User Manual

Library Reference

The driver consists of the following functions, which you can use to drive the underlying hardware when writing your

own application in Python:

Initialize Object

You can create a new object for each HAT with

pwm = PWM(0x40)

In this case, pwm (lowercase) is the object created, and PWM(0x40) is the creation call. By default, all HATs are

address 0x40, but by changing the address jumpers, you can create objects that use other addresses such as 0x60,

0x42, etc.

setPWMFreq(self, freq)

Description

This function can be used to adjust the PWM frequency, which determines how many full 'pulses' per second are

generated by the IC. Stated differently, the frequency determines how 'long' each pulse is in duration from start to

finish, taking into account both the high and low segments of the pulse.

Frequency is important in PWM, since setting the frequency too high with a very small duty cycle can cause problems,

since the 'rise time' of the signal (the time it takes to go from 0V to VCC) may be longer than the time the signal is

active, and the PWM output will appear smoothed out and may not even reach VCC, potentially causing a number of

problems.

Arguments

freq: A number representing the frequency in Hz, between 40 and 1000

Example

The following code will set the PWM frequency to the maximum value of 1000Hz:

setPWM(self, channel, on, off)

Description

This function sets the start (on) and end (off) of the high segment of the PWM pulse on a specific channel. You specify

the 'tick' value between 0..4095 when the signal will turn on, and when it will turn of. Channel indicates which of the

16 PWM outputs should be updated with the new values.

Arguments

channel: The channel that should be updated with the new values (0..15)

on: The tick (between 0..4095) when the signal should transition from low to high

off:the tick (between 0..4095) when the signal should transition from high to low

Example

pwm.setPWMFreq(1000)