Arduino bootloader hacks and repository

Hi everyone,

I needed to flash my own bootloaders a few months ago and I quickly realised that its a pain to find what is out there. It seemed like Adaboot never got into a repository and then it was modified and people just had links to tarballs on their web sites.

So I finally found what I thought was the "latest" and was using that. But a few weeks ago I decided to make some modifications. So I threw it into a google code repository for better tracking:

You can either get the source from there, or you can grab a prebuilt 328 image. I needed to build both 16 and 20 mhz versions for my Lightuino LED Driver board so I threw them up there for all to use.

The major modifications I made are mostly useful for clones that require you to press the reset button to upload:

  1. PWM fade the pin 13 LED while waiting for a download. This way you know when you missed the window.
  2. Reset double-click. If you double click the reset button it waits for a download for a LOOONG time. This is really convenient when the board is not right next to the computer.
  3. A lot of code refactoring for size.
  4. All the Adaboot fixes and features of course.


Do most people here know what a code repository is?

There probably should be a section in the playground (if there isn't one already) with links to these bootloaders and such; you're right in that you have to hunt all around for such a thing, and you don't know what you'll get "in the end" - plus without a central place for things of this nature, they eventually get "lost" (people shut down their website, provider goes offline, etc).

Good idea, I'll put a link in the playground. And of course if other people have created bootloader variants -- in my digging I ran into some cool stuff -- I'd be happy to give you svn access and you can put it up there with mine. Of course, its not hard to create your own repository either... but as cr0sh says it might be nice to have them all in one place.

I also decide change adaboot but not use USART. This bootloader use software emulation of USART on any two pins.
Source here Arduino compatible loader without UART : X893

Interesting...I'll see if I can merge it in!

If you haven't found them, or haven't looked - make sure you get links in to the "small" bootloaders that have been developed (there are some 1K and under bootloaders for the 168/328 that I have seen - unfortunately I don't have the links handy - doh!)...


Please send me the links if you can dig them up -- I did a quick google search for "small arduino bootloader" and got nothing.


There is a 1K bootloader at

The magic incantation was "arduino 1k bootloader". :slight_smile:

Also, if you're really consolidating bootloader variants, user bhagman developed a very interesting bootloader that loads code from an SD card, no need to be conneted to the IDE to load a sketch.

Details at

This bootloader was recently posted - thought I would post here, because it sounds interesting (very tiny!):

thanks! Totally fascinating that after no bootloaders in the repo, there are now 2. I created my project Mar 19, he created his Apr 03! Wow.