Skip to main content

Test programming the ATtiny85

Just got my ATtiny85 chip today from the postman and playing with it now.

There are quite a number of ways to program the ATtiny85, from the very cheap (USBasp, Tiny AVR Programmer, USBtinyISP) to the more expensive (AVRISP mkII). The Tiny AVR Programmer is probably the most convenient of the lot because it targets the ATtiny family specifically, so no cables are required. Just plug the chip into the provided socket.

Since I already have a spare Arduino Uno lying around, I am going the no-cost way, using the Uno to program the ATtiny85. You basically need to hook up the Uno to the ATtiny85 on a breadboard via 6 jumper wires. It's actually easier than it sounds, and took all of a couple of minutes to do.

Configuring the Uno to become an ISP

The next step is crucial. You need to upload a sketch to the Uno so that it has the necessary code to become an ISP. That's how you can then program the ATtiny85 through the Uno.

The first step is to load the ArduinoISP sketch from the built-in examples:

Make sure you have the board type selected as "Arduino Uno"

Now click "Sketch, Upload" and the upload should be completed without errors.

Installing ATtiny85 support

Under "File, Preferences", in the "Additional Boards Manager URLs" field, add this URL:

Then under "Tools, Board. Boards Manager...", type in "attiny" in the Filter field. You should see "attiny by David A. Mellis". Select and install.

Now that we have ATtiny85 support, under "Tools, Board", scroll to the end of the menu and select "Attiny 25/45/85".

Under "Tools, Processor", select "ATtiny85".

Under "Tools, Programmer", select "Arduino as ISP".

We are now ready to program the ATtiny85! Open up the sample "Blink" sketch:

 Change all references of LED_BUILTIN to 1. So the code looks like this:

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(1, OUTPUT);

// the loop function runs over and over again forever
void loop() {
  digitalWrite(1, HIGH); // turn the LED on (HIGH is the voltage level)
  delay(1000); // wait for a second
  digitalWrite(1, LOW); // turn the LED off by making the voltage LOW
  delay(1000); // wait for a second

Select "Sketch, Uploading Using Programmer" to upload the compiled sketch to the ATtiny85. Using "Upload Using Programmer" is important, as it indicates to upload the sketch through the Uno which we have setup as an ISP.

Once the sketch is successfully upload, we can connect a LED to the ATtiny85 (longer lead (+) to Pin 1, shorter lead (-) to GND) and watch it blink.

► Breadboard diagram created using Tinkercad.
► Source code formatted using ("manni" style).


  1. Arduino: 1.8.9 (Windows 10), Board: "ATtiny25/45/85, ATtiny85, Internal 1 MHz"

    Sketch uses 956 bytes (11%) of program storage space. Maximum is 8192 bytes.
    Global variables use 17 bytes (3%) of dynamic memory, leaving 495 bytes for local variables. Maximum is 512 bytes.
    avrdude: Yikes! Invalid device signature.
    Double check connections and try again, or use -F to override
    this check.

    An error occurred while uploading the sketch

    This report would have more information with
    "Show verbose output during compilation"
    option enabled in File -> Preferences.


Post a Comment

Popular posts from this blog

Update: Line adapter for Ozito Blade Trimmer

Update (Dec 2021): If you access to a 3D printer, I would now recommend this solution , which makes it super easy to replace the trimmer line. I have been using it for a few months now with zero issue.

3D Printer Filament Joiner

I have been looking at various ways of joining 3D printing filaments. One method involves running one end of a filament through a short PTFE tubing, melting it with a lighter or candle, retracting it back into the tubing and immediately plunging the filament to be fused into the tubing: One problem with this method is that you can't really control the temperature at which you melt the filament, so you frequently end up with a brittle joint that breaks upon the slightest bend. Aliexpress even sells a contraption that works along the same line. As it uses a lighter or candle as well, it suffers from the same weakness. I am not even sure why you need a special contraption when a short PTFE tubing will work just as well. Another method involves using shrink tubing/aluminium foil, and a heat gun: But a heat gun is rather expensive, so I wanted to explore other alternatives. The candle + PTFE tubing method actually works quite well when you happen to melt it at the rig

Attiny85 timer programming using Timer1

This Arduino sketch uses Timer1 to drive the LED blinker: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 /* * Program ATTiny85 to blink LED connected to PB1 at 1s interval. * Assumes ATTiny85 is running at 1MHz internal clock speed. */ #include <avr/io.h> #include <avr/wdt.h> #include <avr/sleep.h> #include <avr/interrupt.h> bool timer1 = false , led = true ; // Interrupt service routine for timer1 ISR(TIMER1_COMPA_vect) { timer1 = true ; } void setup() { // Setup output pins pinMode( 1 , OUTPUT); digitalWrite( 1 , led); set_sleep_mode(SLEEP_MODE_IDLE); // Setup timer1 to interrupt every second TCCR1 = 0 ; // Stop timer TCNT1 = 0 ; // Zero timer GTCCR = _BV(PSR1); // Reset prescaler OCR1A = 243 ; // T = prescaler / 1MHz = 0.004096s; OCR1A = (1s/T) - 1 = 243 OCR1C = 243 ; // Set to same value to reset timer1 to