1. Setup

1.1. References

This guide is based on the NXP/Freescale Yocto Project User’s Guide (IMXLXYOCTOUG)

The instructions for setting up and building Linux in the Yocto Project were adopted to our products and the ARMSDK environment.

Documentation is available online at nxp.com.

i.MX Software and Development Tools

A list of helpful bitbake commands can be found here:

NXP/Freescale - Useful bitbake commands

A cheat sheet for bitbake:

Bitbake Cheat Sheet

1.2. Requirements

For Yocto a Linux Host Machine is needed.

Hint

The list of supported machines for your Build Host is available here: https://www.yoctoproject.org/docs/2.4.4/ref-manual/ref-manual.html#detailed-supported-distros

For this purpose Ka-Ro used to offer a Virtual Appliance, called ARMSDK VM, while this can still be used it’s not recommended anymore.

We now recommend to grab a solution from a provider of for virtual appliances like osboxes.org. Like these (recommended: devuan):

https://www.osboxes.org/devuan-linux/

https://www.osboxes.org/debian/

https://www.osboxes.org/ubuntu-mate/

An important consideration is the hard disk space required for the virtual appliance. It is recommended that at least 120 GiB is provided, if not 500 GiB.

Should there be not enough space in the VA solution it can always be extended by adding a new HDD to the VM and mounting from a general mount point into the directory structure of development user in the VA, e.g. here.

1.3. Host packages

The Yocto framework requires (build) dependencies, packages that need to be installed/available on the host system for the builds like documented herein to pass successfully.

Example for Debian based (e.g. Devuan / Debian / Ubuntu) distribution:

First of all update your local repository:

sudo apt-get update

Install essential Yocto Project host packages:

sudo apt-get install gawk wget git-core diffstat unzip \
texinfo gcc-multilib build-essential chrpath socat

i.MX layers host packages:

sudo apt-get install libsdl1.2-dev xterm sed cvs \
subversion coreutils texi2html docbook-utils \
python-pysqlite2 help2man make gcc g++ desktop-file-utils \
libgl1-mesa-dev libglu1-mesa-dev mercurial autoconf \
automake groff curl lzop asciidoc u-boot-tools

1.4. Upgrade git version

A git version of ≤ 1.8.3.1 has bugs which will break builds. Please ensure a current version of git is installed.

Check installed version:

git --version

Update your local repository if not already just done before:

sudo apt-get update

Hereafter an upgrade example for users of a VA’s with an older Debian (>Wheezy) like the the one Ka-Ro offered.

Upgrade to git version 1.9.1 on ARMSDK-VM v7 - Debian Wheezy:

sudo apt-get remove git
sudo apt-get install git-man/wheezy-backports git/wheezy-backports

1.5. Setting up git

After making sure the most recent git version (at least > 1.8.3.1) is available, as described above, the tool should also be configured.

The (non-root) user working directly with the sources needs to be defined. If not defined, either the git tool or the hereafter mentioned repo tool will call this irregularity to the attention of the user. A proper setup is a requirement for the handling of the sources as governed by the git VCS, as git uses these information in conjunction with its source management features.

Setup git with the commands below:

git config --global user.name "Your Name"
git config --global user.email "Your Email"
git config --list

1.6. Setting up the repo utility

Thus does the repo tool complement very well the layered nature of the Yocto Project, making it among other things easier for customers to either just generally expand or add their own layers to the BSP.

To install the repo utility, perform these steps:

mkdir ~/bin
PATH=${PATH}:~/bin
curl 'http://commondatastorage.googleapis.com/git-repo-downloads/repo' > ~/bin/repo
chmod a+x ~/bin/repo

1.7. Yocto Project Setup

The BSP Release directory contains a sources directory, which contains the recipes used to build, one or more build directories, and a set of scripts used to set up the environment. The Yocto Project layers are downloaded to the sources directory. This sets up the recipes that are used to build the project. The following example shows how to download the BSP recipe layers. For this example, a directory called karo-yocto-rocko is created for the project (usually under a directory like $HOME/projects/ is recommend).

Use the stable branch rocko:

mkdir karo-yocto-rocko
cd karo-yocto-rocko
repo init -u https://github.com/karo-electronics/karo-bsp -b rocko
repo sync

When this process is completed, the source code is checked out into the directory sources under the working directory (in example above karo-yocto-rocko).

Note

The above given repo command deviates from the standard command as to overcome an error (specifically a http 404 error) when using repo init. The standard command would be:

repo init -u https://github.com/karo-electronics/karo-bsp -b rocko

User should update the codebase periodically, which can be performed via the following command:

repo sync

After a prolonged timespan an update is strongly recommended.

If errors occur during repo initialization, try deleting the .repo directory and running the repo initialization command again.

1.8. Choosing a machine

This release supports the following machines. Depending on the target to be compiled choose the machine configuration that matches your TXCOM module.

Note

The user has to differentiate between payload software, like the operating system (GNU/Linux), and the bootloader (U-Boot), thus there are in below given table two different settings for MACHINE=.

Note

This is an effect for the BSP as the U-Boot bootloader requires a different toolchain to be compiled with.

MACHINE=	U-Boot MACHINE=	TXCOM number	TXCOM name
TX6Q
NAND Modules
imx6q-tx6-nand		TX6Q-1010	(Legacy)
	tx6q-1030	TX6Q-1030	TX6Q/1000/1024S/128F
		TX6Q-1110	(Legacy)
	tx6q-1130	TX6Q-1130	TX6Q/1000/1024S/128F/LVDS
eMMC Modules
imx6q-tx6-emmc	tx6q-1036	TX6Q-1036	TX6Q/1000/1024S/8GF
TX6QP
eMMC Modules
imx6qp-tx6-emmc	tx6q-8037	TX6Q-8037	TX6QP/800/1GS/8GF/I
	tx6q-8137	TX6Q-8137	TX6QP/800/1GS/8GF/LVDS
TX6DL
NAND Modules
imx6dl-tx6-nand		TX6U-8010	(Legacy)
	tx6u-8030	TX6U-8030	TX6DL/800/1024S/128F/I
		TX6U-8110	(Legacy)
	tx6u-8130	TX6U-8130	TX6DL/800/1024S/128F/I/LVDS
eMMC Modules
imx6dl-tx6-emmc	tx6u-8033	TX6U-8033	TX6DL/800/1024S/4GF/E85
	tx6u-8133	TX6U-8133	TX6DL/800/1024S/4GF/E85/LVDS
TX6S
NAND Modules
imx6dl-tx6-nand	tx6s-8034	TX6S-8034	TX6S/800/256S/128F/I
	tx6s-8134	TX6S-8134	TX6S/800/256S/128F/I/LVDS
eMMC Modules
imx6dl-tx6-emmc	tx6s-8035	TX6S-8035	TX6S/800/512S/4GF/E85
	tx6s-8135	TX6S-8135	TX6S/800/512S/4GF/E85/LVDS
TX6UL
NAND Modules
imx6ul-txul-nand	txul-5010	TXUL-0010	(Legacy)
		TXUL-5010	TX6UL/528/256S/128F/I
eMMC Modules
imx6ul-txul-emmc	txul-5011	TXUL-0011	(Legacy)
		TXUL-5011	TX6UL/528/256S/4GF/E85
TX6ULL
eMMC Modules
imx6ull-txul-emmc	txul-8013	TXUL-8013	TX6ULL/800/512S/4GF/E85

Set the above given, depending on your intended workload, as value in the machine configuration variable:

MACHINE=<name-from-list-above>

1.9. Set up the environment

The command to setup the Yocto environment in its general form looks like the following:

MACHINE=<MACHINE> source ./setup-environment <build-directory>

Where the user has to insert a value, fitting the desired target TXCOM and software target, from the above table, and choose a name for the build directory to be created by the “setup-environment” script, to look like such:

GNU/Linux:

MACHINE=imx6dl-tx6-emmc source ./setup-environment build-gnulinux

1.10. U-Boot

MACHINE=tx6u-8033 source ./setup-environment build-bootloader

Note

The user has to differentiate between payload software, like the operating system (GNU/Linux), and the bootloader (U-Boot), thus there are in above given table two different settings for MACHINE=.

Note

This is an effect for the BSP as the U-Boot bootloader requires a different toolchain to be compiled with.

1.11. Choosing an image target

Choose an image target to build, e.g. (for more see below):

karo-image-minimal

This builds a minimal image consisting of:

• Kernel (Linux) incl. DTB (D evice T ree B lob)

• RFS (GNU)

u-boot

This builds an minimal image consisting of:

• Bootloader (U-Boot)

The RFS (short for: root file system, also: rootfs) in this instance is a low key file system generally intended for either first steps and/or headless systems. It includes all the general standard tools of a GNU/Linux distribution, but misses features like a X11 server, etc.

1.12. Additional packages

In Yocto layers provide recipes that provide packages, which themselves can either be specific programs (e.g. bash) or a suite of programs (e.g. Qt SDK). The before mentioned recipes define how these packages are baked (hence: bit **bake**) into the image.

Additional packages can therefore be added to images by providing an appropriate layer. A comprehensive listing of available, predefined layers can be found (e.g.) here:

https://layers.openembedded.org

1.13. Building an image target

bitbake <image>

Examples:

• For building core-image-minimal:

  bitbake karo-image-minimal
  

• For building Linux kernel and kernel modules only:

  bitbake linux-karo
  

• For building U-Boot only:

  bitbake u-boot
  

• A BSP with X server and GUI can be configured and built using:

  MACHINE=imx6q-tx6-emmc DISTRO=karo-x11 source ./setup-environment build-imx6q-tx6-emmc
  bitbake karo-image-x11
  

Note

To re-initialize the build environment when the session was exited, run the following command in the directory above the build directory:

source ./setup-environment <build directory>

1.14. Image Deployment

After a build is complete, the created image resides in the tmp/deploy/images sub-directory. An image is, for the most part, specific to the machine set in the environment setup. Each image build creates a U-Boot, a kernel, and an image type based on the IMAGE_FSTYPES defined in the machine configuration file.

The following files are created for Ka-Ro TX modules:

Filename	Content
u-boot-<machine>-<version>-.bin	U-Boot binaries
uImage	Kernel image
modules-<machine>.tgz	Kernel modules
<image>-<machine>.tar.bz2	RFS