Configure a Custom Linux Board

The customlinux board model supports boards like the Mediatek Genio 500 Pumpkin that run Linux operating systems and are not supported by other built-in Viam models.

To integrate a custom Linux board into your machine:

1. Install viam-server on your machine.
2. Create a board definitions file, specifying the mapping between your board’s GPIO pins and connected hardware.
3. Configure a customlinux board on your machine, specifying the path to the definitions file in the board configuration.

Install viam-server

viam-server is distributed for Linux as an AppImage. The AppImage is a single, self-contained binary that runs on 64-bit Linux systems running the aarch64 or x86_64 architectures, with no need to install any dependencies.

To install viam-server :

1. Go to the Viam app and add a new machine by providing a name in the New machine field and clicking Add machine. If this is your first time using the Viam app, you must create an account first.

   

2. Navigate to the CONFIGURE tab and find your machine’s card. An alert will be present directing you to Set up your machine part. Click View setup instructions to open the setup instructions. Select Linux as your system’s OS, Aarch64 as your Linux architecture, and RDK as the RDK type.

3. Follow the instructions listed to install viam-server on your Linux computer.

4. Once you have followed the setup instructions, viam-server is installed and running. Wait for confirmation that your computer has successfully connected.

By default, viam-server will start automatically when your system boots, but you can change this behavior if desired.

Create a board definitions file

The board definitions file describes the location of each GPIO pin on the board so that viam-server can access the pins correctly.

On your customlinux board, create a JSON file in the directory of your choice with and provide the mappings between your GPIO pins and connected hardware. Use the template and example below to populate the JSON file with a single key, "pins", whose value is a list of objects that each represent a pin on the board.

{
  "pins": [
    {
      "name": "<pin-name>",
      "device_name": "<gpio-device-name>",
      "line_number": <integer>,
      "pwm_chip_sysfs_dir": "<pwm-device-name>"
      "pwm_id": <integer>
    },
    ...
  ]
}

{
  "pins": [
    {
      "name": "3",
      "device_name": "gpiochip0",
      "line_number": 81,
      "pwm_id": -1
    },
    {
      "name": "5",
      "device_name": "gpiochip0",
      "line_number": 84,
      "pwm_id": -1
    },
    {
      "name": "7",
      "device_name": "gpiochip0",
      "line_number": 150,
      "pwm_id": -1
    },
    {
      "name": "11",
      "device_name": "gpiochip0",
      "line_number": 173,
      "pwm_id": -1
    },
    {
      "name": "13",
      "device_name": "gpiochip0",
      "line_number": 152,
      "pwm_id": -1
    },
    {
      "name": "15",
      "device_name": "gpiochip0",
      "line_number": 94,
      "pwm_id": -1
    },
    {
      "name": "19",
      "device_name": "gpiochip0",
      "line_number": 163,
      "pwm_id": -1
    },
    {
      "name": "21",
      "device_name": "gpiochip0",
      "line_number": 161,
      "pwm_id": -1
    },
    {
      "name": "23",
      "device_name": "gpiochip0",
      "line_number": 164,
      "pwm_id": -1
    },
    {
      "name": "27",
      "device_name": "gpiochip0",
      "line_number": 82,
      "pwm_id": -1
    },
    {
      "name": "29",
      "device_name": "gpiochip0",
      "line_number": 98,
      "pwm_id": -1
    },
    {
      "name": "31",
      "device_name": "gpiochip0",
      "line_number": 12,
      "pwm_id": -1
    },
    {
      "name": "33",
      "device_name": "gpiochip0",
      "line_number": 101,
      "pwm_id": -1
    },
    {
      "name": "35",
      "device_name": "gpiochip0",
      "line_number": 171,
      "pwm_id": -1
    },
    {
      "name": "37",
      "device_name": "gpiochip0",
      "line_number": 169,
      "pwm_id": -1
    },
    {
      "name": "8",
      "device_name": "gpiochip0",
      "line_number": 115,
      "pwm_id": -1
    },
    {
      "name": "10",
      "device_name": "gpiochip0",
      "line_number": 121,
      "pwm_id": -1
    },
    {
      "name": "12",
      "device_name": "gpiochip0",
      "line_number": 170,
      "pwm_id": -1
    },
    {
      "name": "16",
      "device_name": "gpiochip0",
      "line_number": 165,
      "pwm_id": -1
    },
    {
      "name": "18",
      "device_name": "gpiochip0",
      "line_number": 1,
      "pwm_id": -1
    },
    {
      "name": "22",
      "device_name": "gpiochip0",
      "line_number": 2,
      "pwm_id": -1
    },
    {
      "name": "24",
      "device_name": "gpiochip0",
      "line_number": 162,
      "pwm_id": -1
    },
    {
      "name": "26",
      "device_name": "gpiochip0",
      "line_number": 0,
      "pwm_id": -1
    },
    {
      "name": "28",
      "device_name": "gpiochip0",
      "line_number": 83,
      "pwm_id": -1
    },
    {
      "name": "32",
      "device_name": "gpiochip0",
      "line_number": 97,
      "pwm_id": -1
    },
    {
      "name": "36",
      "device_name": "gpiochip0",
      "line_number": 151,
      "pwm_id": -1
    },
    {
      "name": "38",
      "device_name": "gpiochip0",
      "line_number": 174,
      "pwm_id": -1
    },
    {
      "name": "40",
      "device_name": "gpiochip0",
      "line_number": 172,
      "pwm_id": -1
    }
  ]
}

The following parameters are available for each pin object:

Tips for finding GPIO information

To see which chips exist and how many lines each chip has, run this command on your board:

sudo gpiodetect

Here is example output from this command on an Odroid C4:

gpiochip0 [aobus-banks] (16 lines)
gpiochip1 [periphs-banks] (86 lines)

This example output indicates that there are two GPIO chips on this board. One has 16 lines, numbered 0-15. The other has 86 lines, numbered 0-85.

To see info about every line on every GPIO chip, run this command:

sudo gpioinfo

Here is example output from the sudo gpioinfo command on an Odroid C4:

...
  line  62:      unnamed       unused   input  active-high
  line  63:      unnamed       unused   input  active-high
  line  64:     "PIN_27"       unused   input  active-high
  line  65:     "PIN_28"       unused   input  active-high
  line  66:     "PIN_16"       unused   input  active-high
  line  67:     "PIN_18"       unused   input  active-high
  line  68:     "PIN_22"       unused   input  active-high
...

In this example, the human-readable names such as "PIN_28" indicate which physical board pin each line is attached to. However, these names are not standardized. Some boards have pin names like "PH.03". In either case, you need to look at the data sheet for your board and determine how the pin names map to the hardware.

Tips for finding PWM information

Run the following command and look for unique strings within each symlink.

ls -l /sys/class/pwm

Here is example output from this command on a Jetson Orin AGX:

total 0
lrwxrwxrwx 1 root root 0 Sep  8  2022 pwmchip0 -> ../../devices/3280000.pwm/pwm/pwmchip0
lrwxrwxrwx 1 root root 0 Sep  8  2022 pwmchip1 -> ../../devices/32a0000.pwm/pwm/pwmchip1
lrwxrwxrwx 1 root root 0 Sep  8  2022 pwmchip2 -> ../../devices/32c0000.pwm/pwm/pwmchip2
lrwxrwxrwx 1 root root 0 Sep  8  2022 pwmchip3 -> ../../devices/32f0000.pwm/pwm/pwmchip3
lrwxrwxrwx 1 root root 0 Sep  8  2022 pwmchip4 -> ../../devices/39c0000.tachometer/pwm/pwmchip4

Based on this example output, the values to use for pwm_chip_sysfs_dir are 328000.pwm, 32a0000.pwm, and so on.

Each of these directories contains a file named npwm containing a number. The number in each file is the number of lines on the chip. The pwm_id value will be between 0 and one less than the number of lines. For example, if the npwm contains "4", then the valid pwm_id values are 0, 1, 2, and 3.

Determining which specific chip and line are attached to each pin depends on the board. Try looking at your board’s data sheet and cross-referencing with the output from the commands above.

Configure your board

{
  "components": [
    {
      "name": "<your-customlinux-board>",
      "model": "customlinux",
      "type": "board",
      "namespace": "rdk",
      "attributes": {
        "board_defs_file_path": "<file_path>"
      },
      "depends_on": []
    }
  ]
}

{
  "components": [
    {
      "name": "myCustomBoard",
      "model": "customlinux",
      "type": "board",
      "namespace": "rdk",
      "attributes": {
        "board_defs_file_path": "/home/root/board.json"
      },
      "depends_on": []
    }
  ]
}

The following attributes are available for customlinux boards: