Improve CAN documentation

Signed-off-by: Stefan Wahren <stefan.wahren@chargebyte.com>

Author: lategoodbye

docs/source/hardware.rst

@@ -1,8 +1,8 @@
 .. _hardware.rst:
 
-########
-Hardware
-########
+###################
+Hardware interfaces
+###################
 
 Since the Charge SOM itself is a module which cannot be used without a carrier board,
 the following sections refer to the Charge SOM Evaluation Board as an example.
@@ -86,8 +86,33 @@ the board supports up to two EIA-485 interfaces.
 CAN (X16)
 *********
 
-The CAN-FD interface is connected to X16, which is a full implementation of the CAN FD
-protocol specification version 2.0B. It is available on Linux network interface ``can0``.
+The CAN-FD interface is connected to X16, which is a full implementation of the CAN FD protocol
+specification version 2.0B. It is available on Linux network interface ``can0``, which has a
+default bitrate of 1 Mbit/s.
+
+CAN configuration
+=================
+
+In order to change the default CAN bitrate permanent, please adapt BitRate value and run the following commands:
+
+.. code-block:: console
+
+   cat <<EOF > /etc/systemd/network/can0.network
+   [Match]
+   Name=can0
+
+   [Link]
+   RequiredForOnline=no
+
+   [CAN]
+   BitRate=125000
+   TripleSampling=yes
+   EOF
+
+   networkctl reload
+   networkctl reconfigure can0
+   systemctl restart everest
+
 
 ********************************************
 Insulation Monitoring Device (IMD, X9 + X15)
@@ -135,14 +160,15 @@ still depend on the pinmuxing of these 16 pins!
 +---------------+------------------+-----------------------------------+-------------------------------------------+
 | SDIO          | 1                |                                   |                                           |
 +---------------+------------------+-----------------------------------+-------------------------------------------+
-| CAN           | 1                |                                   |                                           |
+| CAN [#]_      | 1                |                                   |                                           |
 +---------------+------------------+-----------------------------------+-------------------------------------------+
 | PWM           | 6                |                                   |                                           |
 +---------------+------------------+-----------------------------------+-------------------------------------------+
 | GPIO          | 16               | - imx93-charge-som-clko-gpio.dtso | Warning: short clock after power-up/reset |
 +---------------+------------------+-----------------------------------+-------------------------------------------+
 
 .. [#] The UART7 has RTS/CTS signals available.
+.. [#] Keep in mind that these signals must be connected to a CAN transceiver.
 
 The following table indicates all possible muxing options for these signals.
 By default, the factory shipped configuration for the Charge SOM EVB is that the signals GPIO3_26 and GPIO3_27

docs/source/troubleshooting.rst

@@ -58,6 +58,16 @@ for timing critical use cases. Currently there is no EVerest module, which is ab
 In order to realize realtime emergency stop behavior use the SAFETY_ESTOPx signals, which are connected to the safety processor.
 
 
+Is there a Linux command to check for connection related CAN issues?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Yes
+
+.. code-block:: console
+
+   root@chargesom:/# ip -details -statistic link show can0
+
+
 How can I list the available UARTs?
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^