App Downgrades

This page documents the steps for downgrading the display-app to an earlier version.

Reasons to Downgrade

Downgrading the app should not normally be necessary, and it is generally discouraged.

However, there are a few scenarios in which it makes sense:

1. To see if a recently observed bug is present in older versions
2. To test backwards compatibility of the software update processes with older versions
3. To observe how a feature used to work in older versions

Downgrade Steps

Downgrades cannot be done via OTA because only the latest app version is available via OTA at any given time. You must use a USB instead.

1. Get the app package for the desired version. For Yocto, you’ll need the .deb package. For Buildroot, you’ll need the .ipk package.
   • If you are on Yocto, the minimum version that can be downgraded to is 2.0.0
2. Put the package in the updates/all folder on your USB.
3. Plug the USB into the display, then refresh the available updates on the Update Software page. You should see the USB package.
4. Follow the regular app update process: select the package, click Update, and wait for installation to finish, then cycle power.
5. If you are downgrading across major versions, you may run into a backwards compatibility issue. Here are steps to fix known issues:

   • >=3.0.0 to <3.0.0: removes some necessary environment files, which will prevent the app from showing onscreen. Run the following commands to fix, then cycle power:

     mount -o remount,rw /
     cp /etc/profile.d/0-mrsdisp.profile /etc/profile.d/bam-mrsdisp.profile
     cp /etc/profile.d/0-tslib.profile /etc/profile.d/bam-tslib.profile