Trucrux Inc

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To get state of GPIO run the following command

root@imx8mq-trux-q01:~# cat /sys/kernel/debug/gpio

Output :

gpiochip0: GPIOs 0-31, parent: platform/30200000.gpio, 30200000.gpio:
gpio-5 ( |hdmi_on ) out lo 
gpio-8 ( |eth_phy ) out hi 
gpio-10 ( |int ) in hi IRQ 
gpio-12 ( |spi_imx ) out hi

gpiochip1: GPIOs 32-63, parent: platform/30210000.gpio, 30210000.gpio:
gpio-44 ( |cd ) in lo IRQ ACTIVE LOW
gpio-51 ( |regulator-vsd-3v3 ) out hi 
gpio-52 ( |spi_imx ) out hi

gpiochip2: GPIOs 64-95, parent: platform/30220000.gpio, 30220000.gpio:

gpiochip3: GPIOs 96-127, parent: platform/30230000.gpio, 30230000.gpio:
gpio-102 ( |Back ) in lo IRQ ACTIVE LOW
gpio-109 ( |Home ) in lo IRQ ACTIVE LOW
gpio-111 ( |Down ) in lo IRQ ACTIVE LOW
gpio-113 ( |eMMC ) out lo 
gpio-114 ( |Up ) in lo IRQ ACTIVE LOW

gpiochip4: GPIOs 128-159, parent: platform/30240000.gpio, 30240000.gpio:
gpio-137 ( |spi_imx ) in lo 
gpio-142 ( |scl ) out hi 
gpio-143 ( |sda ) in hi 
gpio-144 ( |scl ) out hi 
gpio-145 ( |sda ) in hi 
gpio-146 ( |scl ) out hi 
gpio-147 ( |sda ) in hi 
gpio-148 ( |scl ) out hi 
gpio-149 ( |sda ) in hi

Each GPIO is defined as “in” or “out” and the state is shown as “lo” or “hi”. This can be changed via ‘sys/class/gpio’

1. Export GPIO

echo <GPIO_NUMBER> > /sys/class/gpio/export

2. Configure GPIO

echo <in or out> > /sys/class/gpio<gpionumber>/direction

3. Changing value of GPIO

echo <1 or 0> > /sys/class/gpio<gpionumber>/value

4. Read Gpio

  • direction
cat /sys/class/gpio<gpionumber>/direction
  • value
cat /sys/class/gpio<gpionumber>/value

5. Unexport gpio after use

echo <GPIO_NUMBER> > /sys/class/gpio/unexport