2022-10-28 14:41:25 Technology sharing

1:Brief introduction

In the embedded systemGPIOThe operation is the most basic operation. existLinuxThere is a generalGPIOOperation method, letusink below to introduce to it “/sys/class/gpio” Way.

In/sys/class/gpio/BelowexportFile, XiangexportThe file is written to operateGPIONo.GPIOThe operate interface is exposed from the kernel space to the user space,GPIOThe operate interface includesdirectionandvalueetc.directioncontrolGPIOInput or output mode, andvalueCan controlGPIOState or read status. 

/sys/class/gpio/Each file description in the directory:

/sys/class/gpio/exportThe file is used to inform the system that needs to be exported to controlGPIOPin number；

/sys/class/gpio/unexport   Used to notify the system to cancel the export;

/sys/class/gpio/gpioX/directionFile, you can writein(Set input direction) orout(Set output direction);

/sys/class/gpio/gpioX/valueThe file can be read and writeGPIOstate;

/sys/class/gpio/gpiochipXDirectory storage systemGPIOThe information of the register, including the starting number of each registers Control pin, the name of the register, the total number of pins; among themXRepresents specific pins numbers.

 

1:operateGPIO

1.1: First calculate this pin number

Pin number = CONTROL pins, register bases + Control pins register number

for example: RisaG2LChip as an example, dual -coreA55Processor, Gundam1.2GHZ, Industrial -grade chips, high stability, good cost -effective.

If you want to use P43_2Then Pin Number may be equal to 43 x 8 + 2 + 120 = 466。

GPIO_ID = GPIO_port *   8 + GPIO_pin + 120                   

 

1.2:ExportThis pins

Towards /sys/class/gpio/export Write this number, for exampleP43_2Pin, in shell It can be implemented through the following command:

root@weathink:~# echo 466 > /sys/class/gpio/export      

After the command is successful /sys/class/gpio/ P43_2 Directory, if there is no corresponding directory, it means that this pin cannot be exported.

 

1.3:Direction

direction The file, define the input input direction, can be defined as output by the following command.

root@weathink:~#  echo out >   /sys/class/gpio/P43_2/direction      

 

direction Accept parameters can be:in、out、high、lowEssence The parameters high / low While setting the direction to the output, it will value Set to the corresponding 1 / 0。

 

1.4:GPIOOutput

value The file is the value of the port, for1or0，通过下面命令将P43_2 设置为高电平。

使用echo命令来设置GPIO

root@weathink:~# echo 1 >   /sys/class/gpio/P43_2/value

root@weathink:~# echo 0 >   /sys/class/gpio/P43_2/value

 

1.5:读取GPIO值

root@weathink:~# cat   /sys/class/gpio/P43_2/value         

如果返回1表示高电平，返回0Indicates a low level.

 

 

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