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IMX6Q PWM frequency is not correct

Question asked by Zhongjian sun on Apr 10, 2018
Latest reply on Apr 12, 2018 by Zhongjian sun

hi,

   I have a problem with imx6q pwm. 

I use 

echo 0 >/sys/class/pwm/pwmchip1/export

echo 100 >/sys/class/pwm/pwmchip1/pwm0/period

echo 50 >/sys/class/pwm/pwmchip1/pwm0/duty_cycle

echo 1 >/sys/class/pwm/pwmchip1/pwm0/enable

I set pwm period is 100ns, duty_cycle 50ns, means that the pwm frequency is 10MHz, duty is 50%, but the oscilloscope shows the pwm frequency is 11MHz, and when the period is 92-100, the frequency is always 11MHz, when the period is 90, the frequency is 13.2MHz. 

why is that? I check the pwm clock ,is 66MHz.

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