Dave Embedded Systems SBC AXEL, Руководство пользователя

Страница: 56 / 139

S B C X U s e r ' s G u i d e v . 1 . 0 . 1
gadget: high-speed config #1: Linux File-Backed Storage
5.13 GPIOs
i.MX6 can handle external pins in many different ways and most of them
can be configured as GPIOs. When a pin is set as a GPIO, it is possible
to read its value, change its direction or change output value directly from
the shell. The GPIOs can be easily accessed from sysfs: in the
/sys/class/gpio/ folder there are sub-folders, one for each
manageableGPIO. Each sub-folder contains files that indicate:
●
direction (in / out)
◾ The direction indicates wheter the PIN is listening, in, or ready to
send an output.
● Value (0 / 1)
◾ The value, is just like a state. Where 0 means low, and 1 means high.
For further details about how to manage the GPIOs from sysfs, please
refer to the Linux kernel documentation at Documentation/gpio.txt.
5.13.1 Available GPIOs
The following table reports the signals available as GPIOs by default:
Connector.PIN Pin Name GPIO number Sysfs mapping
J33.28 EIM_D26 GPIO3_IO26 gpio90
J33.30 EIM_D27 GPIO3_IO27 gpio91
J33.32 GPIO_17 GPIO7_IO12 gpio204
J33.34 GPIO_6/
I2C3_SDA GPIO1_IO06 gpio6
5.13.2 Accessing the peripheral
If not already exported, the GPIO must be added to the list of exported
GPIOs:
echo XX > /sys/class/gpio/export
To read a GPIO direction:
cat /sys/class/gpio/gpioXX/direction
In or Out output is now expected To change the pin direction:
echo out > /sys/class/gpio/gpioXX/direction
or
December, 2019
56/139