How to Control BeagleBone's GPIOs

Following is a handy reference that you can use to control and access your BeagleBone’s general purpose input/output (GPIOs) with the file system, BoneScript, and Python.

Controlling the GPIO with the file system

You can use the following commands to control the GPIO with the file system.

• Exporting a pin:

  echo 40 > /sys/class/gpio/export

• Setting a pin OUTPUT:

  echo out > /sys/class/gpio/gpio40/direction

• Writing a pin HIGH:

  echo 1 > /sys/class/gpio/gpio40/value

• Writing a pin LOW:

  echo 0 > /sys/class/gpio/gpio40/value

• Setting a pin INPUT:

  echo in > /sys/class/gpio/gpio40/direction

• Reading the value from an INPUT pin (returns 1 for HIGH and 0 for LOW):

• cat /sys/class/gpio/gpio40/value

Controlling the GPIO with BoneScript

You can use the following BoneScript commands to control the GPIO.

• Loading a BoneScript module:

  var b = require('bonescript');

• Setting a pin OUTPUT:

  b.pinMode("P9_14", b.OUTPUT);

• Writing a pin HIGH:

  b.digitalWrite("P9_14", b.HIGH);

• Writing a pin LOW:

  b.digitalWrite("P9_14", b.LOW);

• Setting a pin INPUT:

  b.pinMode("P8_11", b.INPUT);

• Reading the value from a digital INPUT pin (returns HIGH or LOW):

  b.digitalRead("P8_11");

• Setting a pin for pulse-width modulation (PWM) with 50 percent duty cycle:

  b.pinMode('P9_14', b.OUTPUT);
  b.analogWrite('P9_14', 0.5);

• Reading the value from an analog INPUT pin (returns a value between 0 and 1):

• b.analogRead('P9_40');

Controlling the GPIO with Python

You can use the following Python commands to control the GPIO.

• Importing Adafruit’s BeagleBone Input Output Library:

  import Adafruit_BBIO.GPIO as GPIO

• Setting a pin OUTPUT:

  GPIO.setup("P9_14", GPIO.OUT)

• Writing a pin HIGH:

  GPIO.output("P9_14", GPIO.HIGH)

• Writing a pin LOW:

  GPIO.output("P9_14", GPIO.LOW)

• Setting a pin INPUT:

  GPIO.setup("P8_11", GPIO.IN)

• Reading the value from a digital INPUT pin (returns HIGH or LOW):

  GPIO.input("P8_11")

• Setting a pin for PWM with 50 percent duty cycle:

  import Adafruit_BBIO.PWM as PWM
  PWM.start("P9_14", 50)

• Setting an analog INPUT:

  import Adafruit_BBIO.ADC as ADC
  ADC.setup()

• Reading the value from an analog INPUT pin (returns a value between 0 and 1):

• analogReading = ADC.read("P9_40")