Test for the high level servo driver.
A servo connected to PWM_0 channel 0 should move back and forth inside the
angle -90 degrees to +90 degrees, approximately.
Using a scope should show a varying pulse length between 1000 us to 2000 us long. The requested frequency is 100 Hz, but due to hardware limitations it might not be possible to achieve the selected frequency. The pulse width should, however, remain the same, only the frequency of pulses (and hence the duty cycle) should differ.