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How to use GPIOs on CC6UL and CC6

GPIOs can be accessed from Linux user space through the sysfs interface, example:

echo 4 >/sys/class/gpio/export
echo out >/sys/class/gpio/gpio4/direction
echo 1 >/sys/class/gpio/gpio4/value
echo 0 >/sys/class/gpio/gpio4/value

Digi Embedded Yocto offers an example application gpio_sysfs_test which can be added to local.conf:

EXTRA_IMAGE_FEATURES += dey-examples

IMAGE_INSTALL_append += dey-examples-gpio-sysfs

 

Usage: gpio-sysfs-test <gpio_in> [gpio_out]

 Where gpio_in is a pushbutton and gpio_out an optional LED

Sources:

<dey-install-folder>/sources/meta-digi/meta-digi-dey/recipes-digi/dey-examples/files/gpio_sysfs_test/gpio_sysfs_test.c.

When using GPIOS from the MCA the base address is gpiochip504.

When using GPIOs on the CC6UL development board i/o-expander, make sure you have firmware loaded for the i/o expander:

# sysinfo

..

|| I/O Expander | HW_VERSION=1  FW_VERSION=0.2

..

if it shows FW_VERSION=?? or you don't have sysinfo and can't access:

cat /sys/bus/i2c/devices/0-006e/fw_version

check: i/o expander not programmedi/o expander not programmed


The base address for the i/o expander is gpiochip465. See:

https://www.digi.com/resources/documentation/digidocs/90001547/#reference/bsp/v4-1_6ul/r_io_expander_gpio.htm

The User LED on the CC6UL SBC is connected to IO23 of the i/o expander, its gpio number is 488 (465 + 23), example:

echo 488 >/sys/class/gpio/export
echo out >/sys/class/gpio/gpio488/direction

cat  /sys/class/gpio/gpio488/value

0
echo 1 >/sys/class/gpio/gpio488/value
echo 0 >/sys/class/gpio/gpio488/value

References:

https://www.digi.com/resources/documentation/digidocs/90001547/#reference/bsp/v4-1_6ul/r_gpio_6ul.htm

https://github.com/digi-embedded/linux/blob/v4.1/dey-2.2/maint/Documentation/gpio/sysfs.txt

https://github.com/digi-embedded/linux/blob/v4.1/dey-2.2/maint/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt

Last updated: Oct 06, 2017

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