View source for CL-SOM-iMX7: Linux: Debian

== Overview ==
The example run-time Linux filesystem image for the CompuLab CL-SOM-iMX7 System-on-Module / Computer-on-Module is based on Debian GNU/Linux stretch.
The CompuLab Linux package for CL-SOM-iMX7 includes ready to run image, Linux kernel configuration and source code patches, and an archive of the root filesystem, used to create the image.

The default Debian GNU/Linux 10 image includes more than 400 software packages. Among them:

* Core system
* Debian package management system
* X11 Windowing System
* Xfce, LXDE, OpenBox desktop managers
* SSH server and client
* PulseAudio configuration and usage utilities 
* Bluez5 Bluetooth tools and daemons

The [[CL-SOM-iMX7: Linux: Automatic Installation|Automatic Linux installation on CL-SOM-iMX7]] page provides a brief introduction on how to install the run-time Linux image.
This article describes package structure and peripheral device options specific to the CL-SOM-iMX7.

{{Note|The article uses {{cmd|cl-debian}} hostname. A real hostname may be different.}}

== Using Debian Linux on CL-SOM-iMX7 ==

=== Connection and Logging In ===
{{:Transclusion: Debian: Logging In}}

=== Networking ===
{{:Transclusion: Debian: Networking}}

=== SSH Server ===
{{:Transclusion: SSH Server}}

=== Consoles ===
{{:Transclusion: Debian: Consoles}}

=== X Windows system ===
{{:Transclusion: Debian: X Windows: Xfce}}

=== Software Management ===
{{:Transclusion: Debian: Software Management}}

=== Analog Audio ===
CL-SOM-iMX7 provides an analog audio interface, which is registered as a standard ALSA sound card. 
Use {{cmd|aplay -l}} to list all soundcards and digital audio devices registered on the system:
<pre>
root@cl-rootfs:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: clsomimx7 [cl-som-imx7], device 0: 308a0000.sai-wm8731-hifi wm8731-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
</pre>
{{:Transclusion: Debian: CL-SOM-iMX7: Analog Audio}}

=== USB On-The-Go (OTG) ===
{{:Transclusion: Debian: iMX7: USB OTG}}

=== WiFi ===
{{:Transclusion: Debian: CL-SOM-iMX7: WiFi}}

=== Bluetooth ===
{{:Transclusion: Debian: CL-SOM-iMX7: Bluetooth}}
{{:Transclusion: Debian: iMX7: Bluez5 PulseAudio}}

=== Controller–area network (CAN) ===
CL-SOM-iMX7 features two Flexible Controller Area Network (FLEXCAN) modules. Each FLEXCAN implements full CAN protocol version 2.0B and supports both the standard and the extended frame format as well as a programmable data bit rate up to 1Mbit/s.
{{Note|Please prepare the hardware as described in the [[CL-SOM-iMX7: Evaluation Kit: Hardware Guide#CAN | CL-SOM-iMX7  Evaluation Kit Hardware Guide]] and [[SB-SOM: HOWTO: CAN Connection |  CAN node connection guide]].}}
{{:Transclusion: Debian: iMX7: CAN Bus}}

=== Touchscreen ===
See [[CL-SOM-iMX7:_Linux:_Kernel#Touchscreen_controllers_support|Touchscreen controllers support]] sections for kernel configuration details to enable support for the particular touchscreen.
The TI TSC2046 touchscreen driver is built-in the kernel if you use default CL-SOM-iMX7 configuration.

The X Windows system of CL-SOM-iMX7 uses tslib X server input driver to get the input from the touchscreen.

==== Touchscreen calibration ====
All supported touchscreen devices can be calibrated using {{cmd|xinput_calibrator}} utility.

To calibrate the touchscreen:
* Select the appropriate resolution for the touchscreen display in [[CL-SOM-iMX7:_U-Boot:_Display_and_console#Setting_the_.22displaytype.22_variable|U-Boot.]]
* Make sure the touchscreen driver is loaded as described in [[#Touchscreen|Touchscreen]] section
* Set the {{parameter|DISPLAY}} environment variable:
<pre> export DISPLAY=:0</pre>
* Start the X Server
<pre>
systemctl stop lightdm
startx&
</pre>
* Install ''xinput-calibrator'' deb package if not installed:
<pre>
root@cl-debian:~$ apt install xinput-calibrator
</pre>
* Run {{cmd|xinput_calibrator}} utility. For proper calibration you are required to touch the touchscreen corners and center in the following order: top-left, top-right, bottom-right, bottom-left, center.
* Create a file {{filename|/usr/share/X11/xorg.conf.d/99-calibration.conf}} and paste there a snippet with the calibration results:
<pre>
root@cl-rootfs:~# xinput_calibrator 
Calibrating standard Xorg driver "ADS7846 Touchscreen"
current calibration values: min_x=0, max_x=65535 and min_y=0, max_y=65535
If these values are estimated wrong, either supply it manually with the --precalib option, or run the 'get_precalib.sh' script to automatically get it (through HAL).
--> Making the calibration permanent <--
copy the snippet below into '/etc/X11/xorg.conf.d/99-calibration.conf' (/usr/share/X11/xorg.conf.d/ in some distro's)
Section "InputClass"
        Identifier          "calibration"
        MatchProduct  "ADS7846 Touchscreen"
        Option "MinX"  "2150"
        Option "MaxX"  "63262"
        Option "MinY"  "60654"
        Option "MaxY"  "2492"
        Option "SwapXY"    "0" # unless it was already set to 1
        Option "InvertX"   "0" # unless it was already set
        Option "InvertY"   "0" # unless it was already set
EndSection
</pre>
* For inverting X-axis (if required) add the following string to the {{filename|/usr/share/X11/xorg.conf.d/99-calibration.conf}}:
<pre>
        Option "TransformationMatrix"  "-1 0 1 0 1 0 0 0 1"
</pre>
* For inverting Y-axis (if required) add the following string to the {{filename|/usr/share/X11/xorg.conf.d/99-calibration.conf}}:
<pre>
        Option "TransformationMatrix"  "1 0 0 0 -1 1 0 0 1"
</pre>

=== MMC/SD ===
{{:Transclusion: Debian: CL-SOM-iMX7: MMC}}

=== GPIO access ===
{{:Transclusion: Debian: GPIO}}

=== Watchdog ===
{{:Transclusion: Debian: Watchdog}}

== See also ==

* [[CL-SOM-iMX7: Evaluation Kit: Getting Started]]
* [[CL-SOM-iMX7: Evaluation Kit: Hardware Guide]]
* [[CL-SOM-iMX7: Linux: Automatic Installation]]
* [[CL-SOM-iMX7: Linux: Manual Installation]]
* [[CL-SOM-iMX7: Linux: Kernel]]
* [[Linux: Development for ARM modules]]
* [[Linux: Debian: Minimal ARM filesystem]]
* [http://www.debian.org/doc/manuals/reference/index.en.html Debian Reference].

[[Category:Linux]]
[[Category:CL-SOM-iMX7]]