PWM 0-13 channels are available on 2.54 mm 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 Navio2’s output channel number 1 and run the provided example. Do not forget to supply power to the servo rail.
If you have not already done that, download Navio2 drivers and examples code here.
If you have not build the examples yet, perform the following commands:
To check the PWM output example, you need to run this command:
Move to the folder with the code and run the example:
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 is necessary to update the value in
set_duty_cycle every 100 ms or less to make PWM output works.
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 second pin on the rail, you need to use
Then, you can write and read values.