences dialog in the Arduino software)
• Create a new sub-folder called “hardware” in the sketchbook folder, if it doesn’t exist already.
• Copy the “attiny” folder (not the attiny-master folder) from the unzipped ATtiny master.zip to the “hardware” folder. You should end up with folder structure like Documents > Arduino > hardware > attiny that contains the file boards.txt and another folder called variants.
• Restart the Arduino development environment.
• You should see ATtiny entries in the Tools > Board menu.

Now you can select 'Programmer -> Arduino as ISP'

Select the relevant chip and speed you require, select Tools -> Burn Bootloader to configure the chip (NB: this does not install a bootloader)

Now you can Verify & Upload programs as normal.

NB: This chip has a lot less program and ram space than an Uno, and is also limited in many other ways.

• You cannot use the normal Serial library, instead use SoftwareSerial
• The chip has only two PWM capable pins, for more use SoftPWM
• The chip has no i2c bus, but you can use TinyWire

Bath Thermometer software: bath_therm.ino