Use the BeagleBone Black PWM to Capture PWM Measurements

This example shows how to use the BeagleBone Black PWM to generate a square wave of given frequency and duty cycle.

The BeagleBone Black board has eight pulse-width modulation (PWM) output pins. Each PWM pin outputs a square waveform with variable frequency and duty cycle.

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

  • LED

  • 1 kΩ resistor

  • Breadboard and jumper cables

You will configure a GPIO pin (P9_14) as a PWM pin (PWM1A).

  1. Configure the BeagleBone Black hardware.

    • Using a white cable, connect P9_14 (PWM1A) to the 1 kΩ resistor.

    • Using a white cable, connect the 1 kΩ resistor to the LED input.

    • Using a black cable, connect the LED output to P9_01 (DGND).

  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: ''
                   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. Enable pin P9_14 as a PWM pin.

    enablePWM(bbb, 'P4_14')
    ans = 
  6. Set the frequency to 1000 Hz and the voltage to 1.5 V.

  7. Loop the duty cycle from 0.0 to 1.0 and back again, pausing between increments. Observe the resulting behavior.

    for dc = 0.0 : 0.1 : 1.0
    for dc = 1.0 : -0.1  :0.0

When you are finished using the PWM, restart the hardware to make additional GPIO pins available.