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PWM output

PWM output

PWM 0-13 channels are available on 2.54mm header pins numbered 1-14 accordingly. Servos can be controlled by setting the correct frequency (50hz is a common frequency) and duty cycle corresponding to the length of a pulse (usually between 1 and 2 milliseconds).

To try to control servo connect the servo to the Navio’s output channel number 1 and run the provided example. Do not forget to supply power to the servo rail.

If you haven't already done that, download Navio2 drivers and examples code here.

C++

Move to the folder with the source code, compile and run the example

cd C++/Examples/Servo
make
sudo ./Servo

Python

Move to the folder with the code and run the example

cd Python
sudo python Servo.py

For further information see cource code. Note that set_period function sets the period for PWM_OUTPUT channel depending on frequency value, which passed as a second parameter to the function.

To set the pulse range appropriate for your servo you can change the SERVO_MIN and SERVO_MAX values.

Kernel driver for Navio2 that generates PWM needs to be fed with data at least every 100 ms. So it’s necessary to update the value in set_duty_cycle every 100 ms or less to make PWM output works.

GPIO support

The servo rail pins also might be operated as GPIOs.

You can use /sys/class/gpio/gpiochip500 to control pins on the servo rail by

echo N > /sys/class/gpio/export

Where N equals 500 + header pin number - 1. So in order to control the 2nd pin on the rail, you need to echo 501.

Then you can write and read values.