Configure an ADXL345 Accelerometer

The accel-adxl345 movement sensor model supports the Analog Devices ADXL345 digital accelerometer. This three axis accelerometer supplies linear acceleration data, supporting the LinearAcceleration method.

If you are using a Viam Rover, this is the accelerometer on it.

Navigate to the Config tab of your robot’s page in the Viam app. Click on the Components subtab and navigate to the Create component menu. Enter a name for your movement sensor, select the movement-sensor type, and select the accel-adxl345 model.

Click Create Component

Creation of an accel-adxl345 movement sensor in the Viam app config builder.

Edit and fill in the attributes as applicable.

{
  "components": [
    {
      "name": "<your-sensor-name>",
      "type": "movement_sensor",
      "model": "accel-adxl345",
      "attributes": {
        "board": "<your-board-name>",
        "i2c_bus": "<your-spi-bus-name-on-board>",
        "use_alternate_i2c_address": <boolean>,
        "tap": {
           "accelerometer_pin": <int>,
            "interrupt_pin": "<your-digital-interrupt-name-on-board>",
            "exclude_x": <boolean>,
            "exclude_y": <boolean>,
            "exclude_z": <boolean>,
            "threshold": <float>,
            "dur_us": <float>
        },
        "free_fall": {
            "accelerometer_pin": <int>,
            "interrupt_pin": "<your-digital-interrupt-name-on-board>",
            "threshold": <float>,
            "time_ms": <float>
        }
      },
      "depends_on": []
    }
  ]
}

{
  "components": [
    {
      "name": "local",
      "type": "board",
      "model": "pi",
      "attributes": {
        "i2cs": [
          {
            "name": "default_i2c_bus",
            "bus": "1"
          }
        ]
      }
    },
    {
      "name": "my-adxl",
      "type": "movement_sensor",
      "model": "accel-adxl345",
      "attributes": {
        "board": "local",
        "i2c_bus": "default_i2c_bus",
        "use_alternate_i2c_address": false
      }
    }
  ]
}

Attributes

NameTypeInclusionDescription
boardstringRequiredThe name of the board to which the device is wired.
i2c_busstringRequiredThe name of the I2C bus configured on the board wired to this device.
use_alt_i2c_addressboolOptionalDepends on whether you wire SDO low (leaving the default address of 0x53) or high (making the address 0x1D). If high, set true. If low, set false or omit the attribute.
Default: false
tapobjectOptionalHolds the configuration values necessary to use the tap detection interrupt on the ADXL345. See table below.
free_fallobjectOptionalHolds the configuration values necessary to use the free-fall detection interrupt on the ADXL345. See table below.

Tap attributes

Inside the tap object, you can include the following attributes:

NameTypeInclusionDescription
accelerometer_pinintRequiredOn the accelerometer you can choose to send the interrupts to int1 or int2. Specify this by setting this config value to 1 or 2.
interrupt_pinstringRequiredThe name of the digital interrupt you configured for the pin on the board wired to the accelerometer_pin.
exclude_xboolOptionalTap detection defaults to all three axes. Exclude the x axis by setting this to true.
Default: false
exclude_yboolOptionalTap detection defaults to all three axes. Exclude the y axis by setting this to true.
Default: false
exclude_zboolOptionalTap detection defaults to all three axes. Exclude the z axis by setting this to true.
Default: false
thresholdfloatOptionalThe magnitude of the threshold value for tap interrupt (in milligrams, between 0 and 15,937).
Default: 3000
dur_usfloatOptionalUnsigned time value representing maximum time that an event must be above the threshold to qualify as a tap event (in microseconds, between 0 and 159,375).
Default: 10000

Freefall attributes

Inside the freefall object, you can include the following attributes:

NameTypeInclusionDefault ValueDescription
accelerometer_pinintRequiredOn the accelerometer you can choose to send the interrupts to int1 or int2. Specify this by setting this config value to 1 or 2.
interrupt_pinstringRequiredThe name of the digital interrupt you configured for the pin on the board wired to the accelerometer_pin.
thresholdfloatOptionalThe acceleration on each axis is compared with this value to determine if a free-fall event occurred (in milligrams, between 0 and 15,937).
Default: 437.5
time_msfloatOptionalUnsigned time value representing the minimum time that the value of all axes must be less than threshold to generate a free-fall interrupt (in milliseconds, between 0 and 1,275).
Default: 160


Have questions, or want to meet other people working on robots? Join our Community Discord.