PWM Example
Emlid OES Prime 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:
“`bash
/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.
“`bash
root@OES Prime:~# ls /sys/class/pwm/pwmchip0
device export npwm power subsystem uevent unexport
“`
Activate the PWM:
“`bash
echo 0 > /sys/class/pwm/pwmchip0/export
“`
Set period to 10ms:
“`bash
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:
“`bash
echo “normal” > /sys/class/pwm/pwmchip0/pwm0/polarity
“`
Enable the PWM:
“`bash
echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable
“`
Set duty cycle to 1ms:
“`bash
echo 1000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
“`
You can connect logic analyzer to “`PWM0“` pin and see the result:
