Setting the PCA9685 PWM module prescaler
From old awnser of the adafruit forum, the PCA9685 is not very precise.
So you have to manually check and adapt the prescaler value.

My math are correct according to page 25 of the datasheet and 102 should indeed generates a frequency of 59.84Hz.

However my oscilloscope measurement gives me this :

110 = 60.24Hz
111 = 59.52Hz


TL:DR ; due to the low precision of this component the prescaler computation only gives you a close estimate, you will have to measure the real thing with an oscilloscope.

see second post : https://forums.adafruit.com/viewtopic.php?f=19&amp;t=72554

Blue = real, measured with my oscilloscope

Red = from the datasheet formula