Repo Manifests for building OpenAVR Example Images

This repository provides the glue for fetching all of the git repositories that are needed for building example images for the following boards:

• RaspberryPi 4 board
• Beagle Bone Black (revC)
• Beagle Bone AI

Getting Started

1. Install Google's Repo command.

   Download the Repo script:

   $ curl http://commondatastorage.googleapis.com/git-repo-downloads/repo > repo
   $ chmod a+x repo
   $ sudo mv repo /usr/local/bin/
   

   NOTE: If you are using Ubuntu-18.04 or newer, you can install repo with:

   $ sudo apt-get install repo
   

2. Initialize a Repo client.

   Create an empty directory to hold your working files:

   $ cd ${HOME}/${WORK_DIR}
   $ mkdir yocto-openavr
   $ cd yocto-openavr
   

   NOTE: Use whatever you want for ${WORK_DIR} and/or yocto-openavr, just adjust what follows accordingly.

   Tell Repo where to find the manifest:

   $ repo init -u https://github.com/openavr/manifest-openavr -b main
   

   A successful initialization will end with a message stating that Repo is initialized in your working directory. Your client directory should now contain a .repo directory where files such as the manifest will be kept.

3. Fetch all the repositories:

   $ repo sync
   

4. Initialize the Yocto/OpenEmbedded Environment:

   $ source ./setup-env-${TGT}
   

   This copies default configuration information into the build/conf directory and sets up some environment variables for OpenEmbedded. You may wish to edit the configuration options at this point.

5. Build an image.

   This process downloads several gigabytes of source code and then proceeds to do an awful lot of compilation so make sure you have plenty of space (100GB minimum).

   $ bitbake core-image-openavr
   

   If everything goes well, you should have a compressed root filesystem tarball as well as kernel and bootloader binaries available in your work/deploy directory. If you run into problems, the most likely candidate is missing packages. Check out http://www.yoctoproject.org/docs/current/yocto-project-qs/yocto-project-qs.html#resources for the list of required packagaes for operating system. Also, take a look to be sure your operating system is supported: https://wiki.yoctoproject.org/wiki/Distribution_Support

   TIP: You can have bitbake pre-download (or fetch) all of the source files needed for an image before starting to compile anything with the following:

   $ bitbake -k core-image-openavr --runall=fetch
   

   TIP: The first time you do a bitbake build, use the -k option to force the build to continue doing as much as possible after an error so that you can go away and do other work while the initial build is running (it can take a while). For example:

   $ bitbake -k core-image-openavr
   

6. Build an SDK for cross compiling target applications on an x86 machine.

   Run:

   $ bitbake -c populate_sdk core-image-openavr
   

   When this completes the sdk is in ./tmp/deploy/sdk/ as an .sh file you copy to the machine you want to cross compile on and run the file. It will default to installing the sdk in /usr/local, and you can ask it to install anywhere you have write access to.

Installation to SD Card

Writing the wic file to SD card with balena-Etcher doesn't seem to work.

TODO: Need to figure out why Etcher doesn't work.

Need to use bmaptool:

$ apt install bmap-tools
$ sudo bmaptool copy tmp/deploy/images/raspberrypi4/*.wic.bz2 /dev/sdX

Staying Up to Date

To pick up the latest changes for all source repositories, run:

$ repo sync -d

Setup the Yocto/OpenEmbedded environment:

$ source setup-env

If you forget to setup the environment prior to running bitbake, your system will complain that it can't find bitbake on the path. Don't try to install bitbake using a package manager, just run the command above as bitbake will be installed by repo.

You can then rebuild as before:

$ bitbake core-image-openavr

Starting Fresh

So it is borked. You're not really sure why. But it doesn't work any more.

There are several degrees of starting fresh (from least to most dire).

1. clean a package:

    $ bitbake <package-name> -c clean
   

2. clean a package (removes sstate):

    $ bitbake <package-name> -c cleansstate
   

3. clean a package (removes sstate and downloads):

    $ bitbake <package-name> -c cleanall
   

References

• https://layers.openembedded.org
• https://www.yoctoproject.org/documentation
• https://source.android.com/setup/using-repo