这篇文档主要介绍如何使用硬件PWM(Pulse Width Modulation)。
设置以及打开PWM
PWM_F:
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| $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/export $ echo 1000000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/period $ echo 500000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/duty_cycle $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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PWM_D:
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| $ echo 1 | sudo tee /sys/class/pwm/pwmchip1/export $ echo 1000000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/period $ echo 500000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/duty_cycle $ echo 1 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
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PWM_F:
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| $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/export $ echo 1000000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/period $ echo 500000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/duty_cycle $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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PWM_F:
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| $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/export $ echo 1000000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/period $ echo 500000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/duty_cycle $ echo 1 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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如果你成功开启了硬件PWM,你可以通过示波器看到波形:
注意如果使用示波器去查看波形,记得板子和示波器需要共地。
关闭PWM
1
| $ echo 0 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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1
| $ echo 0 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
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1
| $ echo 0 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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1
| $ echo 0 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
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