Linux/TMDXEVM3358: GPIO read example

Karol Duzinkiewicz

Part Number: TMDXEVM3358

Tool/software: Linux

Hi All,

I'm new to embedded Linux and Processor SDK Linux development so I wanted to ramp up my knwoledge with some basic program. Let's say I would like to use one of the pins on the EVM's EXT1 connector as input and inside my code I would like to read the logical state of this pin and print it out using the stdout. This is trivial on HW like Arduino, but I just can't figure out how I should do it on the EVM?

I'm going through the traininigs, wikis and documentation but I just can't find some hands-on example of this type of source code.

I would appreciate any type of help.

Regards,

Karol

over 7 years ago

0 Cvetolin Shulev-XID over 7 years ago

TI__Guru 65405 points

Hi Karol,

Are you trying to read the GPIO value in Kernel or in user space?
Did you read the Linux PSP GPIO Driver guide at:
processors.wiki.ti.com/.../Linux_PSP_GPIO_Driver_Guide

BR
Tsvetolin Shulev

0 Karol Duzinkiewicz over 7 years ago in reply to Cvetolin Shulev-XID

Intellectual 365 points

Hi Tsvetolin,
ideally I wouldn't like to touch the kernel space & read the GPIO value inside the user space application. Is that possible?

Regards,

Karol

0 Cvetolin Shulev-XID over 7 years ago in reply to Karol Duzinkiewicz

TI__Guru 65405 points

Karol,

The linked in my previous post GPIO guide gives you basic experience about read/write GPIO in user space by sysfs control.
The steps are as follow (using GPIO 30 for example):
$ echo 30 > /sys/class/gpio/export
$ echo "in" > /sys/class/gpio/gpio30/direction
then you can reading the GPIO value by:
cat /sys/class/gpio/gpio30/value

Also there is more advanced approach for read/write a GPIO in user space. You can make a memory map to access memory mapped devices (GPIO address space for example). See examples below:
elinux.org/EBC_Exercise_11b_gpio_via_mmap
stackoverflow.com/.../driving-beaglebone-gpio-through-dev-mem
github.com/.../gpio.c
blogdugas.net/.../

BR
Tsvetolin Shulev

0 Karol Duzinkiewicz over 7 years ago in reply to Cvetolin Shulev-XID

Intellectual 365 points

Thanks a lot Tsvetolin!!!

Regards,

Karol

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Linux/TMDXEVM3358: GPIO read example