Using CKOUT from an ATMEL MCU as an XTAL

For those who don't have an XTAL

Posted by Angel G. Miranda on January 15, 2018

What do you do when a microcontroller has its oscillator set as external and you don’t have an external oscillator? This guide will help you. Let’s do this!


1. Three ATmega328P-PU were purchased with an already programmed Arduino Bootloader.

1a. Therefore, fuses were already set to use an external 8MHz clock signal.

2. I don’t have an “X” MHz oscillator.

3. I have an ATtiny2313A with fuses set to use its internal oscillator of 8MHz.


AVR Studio version 4.19. Yeap, I am old school and, if you ask many experienced programmers, they would recommend version 4.19 over the new bloated versions. However, I guess you could still follow this guide if you have other versions.


  1. Breadboard
  2. Single thread wires
  3. An internal oscillator based microcontroller unit (MCU); in this case, it’s my trusty ATtiny2313A.
  4. The target MCUs that need an external oscillator to be programmed; in my case it’s the ATmega328P-PU with Arduino Bootloader.
  5. AVR in system programmer (ISP), duh.

Hardware Connections

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