在linux下控制gpio可以先用简单的命令行去控制下看看，

1. devmem 0x41200000 32

0x00000005

2.devicetree的结构如下

dip0: gpio_dip_sw@41200000 {

compatible = "generic-uio","uio";

reg =<0x41200000 0x1000>;

text_data = "GPIO_DIP_SWITCH"; //for test

bin_data=; //for test

};

需要注意的点是 reg=后面的一个参数必须要大于等于0x1000 ;

3. c语言源码

fd_led=open(filename,O_RDONLY);

if(fd_led<0)

return 1;

base_address = mmap(NULL, 0x10, PROT_READ | PROT_WRITE, MAP_SHARED, fd_led, 0);

if(base_address==MAP_FAILED)

{perror("mmap");

}

总结一下：

下面是完整的API函数

#include

#include

#include

// The specific GPIO being used must be setup and replaced thru

// this code. The GPIO of 240 is in the path of most the sys dirs

// and in the export write.

//

// Figuring out the exact GPIO was not totally obvious when there

// were multiple GPIOs in the system. One way to do is to go into

// the gpiochips in /sys/class/gpio and view the label as it should

// reflect the address of the GPIO in the system. The name of the

// the chip appears to be the 1st GPIO of the controller.

//

// The export causes the gpio240 dir to appear in /sys/class/gpio.

// Then the direction and value can be changed by writing to them.

// The performance of this is pretty good, using a nfs mount,

// running on open source linux, on the ML507 reference system,

// the GPIO can be toggled about every 4 usec.

// The following commands from the console setup the GPIO to be

// exported, set the direction of it to an output and write a 1

// to the GPIO.

//

// bash> echo 240 > /sys/class/gpio/export

// bash> echo out > /sys/class/gpio/gpio240/direction

// bash> echo 1 > /sys/class/gpio/gpio240/value

// if sysfs is not mounted on your system, the you need to mount it

// bash> mount -t sysfs sysfs /sys

// the following bash script to toggle the gpio is also handy for

// testing

//

// while [ 1 ]; do

// echo 1 > /sys/class/gpio/gpio240/value

// echo 0 > /sys/class/gpio/gpio240/value

// done

// to compile this, use the following command

// gcc gpio.c -o gpio

// The kernel needs the following configuration to make this work.

//

// CONFIG_GPIO_SYSFS=y

// CONFIG_SYSFS=y

// CONFIG_EXPERIMENTAL=y

// CONFIG_GPIO_XILINX=y

int main()

{

int valuefd, exportfd, directionfd;

printf("GPIO test running...\n");

// The GPIO has to be exported to be able to see it

// in sysfs

exportfd = open("/sys/class/gpio/export", O_WRONLY);

if (exportfd < 0)

{

printf("Cannot open GPIO to export it\n");

exit(1);

}

write(exportfd, "240", 4);

close(exportfd);

printf("GPIO exported successfully\n");

// Update the direction of the GPIO to be an output

directionfd = open("/sys/class/gpio/gpio240/direction", O_RDWR);

if (directionfd < 0)

{

printf("Cannot open GPIO direction it\n");

exit(1);

}

write(directionfd, "out", 4);

close(directionfd);

printf("GPIO direction set as output successfully\n");

// Get the GPIO value ready to be toggled

valuefd = open("/sys/class/gpio/gpio240/value", O_RDWR);

if (valuefd < 0)

{

printf("Cannot open GPIO value\n");

exit(1);

}

printf("GPIO value opened, now toggling...\n");

// toggle the GPIO as fast a possible forever, a control c is needed

// to stop it

while (1)

{

write(valuefd,"1", 2);

write(valuefd,"0", 2);

}

}

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