How To Access GPIO

This guide will teach you how to access the GPIO using Android and Ubuntu.

GPIO Number List

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PIN         GPIO        Number
PIN15       GPIO1_C2     50
PIN16       GPIO1_C1     49
PIN22       GPIO1_C0     48
PIN23       GPIO1_B7     47
Tip

Some GPIOs may be set to other functions by default, e.g. I2C. If you want to use them as GPIO you need to modify the DTS.

How To Get GPIO Number

You can use the following formula to get GPIO number:

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n = (block_number * 32) + (sub_block_number * 8) + index

Where:

  • block_number: index of the block number
  • sub_block_number: the alphabetical index of the block name, minus 1
  • index: the pin number within the block

Example: PIN15(GPIO1_C2)

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GPIO1_C2 -> (1 * 32) + (2 * 8) + 2 = 50

How To Access GPIO Via Terminal

Request the gpio(GPIO1_C2)

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$ echo 50 > /sys/class/gpio/export

Config the gpio(GPIO1_C2) as output

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$ echo out > /sys/class/gpio/gpio50/direction

Config the gpio(GPIO1_C2) as high level output

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$ echo 1 >  /sys/class/gpio/gpio50/value

Config the gpio(GPIO1_C2) as low level output

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$ echo 0 >  /sys/class/gpio/gpio50/value

Config the gpio(GPIO1_C2) as input

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$ echo in > /sys/class/gpio/gpio50/direction

Get the level of gpio(GPIO1_C2)

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$ cat  /sys/class/gpio/gpio50/value

Release the gpio(GPIO1_C2)

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$ echo 50 > /sys/class/gpio/unexport