Am335x 之GPIO控制

转载http://blog.csdn.net/hudaweikevin/article/details/16336411

请注明原处，谢谢。QQ：343556608

参考：http://processors.wiki.ti.com/index.php/GPIO_Driver_Guide

目前还没有涉及到代码（后续会有新的博客更新），仅关注到用户空间对GPIO的控制。

1.执行下面的命令，可以显示目前驱动已经申请到的IO状态

$ mount -t debugfs debugfs /sys/kernel/debug

$ cat /sys/kernel/debug/gpio

root@am335x-evm:/# cat /sys/kernel/debug/gpio

GPIOs 0-31, gpio:

gpio-2 (volume-up ) in hi

gpio-3 (volume-down ) in hi

gpio-6 (mmc_cd ) in hi

GPIOs 32-63, gpio:

gpio-48 (wlan_en ) out lo

gpio-53 (matrix_kbd_col ) out hi

gpio-54 (matrix_kbd_col ) out hi

gpio-57 (matrix_kbd_row ) in lo

gpio-58 (matrix_kbd_row ) in lo

gpio-59 (matrix_kbd_row ) in lo

GPIOs 64-95, gpio:

GPIOs 96-127, gpio:

gpio-114 (mmc_wp ) in lo

gpio-117 (bt_en

) out lo

2，重新申请一个新IO，但注意看一下原理图，最好是没有使用的IO，如果本身的IO在其它地方使用的话，有可能申请不到或是破坏设备。

下面我们申请118，并且查看有没有申请成功

root@am335x-evm:/# echo 118 > /sys/class/gpio/export

root@am335x-evm:/# ls /sys/class/gpio

export gpiochip0 gpiochip64 unexport

gpio118 gpiochip32 gpiochip96

root@am335x-evm:/# cat /sys/kernel/debug/gpio

GPIOs 0-31, gpio:

gpio-2 (volume-up ) in hi

gpio-3 (volume-down ) in hi

gpio-6 (mmc_cd ) in hi

GPIOs 32-63, gpio:

gpio-48 (wlan_en ) out lo

gpio-53 (matrix_kbd_col ) out hi

gpio-54 (matrix_kbd_col ) out hi

gpio-57 (matrix_kbd_row ) in lo

gpio-58 (matrix_kbd_row ) in lo

gpio-59 (matrix_kbd_row ) in lo

GPIOs 64-95, gpio:

GPIOs 96-127, gpio:

gpio-114 (mmc_wp ) in lo

gpio-117 (bt_en

) out lo

gpio-118 (sysfs ) in lo

3，改变IO为输出：

root@am335x-evm:/# echo "out" > /sys/class/gpio/gpio118/direction

使IO的输出为高：

root@am335x-evm:/# echo 1 > /sys/class/gpio/gpio118/value

root@am335x-evm:/# cat /sys/kernel/debug/gpio

GPIOs 0-31, gpio:

gpio-2 (volume-up ) in hi

gpio-3 (volume-down ) in hi

gpio-6 (mmc_cd ) in hi

GPIOs 32-63, gpio:

gpio-48 (wlan_en ) out lo

gpio-53 (matrix_kbd_col ) out hi

gpio-54 (matrix_kbd_col ) out hi

gpio-57 (matrix_kbd_row ) in lo

gpio-58 (matrix_kbd_row ) in lo

gpio-59 (matrix_kbd_row ) in lo

GPIOs 64-95, gpio:

GPIOs 96-127, gpio:

gpio-114 (mmc_wp ) in lo

gpio-117 (bt_en

) out lo

gpio-118 (sysfs ) out hi

4，释放IO，

root@am335x-evm:/# echo 118 > /sys/class/gpio/unexport

总结：这种模式我觉得在调试某些简单IO控制的一些设备的时候很方便，比如硬件用到一个IO开关某一设备，那么就几条命令就可以控制好了。如果用做学习，大家可以手工来点灯。