PIC32MX: PWM Motor Control

Pulse Width Modulation, or PWM, is a technique used to vary the average magnitude of a signal by changing its duty cycle (the proportion of time that a signal is active or "high"). For a more in-depth introduction to PWM motor control click here.

PWM for PIC32 is discussed in more detail in the Microchip Output Compare documention.

Available Pins

The pins available for PWM are 5 input pins (OC1, OC2, OC3, OC4, and OC5) and 2 output pins (OCFA and OCFB). The output pins are for fault pin protection.

General Approach

PWM can be set up by either changing the directly altering register bits or using the functions in outcompare.h (a header file included in the peripheral library (plib.h). The latter case is more straightforward and easier. This wiki describes how to use the outcompare functions. The register bits approach is described in detail in theMicrochip Output Compare documention.

There are three main functions that are used for PWM.

  void OpenOCX( config, value1, value2)

where X is the module that you want to use (1-5). This function configures the OCX module and loads the R and RS registers with default values. An example is shown below:

  OpenOC1( OC_ON | OC_TIMER2_SRC | OC_PWM_FAULT_PIN_DISABLE, 0, 0);

The different configurations are shown below. If not specified, the default configuration is used.

OC_ON	Turns the Module ON
OC_OFF	Default - Turns the Module Off

Unidirectional Motor Control

This section will detail how to set up a simple program and circuit to control a motor using a PIC microcontroller and PWM.