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PWM

PWM Example

Emlid Neutis has two available PWM pins. In this example, we are using PWM0, which is the alternative function of URX0 pin. By default, it is disabled.

To enable it you should apply special Device Tree overlay by editing /boot/Env.txt. You need to add pwm to the overlays section:

/boot/Env.txt:

loglevel=10
overlays=pwm

Save this file and reboot your device. When your system finished booting, you should get pwmchip0 interface in sysfs.

root@neutis:~# ls /sys/class/pwm/pwmchip0
device  export  npwm  power  subsystem  uevent  unexport

Activate the PWM:

echo 0 > /sys/class/pwm/pwmchip0/export

Set period to 10ms:

echo 10000000 > /sys/class/pwm/pwmchip0/pwm0/period

It means that the signal is high for 10% of the period and low the other 90%.

Set normal polarity:

echo "normal" > /sys/class/pwm/pwmchip0/pwm0/polarity

Enable the PWM:

echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable

Set duty cycle to 1ms:

echo 1000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle

You can connect logic analyzer to PWM0 pin and see the result: