Use the BeagleBone Black ADC to Capture Analog Data

This example shows how to use the BeagleBone Black ADC to perform a simple voltage measurement using a potentiometer.

The BeagleBone Black hardware has six analog-to-digital converter (ADC) modules associated with six analog input pins. You can use these pins to measure positive voltages in the range 0 V (GND_ADC) - 1.8 V (VDD_ADC).

In addition to your BeagleBone Black board and USB cable, you must have the following equipment:

  • 1 10 kΩ potentiometer

  • Breadboard and jumper cables

The potentiometer (POT) is a three-terminal device with terminals 1 and 3 comprising the end points of a resistor embedded in the POT. The second terminal is connected to a variable wiper. As the wiper moves, the resistance values across terminals 1 and 2 and terminals 2 and 3 change. In this circuit, POT acts as a variable voltage divider. As you move the knob of the potentiometer, the voltage seen at terminal 2 changes between 1.8 V (VDD_ADC) and 0 V (GND_ADC).

Caution

  • Never connect a voltage greater than 1.8 Vacross the ADC pins. Voltages greater than 1.8 V can damage the board.

  • Always connect the negative (ground) side of a voltage source to GND_ADC. The ADC measures positive voltages only. A reversed connection can damage the board.

  1. Configure the BeagleBone Black hardware.

    • Insert a black probe lead into the GND_ADC socket (P8_34).

    • Insert a white probe lead into the VDD_ADC socket (P8_32).

    • Insert a red probe lead into the AIN0 socket (P8_39)

    • Connect the white lead to terminal 1 of the POT. Connect the black lead to terminal 3 of the POT. Connect the red lead to terminal 2 of the POT.

  2. Start MATLAB®.

  3. Connect the BeagleBone Black board to a host computer USB port and wait about 30 seconds for the board to start.

  4. Connect the BeagleBone Black driver interface to the board.

    bbb = beaglebone
    bbb = 
    
      beaglebone with properties:
    
               DeviceAddress: '192.168.7.2'
                   BoardName: 'BeagleBone Black Rev 00C0'
               AvailableLEDs: {'USR0'  'USR1'  'USR2'  'USR3'}
        AvailableDigitalPins: {1x29 cell}
         AvailableAnalogPins: {'AIN0'  'AIN1'  'AIN2'  'AIN3'  'AIN4'  'AIN5'  'AIN6'}
            AvailablePWMPins: {}
        AvailableSPIChannels: {}
           AvailableI2CBuses: {'i2c-1'}
        AvailableSerialPorts: {}
            AvailableWebcams: {} 
  5. Verify that 'AIN0' is an available analog pin.

    bbb.AvailableAnalogPins
    ans = 
    
        'AIN0'    'AIN1'    'AIN2'    'AIN3'    'AIN4'    'AIN5'    'AIN6'
  6. Set the POT to its lowest position. Read the voltage.

    v_AA = readVoltage(bbb, 'AIN0')
    vv_AA =
    
        1.8
  7. Set the POT to its highest position. Read the voltage.

    v_AA = readVoltage(bbb, 'AIN0')
    vv_AA =
    
        0.0