Several months ago, I asked how to add (or where to get) Attiny13 to the list of boards in the Attiny package available in github: https://github.com/damellis/attiny In post 1.5 IDE, the package is installed by adding repo's JSON file to boards manager, as described in this post: https://arduino.stackexchange.com/a/23056/2955

Nowhere it says how to modify the files, not at all. And the package doesnot contain Attiny13 info.

The answer to my question was to do it myself and make a pull request. So ok, but how do I do it? I don't understand those files. The JSON file refferences some SHA-256 named zip files. That's hardly something that can be clearly and simply edited.

Can anyone tell me clearly what do I have to do to get Attiny13 working within that profile?

  • Did you manage to fit an Arduino core inside the smallish ATtiny13 ? :-O Dec 4, 2016 at 17:58

2 Answers 2


this is the official Arduino IDE 1.5 3rd party Hardware specification. It is still valid for 1.6.

It is probably lots easier to just copy past a similar board; rename the board ID and try.

Note that for a change in the boards.txt to be seen in the Arduino IDE you need to stop and start the Arduino IDE.

  • But where can I find the boards.txt file? Won't it get overwritten upon next update? Dec 4, 2016 at 18:55
  • 1
    The first part of the document is about the folder structure so that tells you where you can find the boards.txt. Unless you upgrade or deinstall and reinstall the boards.txt will not be overwritten. But it is always safe to have your own copy (for instance on github)
    – jantje
    Dec 4, 2016 at 22:44

You can easily add entries for the ATTiny13 to the IDE, but won't show in the same listing as damelis's ATTiny cores, as he hasn't added the ATTiny13 yet.

Here is what I have found for ATTiny13 Arduino core files, working with boards.txt, loading them into the IDE, etc. The boards.txt is all laid out, just drop it into your personal workspace per the directions provided.


How to install
Boards Manager Installation
This installation method requires Arduino IDE version 1.6.4 or greater.
Open the Arduino IDE.
Open the File > Preferences menu item.
Enter the following URL in Additional Boards Manager URLs: https://mcudude.github.io/MicroCore/package_MCUdude_MicroCore_index.json
Open the Tools > Board > Boards Manager... menu item.
Wait for the platform indexes to finish downloading.
Scroll down until you see the MicroCore entry and click on it.
Note: If you are using Arduino IDE 1.6.6 then you may need to close Boards Manager and then reopen it before the MicroCore entry will appear.
Click Install.
After installation is complete close the Boards Manager window.

This will get you quite a lot of functions, configurable clock speeds, etc. The readme for this project helped me quite a lot in understanding what is going on inside the box and how I can enable only the Arduino core functions that I want, to save space.

Microcore is based upon : sourceforge.net/projects/ard-core13/files/latest/

And both projects have code updates as of this summer.

For other ATTiny (I'm using an ATTiny85 sometimes since for some things I ran out of space on the ATTiny13)


This will get you: ATtiny 25 (8 pin)

ATtiny 45 (8 pin)

ATtiny 85 (8 pin)

ATtiny 24 (14 pin)

ATtiny 44 (14 pin)

ATtiny 84 (14 pin)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.