i.MX6UL -- PWM用户空间使用方法

i.MX6UL -- PWM用户空间使用方法

    开发平台： 珠海鼎芯D518--基于i.MX6UL

    开发系统： Linux4.1.15

    文件系统：Yocto-Busybox1.23

    基于iMX的PWM使用方法，这里将以PWM2作为示例，以下为PWM部分设置示例及解析：

root@imx6ulevk:~# cat /sys/kernel/debug/pwm/*查看当前PWM设备
*/
platform/20fc000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f8000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f4000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f0000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/208c000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/2088000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/2084000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/2080000.pwm, 1 PWM device
 pwm-0   (backlight           ): requested enabled
root@imx6ulevk:~#echo 0 >/sys/class/pwm/pwmchip1/export/*设置PWM输出，调出pwm0目录下设备节点，用于以下配置
*/

root@imx6ulevk:~# cat /sys/kernel/debug/pwm
platform/20fc000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f8000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f4000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/20f0000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/208c000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/2088000.pwm, 1 PWM device
 pwm-0   ((null)              ):
platform/2084000.pwm, 1 PWM device
 pwm-0   (sysfs              ): requested enabled
platform/2080000.pwm, 1 PWM device
 pwm-0   (backlight           ): requested enabled

root@imx6ulevk:~#cat/sys/class/pwm/pwmchip1/pwm0/{enable,period,duty_cycle}/*查看PWM使能、一个周期时间、一个周期中ON时间
*/
0
0
0
root@imx6ulevk:~#echo 1 >/sys/class/pwm/pwmchip1/pwm0/enable/*设置PWM2使能
*/
root@imx6ulevk:~#echo 1000000 >/sys/class/pwm/pwmchip1/pwm0/period/*设置PWM2一个周期的持续时间，单位为ns，即1K
Hz */
root@imx6ulevk:~#echo 500000 >/sys/class/pwm/pwmchip1/pwm0/duty_cycle/*设置一个周期中的”ON”时间，单位为ns，即占空比=duty_cycle/period=50%
*/
root@imx6ulevk:~#cat/sys/class/pwm/pwmchip1/pwm0/{enable,period,duty_cycle}
1
1000000
500000