GPIO pin access, R-Car H3

Hello Shyubham-san

I hope the following helps you.

How to access GPIO via sysfs

Ex) Case of : H3 starter Kit, GP5-17(SW2-1)

1) Build with "CONFIG_GPIO_SYSFS" enabled in the kernel and boot

              Device Drivers ->

                            SGPIO Support ->

                                          [*] /sys/class/gpio/... (sysfs intercase)

2) Access to GPIO via sysfs

The pin's sysfs GPIO index:

              # cat /sys/kernel/debug/gpio

This should list all GPIO pins available in the system along with their status.

For example, the following should be listed for GP5:

             gpiochip5: GPIOs 392-417, parent: platform/e6055000.gpio, e6055000.gpio:

               gpio-393 (                    |SDHI0 VccQ          ) out hi

               gpio-394 (                    |regulator-vcc-sdhi0 ) out lo

The first line gives you the following information: GP5_0 sysfs index is 392.

If you want to read GP5_17 (SW2-1) you have to use sysfs index 409 (392 + 17 = 409).

Since gpio-409 is not listed above, it's unused, and you can grab it as follows:

               # echo 409 > /sys/class/gpio/export

 The following directory should appear under /sys/class/gpio:

               # ls /sys/class/gpio/gpio409/

              active_low  device  direction  edge  power  subsystem  uevent  value

 These are the GPIO pin control files. By default, the GPIO is configured an active high input:

               # cat /sys/class/gpio/gpio409/active_low

              0

              # cat /sys/class/gpio/gpio409/direction

              in

 The following command reads the GPIO pin state:

               # cat /sys/class/gpio/gpio409/value

              1

 If you toggle SW2.1, the following value should be read:

               # cat /sys/class/gpio/gpio409/value

              0

The following command sets GPIO active low:

               # echo 1 > /sys/class/gpio/gpio409/active_low

Similarly, the GPIO direction can be changed by writing "out" to the "/sys/class/gpio/gpio<N>/direction" file; although, it's not safe to set output direction for input pins.

For more information, please refer to the following

www.kernel.org/.../sysfs.txt

Hello Shyubham,

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Hello Shyubham,

This question has been opened but there is no reply for a long time.
We have a tentative answer already, so I will close this question.
If you have any updates or want to ask another question, please post new question.