The operation of GPIO is the most basic operation in embedded devices. The general approach is to write a separate driver, which is the case in most examples on the Internet. In fact, there is a universal GPIO operation interface under Linux, which is the "/sys/class/gpio" method I will introduce.
First, check if there is a folder called "/sys/class/gpio" in the system. If not, add it to Device Drivers —> GPIO Support —> /sys/class/gpio/… (sysfs interface) when compiling the kernel.
Instructions for using /sys/class/gpio:
| 01 | gpio_operation operates the IO port GPIO to the file system mapping through the /sys/ file interface |
class/gpio
The class/gpio/export file is used to inform the system of the GPIO pin number that needs to be exported for control
class/gpio/unexport is used to notify the system to cancel the export
The class/gpio/gpiochipX directory stores the information of the GPIO registers in the system, including the starting number base, register name, and total number of pins controlled by each register. The steps to export a pin
| 07 | * To the /sys/class/gpio/gpio12 directory, if no corresponding directory appears, it means that this pin cannot be exported: |
class/gpio/export
| 10 | echo out > direction |
| 12 | * The value file is the numerical value of the port, which is 1 or 0. |
class/gpio
for i in gpiochip* ;
| 2 | GPIOE: 128 |
| 4 | GPIOG: 192 |
| 6 | GPIOB: 32 |
| 8 | GPIOD: 96 |
2. Calculate GPIO number
We use GPE11 to control LED.
The header of GPE0 is 128, and that of GPE11 is 128+11 = 139.
| 1 |
$ echo 139 > /sys/
class /gpio/gpio139/direction |
Then you can configure the output settings.
| 1 |
$ echo 1 > /sys/
class /gpio/gpio139/value |
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