BRLTTY in Chrome OS

Chrome OS uses the open-source BRLTTY library to provide support for refreshable braille displays.

We typically ship with a stable release build of BRLTTY plus some cherry-picked patches.

Updating BRLTTY or adding a patch

First, follow the public Chromium OS Developer Guide to check out the source. At a minimum you'll need to create a chroot. You do not need to build everything from source. You do need to start the devserver.

Next, flash your device to a very recent test build. Internally at Google you can do this with the following command when the dev server is running, where CHROMEBOOK_IP_ADDRESS is the IP address of your Chromebook already in developer mode, and $BOARD is your Chromebook's board name.

cros flash ssh://CHROMEBOOK_IP_ADDRESS xbuddy://remote/$BOARD/latest-dev/test

The BRLTTY files can be found in this directory:


The first thing you‘ll need to do is edit the ebuild symlink to change the revision number. The real file is something like brltty-5.4.ebuild, but the revision will be something like brltty-5.4-r5.ebuild. You’ll need to increment it.

To increment it from r5 to r6, you'd do something like this:

rm brltty-5.4-r5.ebuild
ln -s brltty-5.4.ebuild brltty-5.4-r6.ebuild
git add brltty-5.4-r6.ebuild

The changes we make are all patches against a stable release of brltty. To add a new patch, put it in the files/ directory and reference it in brltty.bashrc

Once you're done adding patches or making other changes, flash it to your device like this:

emerge-$BOARD brltty
cros deploy CHROMEBOOK_IP_ADDRESS brltty

After that, reboot your Chromebook and verify that brltty works.

To upload a change, use repo, something like this:

repo start <branch_name> .
git commit -a
  TEST=Write what you tested here
repo upload .

Note that you shouldn't need to run cros_workon.