Using an Arduino Nano to program an ATtiny84a

Description: An Arduino Nano is first programmed to act as the default programmer that will then program the ATtiny84a to blink an LED ON/OFF.

Using an Arduino Nano to program an ATtiny84a

Notes: Before programming the ATtiny84a, make sure sure that no wire connections have been made to the ATtiny84a from the Arduino Nano. Plug the USB cable into the Arduino Nano and upload the “Arduino ISP” sketch as shown in the image below to the Arduino Nano.

Arduino as ISP

Next make all the wired connections from the Arduino Nano to the ATtiny84a as shown in the video on the bottom of this page and also connect a 10uF Capacitor to the Arduino Nano’s GND and Reset Pins.

Install the MCUdude MicroCore Library to the Arduino IDE, see more complete install instructions on this page:

  • Enter the following URL in Additional Boards Manager URLs

Then copy the below Arduino Code and upload it to the ATtiny84a using the Arduino Nano as a programmer (Arduino as ISP) as shown in the image below.



1 – Breadboard 400 Points
1 – ATtiny84a
1 – LED
1 – 220 Ohm Resistor
1 – 10uF Capacitor

Arduino Code:

#define led 1

void setup() {

 pinMode(led, OUTPUT);


void loop() {

digitalWrite(led, HIGH);
digitalWrite(led, LOW);

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