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Merge pull request #81 from chargebyte/everest/charge_som_trouble
Extend Troubleshooting & CAN documentation
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‎docs/source/hardware.rst‎

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.. _hardware.rst:
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########
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Hardware
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########
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###################
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Hardware Interfaces
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###################
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Since the Charge SOM itself is a module which cannot be used without a carrier board,
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the following sections refer to the Charge SOM Evaluation Board as an example.
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CAN (X16)
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*********
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The CAN-FD interface is connected to X16, which is a full implementation of the CAN FD
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protocol specification version 2.0B. It is available on Linux network interface ``can0``.
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The CAN-FD interface is connected to X16, which is a full implementation of the CAN FD protocol
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specification version 2.0B. It is available on Linux network interface ``can0``, which has a
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default bitrate of 1 Mbit/s.
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CAN Configuration
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=================
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In order to change the default CAN bitrate of can0 interface, please adapt ``BitRate`` value and
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run the following commands:
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.. code-block:: console
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mkdir /etc/systemd/network/can0.network.d
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cat <<EOF > /etc/systemd/network/can0.network.d/bitrate.conf
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[CAN]
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BitRate=125000
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EOF
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networkctl reload
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networkctl reconfigure can0
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systemctl restart everest
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The change takes effect immediately, but also persists across reboots and
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firmware updates.
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********************************************
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Insulation Monitoring Device (IMD, X9 + X15)
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+---------------+------------------+-----------------------------------+-------------------------------------------+
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| SDIO | 1 | | |
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+---------------+------------------+-----------------------------------+-------------------------------------------+
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| CAN | 1 | | |
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| CAN [#]_ | 1 | | |
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+---------------+------------------+-----------------------------------+-------------------------------------------+
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| PWM | 6 | | |
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+---------------+------------------+-----------------------------------+-------------------------------------------+
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| GPIO | 16 | - imx93-charge-som-clko-gpio.dtso | Warning: short clock after power-up/reset |
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+---------------+------------------+-----------------------------------+-------------------------------------------+
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.. [#] The UART7 has RTS/CTS signals available.
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.. [#] Keep in mind that these signals must be connected to a CAN transceiver.
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The following table indicates all possible muxing options for these signals.
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By default, the factory shipped configuration for the Charge SOM EVB is that the signals GPIO3_26 and GPIO3_27

‎docs/source/troubleshooting.rst‎

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which uses the CAN interface. This might help as a starting point.
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How can I access the GPIOs under Linux?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Since the GPIO sysfs interface /sys/class/gpio has been deprecated since Linux 4.8,
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we recommend the usage of chardev GPIO and libgpiod. The modification of the bias
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settings via libgpiod is not yet implemented, so it needs to be done via device tree.
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What is the difference between CHSTOP_IN and SAFETY_ESTOPx?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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In order to realize realtime emergency stop behavior use the SAFETY_ESTOPx signals, which are connected to the safety processor.
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Is there a Linux command to check for connection related CAN issues?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Yes
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.. code-block:: console
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root@chargesom:/# ip -details -statistic link show can0
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How can I list the available UARTs?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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All UARTs of the i.MX93 are handled by the fsl-lpuart driver, so the following
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command should list all available UARTs. Please keep in mind that Linux starts
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counting from zero (ttyLP0 = UART1, ...).
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.. code-block:: console
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root@chargesom:/# cat /proc/tty/driver/fsl-lpuart
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serinfo:1.0 driver revision:
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0: uart:FSL_LPUART mmio:0x44380010 irq:17 tx:9932 rx:0 RTS|CTS|DTR|DSR|CD
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2: uart:FSL_LPUART mmio:0x42570010 irq:18 tx:12966 rx:26572 RTS|CTS|DTR|DSR|CD
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3: uart:FSL_LPUART mmio:0x42580010 irq:19 tx:936 rx:617 RTS|CTS|DTR|DSR|CD
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4: uart:FSL_LPUART mmio:0x42590010 irq:20 tx:0 rx:0 CTS|DSR|CD
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How can I print the current pin/pad control settings (e.g. bias, drive strength)?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The current PAD control settings are available under Linux only via debugfs,
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but this requires an equivalent pinctrl setting within the device tree:
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.. code-block:: console
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root@chargesom:/# cat /sys/kernel/debug/pinctrl/443c0000.pinctrl/pinconf-pins
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Pin config settings per pin
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Format: pin (name): configs
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pin 0 (IMX93_IOMUXC_DAP_TDI): 0x31e
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...
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Which LVDS displays have been tested with the Charge SOM EVB?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The `Distec DD-0700-MC01 <https://www.fortec-integrated.de/en/products/tft-components/tft-displays/detail/fortec-integrated/dd-0700-mc01/>`_
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(7 inch, 800x480 resolution) has been tested with the Charge SOM EVB.
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I like to create my own DT overlay. Is there an example?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Yes, please have a look at this `commit <https://github.com/chargebyte/linux/commit/125a587a0cf7e8d9db1fdddf9383a67c2b46d107>`_ .
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Where can I find the device tree sources of the Charge SOM?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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