Configure a pi board

Configure a pi board to integrate a Raspberry Pi 4, Raspberry Pi 3 or Raspberry Pi Zero 2 W into your robot:

{
  "analogs": [
    {
      "chip_select": "<chip-select-pin-number-on-board>",
      "name": "<your-analog-reader-name>",
      "pin": "<pin-number-on-adc>",
      "spi_bus": "<your-spi-bus-name>",
      "average_over_ms": <int>,
      "samples_per_sec": <int>
    }
  ],
  "digital_interrupts": [
    {
      "name": "<your-digital-interrupt-name>",
      "pin": "<pin-number>",
      "type": "<basic|servo>"
    }
  ],
  "spis": [
    {
      "name": "<your-bus-name>",
      "bus_select": "<your-bus-index>"
    }
  ],
  "i2cs": [
    {
      "name": "<your-bus-name>",
      "bus": "<your-bus-index>"
    }
  ]
}

{
  "digital_interrupts": [
    {
      "name": "your-interrupt-1",
      "pin": "15"
    },
    {
      "name": "your-interrupt-2",
      "pin": "16"
    }
  ]
}

{
  "components": [
    {
      "name": "<your-pi-board-name>",
      "model": "pi",
      "type": "board",
      "namespace": "rdk",
      "attributes": {
        "analogs": [
          <...See table below...>
        ],
        "digital_interrupts": [
          <...See table below...>
        ],
        "spis": [
          <...See table below...>
        ],
        "i2cs": [
          <...See table below...>
        ]
      },
      "depends_on": []
    }
  ]
}

The following attributes are available for pi boards:

Attribute Configuration

Configuring these attributes on your board allows you to integrate analog-to-digital converters, digital interrupts, and components that must communicate through the SPI and I²C protocols into your robot.

analogs

An analog-to-digital converter (ADC) takes a continuous voltage input (analog signal) and converts it to an discrete integer output (digital signal).

ADCs are useful when building a robot, as they enable your board to read the analog signal output by most types of sensors and other hardware components.

To integrate an ADC into your robot, you must first physically connect the pins on your ADC to your board. If your ADC communicates with your board using SPI, you need to wire and configure the SPI bus in addition to the analogs.

Then, integrate analogs into the attributes of your board by adding the following to your board’s JSON configuration:

// "attributes": { ... ,
"analogs": [
  {
    "chip_select": "<chip-select-pin-number-on-board>",
    "name": "<your-analog-reader-name>",
    "pin": "<pin-number-on-adc>",
    "spi_bus": "<your-spi-bus-name>",
    "average_over_ms": <int>,
    "samples_per_sec": <int>
  }
]

{
  "components": [
    {
      "model": "pi",
      "name": "your-board",
      "type": "board",
      "attributes": {
        "analogs": [
          {
            "chip_select": "24",
            "name": "current",
            "pin": "1",
            "spi_bus": "main"
          },
          {
            "chip_select": "24",
            "name": "pressure",
            "pin": "0",
            "spi_bus": "main"
          }
        ],
        "spis": [
          {
            "bus_select": "0",
            "name": "main"
          }
        ]
      }
    }
  ]
}

The following properties are available for analogs:

digital_interrupts

Interrupts are a method of signaling precise state changes. Configuring digital interrupts to monitor GPIO pins on your board is useful when your application needs to know precisely when there is a change in GPIO value between high and low.

• When an interrupt configured on your board processes a change in the state of the GPIO pin it is configured to monitor, it calls Tick() to record the state change and notify any interested callbacks to “interrupt” the program.
• Calling Get() on a GPIO pin, which you can do without configuring interrupts, is useful when you want to know a pin’s value at specific points in your program, but is less precise and convenient than using an interrupt.

Integrate digital_interrupts into your robot in the attributes of your board by adding the following to your board’s JSON configuration:

// "attributes": { ... ,
"digital_interrupts": [
  {
    "name": "<your-digital-interrupt-name>",
    "pin": "<pin-number>",
  }
]

{
  "components": [
    {
      "model": "pi",
      "name": "your-board",
      "type": "board",
      "attributes": {
        "digital_interrupts": [
          {
            "name": "your-interrupt-1",
            "pin": "15"
          },
          {
            "name": "your-interrupt-2",
            "pin": "16"
          }
        ]
      }
    }
  ]
}

The following properties are available for digital_interrupts:

spis

Serial Peripheral Interface (SPI) is a serial communication protocol that uses four signal wires to exchange information between a controller and peripheral devices:

• Main Out/Secondary In: MOSI
• Main In/Secondary Out: MISO
• Clock, an oscillating signal line: SCLK
• Chip Select, with 1 line for each peripheral connected to controller: CS*

To connect your board (controller) and a component that requires SPI communication (peripheral device), wire a connection between CS and MOSI/MISO/SLCK pins on the board and component.

As supported boards have CS pins internally configured to correspond with SPI bus indices, you can enable this connection in your board’s configuration by specifying the index of the bus at your CS pin’s location and giving it a name.

Integrate spis into your robot in the attributes of your board by adding the following to your board’s JSON configuration:

// "attributes": { ... ,
"spis": [
  {
    "name": "<your-bus-name>",
    "bus_select": "<your-bus-index>"
  }
]

"spis": [
  {
    "name": "main",
    "bus_select": "0"
  }
]

The following properties are available for spis:

i2cs

The Inter-Integrated circuit (I²C) serial communication protocol is similar to SPI, but requires two signal wires to exchange information between a controller and a peripheral device:

• Serial Data: SDA
• Serial Clock: SCL

To connect your board (controller) and a component that requires I²C communication (peripheral device), wire a connection between SDA and SCL pins on the board and component.

As supported boards have SDA and SCL pins internally configured to correspond with I²C bus indices, you can enable this connection in your board’s configuration by specifying the index of the bus and giving it a name.

Integrate i2cs into your robot in the attributes of your board as follows:

// "attributes": { ... ,
{
  "i2cs": [
    {
      "name": "<your-bus-name>",
      "bus": "<your-bus-index>"
    }
  ]
}

// "attributes": { ... ,
{
  "i2cs": [
    {
      "name": "bus1",
      "bus": "1"
    }
  ]
}

The following properties are available for i2cs: