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Creating a Linux Image for the Siemens IoT2000 Series

DMC

This blog was last updated on 4/13/2017. The process for generating the Siemens IOT2000 Yocto image may have changed.

The newly released Siemens IOT2000 series of controllers offer the flexibility of hobbyist Linux or Arduino platforms with the ruggedization necessary for industrial environments. The Siemens boards make use of the Yocto build tool for image creation. A sample image can be downloaded from the Siemens website (after logging in). However, for more involved projects it can be useful to modify the image to fit your application.

The README.md file in the Siemens IOT2000 example repository provides brief descriptions for what is required to build the image, but it can be confusing if you aren’t familiar with the Yocto build process. This guide is intended to clarify the process.

Getting Started

Before getting into the Siemens instructions, you’ll need to set up a build host. The Yocto Quick Start Guide has a detailed explanation of system requirements including available memory, Linux distribution, and available packages.

One of the layers required by the Siemens instructions has an additional dependency on the build host. You’ll need to install g++-multilib. On Debian based systems the command for this is:

Bash
dmc@dmc:/$ sudo apt-get install g++-multilib

Prepare

Once your system is set up, you’ll need to clone the poky Git repository. The current user’s home directory is usually a good place for this. 

Bash
cd ~

git clone -b krogoth git://git.yoctoproject.org/poky poky

You’ll then want to move into the poky directory that was created to clone the additional Yocto layers we will be using.

Bash
cd poky

git clone -b krogoth git://git.openembedded.org/meta-openembedded

git clone -b krogoth git://git.yoctoproject.org/meta-intel

git clone git://git.yoctoproject.org/meta-java

git clone git://git.yoctoproject.org/meta-intel-iot-middleware

git clone git://github.com/siemens/meta-iot2000

git clone -b krogoth git://github.com/imyller/meta-nodejs.git

The Siemens Git repository README.md recommends checking out specific commits of a few of these repositories:

Bash
cd ~/poky

git checkout yocto-2.1

git -C meta-intel checkout 9a06fc5bce05

git -C meta-openembedded checkout 247b1267bbe9

git -C meta-java checkout 9edf7d5aa5bd

git -C meta-intel-iot-middleware checkout 821cf14c8304

Configure

source poky/oe-init-build-env siemens-build

The following commands will create a directory called siemens-build and move you into that directory. It will also set up some configuration files in that directory. The next few steps will be editing those configuration files.

Bash
cd ~

source poky/oe-init-build-env siemens-build

Add needed layer to bblayers.conf 

The bblayers.conf file tells the Yocto tools where to find all of the repositories you checked out. If you used the commands in the instructions above, you just need to modify the file at ~/siemens-build/conf/bblayers.conf to look like the following (changes highlighted). Make sure to replace /path/to/ with the path to your user home directory.

Bash
# POKY_BBLAYERS_CONF_VERSION is increased each time
# build/conf/bblayers.conf changes incompatibly

POKY_BBLAYERS_CONF_VERSION = "2"

BBPATH = "${TOPDIR}"
BBFILES ?= ""

BBLAYERS ?= " \
  /path/to/poky/meta \
  /path/to/poky/meta-poky \
  /path/to/poky/meta-yocto-bsp \
  /path/to/poky/meta-openembedded/meta-oe \
  /path/to/poky/meta-intel \
  /path/to/poky/meta-java \
  /path/to/poky/meta-intel-iot-middleware \
  /path/to/poky/meta-iot2000/meta-iot2000-bsp \
  /path/to/poky/meta-iot2000/meta-iot2000-example \
  /path/to/poky/meta-nodejs \
"

Set MACHINE variable in local.conf

The instructions for this step are in the README.md for the Siemens IoT2000 BSP (Board Support Package) repository. The local.conf files sets parameters for any image that is built on your computer. Add the following line anywhere in the file at  ~/siemens-build/conf/local.conf

Bash
MACHINE = "iot2000"

Create example image

The bitbake command must be run from the ~/siemens-build directory with all of the environment that were set by the oe-init-build-env script. To be safe, I typically re-run the eo-init-build-env script before running bitbake. It will not overwrite your configuration changes. 

Bash
cd ~

source poky/oe-init-build-env siemens-build

bitbake iot2000-example-image

This command will take up to an hour the first time it runs.

Booting the image

If the bitbake command finishes without errors, it will generate a file at ~/siemens-build/tmp/deploy/images/iot2000/iot2000-example-image-iot2000.wic

This file contains the image created by bitbake. It is packaged in a way that it can be copied to an SD card and inserted into a Siemens IoT2000 device. You’ll need to insert an SD card into your computer and find where you can access it. The lsblk command is useful for this. Run the command before inserting the SD card. After the command has been run, insert the SD card and run the command again. The new device that shows up should be your SD card. 

Bash
dmc@dmc:~/siemens-build$ lsblk

Now that you know where the SD card, use the dd command to copy the contents of the .wic file to the SD card. In the following example, the SD card was enumerated as /dev/sdb.

Bash
sudo dd if=~/siemens-build/tmp/deploy/images/iot2000/iot2000-example-image-iot2000.wic of=/dev/sdb

This command can take a few minutes to execute and won’t generate any output while it is executing. Once the command is complete, you can eject the SD card and insert it into the Siemens IoT2000 device. Power on the device and connect over SSH.

Common Errors

In a previous version of this post, executing bitbake the first time would return with the following error. The issue has since been resolved in the meta-iot2000 repository.

Bash
ERROR: file-native-5.25-r0 do_fetch:
Fetcher failure:
Unable to find revision
f45db89ddc91692b662fffbabbdafc7bc4c00f5e
in branch master even from upstream

Yocto needs to know where to download source files for everything it builds. One of the locations defined in the meta-openembedded layer is no longer correct. The Krogoth release that the IoT2000 build process uses is from early 2016, so some of the references are out of date. The revision identified by f45db89ddc91692b662fffbabbdafc7bc4c00f5e is no longer valid and needs to be replaced with 789cfc7d727cee1c7cfb7d29c09162e2399285c5. We could make the change at the file ~/poky/meta/recipes-devtools/file/file_5.25.bb where this reference is defined. The Yocto reference documents recommend instead to create your own layer that overlays the existing layer, so the changes are more traceable. This procedure is as follows:

Create a new layer using the Yocto-layer tool:

Bash
cd ~/poky

yocto-layer create mylayer

You will be prompted with the following line. Just hit enter to accept the default layer priority of 6.

Bash
Please enter the layer priority you'd like to use for the layer:2[default: 6]

Hit enter again at the second line to skip creating an example recipe. 

Bash
Would you like to have an example recipe created? (y/n) [default: n]Show more lines

We would like to create an example bbappend file. So, at the following prompt, type y and hit enter.

Bash
Would you like to have an example bbappend file created? (y/n) [default: n] y

We want the new file to match the naming of the recipe file_5.25.bb we are fixing. So, at the next prompt, type file and hit enter.

Bash
Please enter the name you'd like to use for your bbappend file:
[default: example] file

At the next prompt, type the version number as 5.25 and hit enter.

Bash
Please enter the version number you'd like to use for your bbappend file
(this should match the recipe you're appending to):
[default: 0.1] 5.25

The final prompt reminds us to add this new layer to the bblayers.conf file.

Bash
New layer created in meta-dmc.
Don't forget to add it to your BBLAYERS (for details see meta-mylayer/README).

So, once again edit the file at ~/siemens-build/conf/bblayers.conf, adding the highlighted line:

Bash
/path/to/poky/meta-intel-iot-middleware \
/path/to/poky/meta-iot2000/meta-iot2000-bsp \
/path/to/poky/meta-iot2000/meta-iot2000-example \
/path/to/poky/meta-mylayer \
"

To make the changes that will fix the Error above, edit the file at ~/poky/meta-mylayer/recipes-example-bbappend/example-bbappend/file_5.25.bbappend

Delete the commented lines:

Bash
#
# This .bbappend does not yet do anything.
#
# Replace this text with modifications to the example_0.1.bb
# recipe (or whichever recipe you want to extend).
#
# Make sure the append filename matches the recipe name (PN)
# and version (PV) of the recipe being modified.
#

Add the line:

Bash
SRCREV = "789cfc7d727cee1c7cfb7d29c09162e2399285c5"Show more lines

Now the build should complete without errors.