PIC32MX: Digital Outputs

Working with digital inputs and outputs is fundamental to circuit design, and PIC microcontrollers add versatility to design by allowing programming and re-programming of the logic associated with input and output pins. In this way, one PIC microcontroller can take the place of many pre-programmed digital logic ICs.

Digital Output Example

This section describes how to set up and write digital outputs using a PIC32MX460F512L.

Sample Code

Program to turn on LEDs based on User Switch of UBW32. swUser must be defined for a switch (digital input) if not using UBW32.

First include header files with definitions for generic type definitions, compiler, and for specific PIC. Also include the plib header file.

  #include "GenericTypeDefs.h"
  #include "Compiler.h"
  #include "HardwareProfile.h"
  #include <plib.h>

NOTE THAT BECAUSE WE USE THE BOOTLOADER, NO CONFIGURATION IS NECESSARY. THE BOOTLOADER PROJECT ACTUALLY CONTROLS ALL OF OUR CONFIG BITS.

Define a constants for 4 output pins. LATx is the function used to write to a pin.

  #define PIN_D4			LATDbits.LATD4
  #define PIN_D5			LATDbits.LATD5
  #define PIN_D6			LATDbits.LATD6
  #define PIN_D7			LATDbits.LATD7

Begin main body of program.

  int main(void){

Configure the proper PB frequency and number of wait states in this case 80MHz.

  SYSTEMConfigPerformance(80000000L);

Set all analog pins to be digital I/O

  AD1PCFG = 0xFFFF;

Turn off JTAG so we get the pins back

  mJTAGPortEnable(0);

The pins that we want to use as outputs must be initialized as an outputs. TRISx is a register that sets the pin as an input (1) or an output(0). You can set entire ports as inputs / outputs by using TRISX &= Hex number; We use &= hex number to only change the pins that we want to set as inputs / outputs.

Set D4, D5, D6, and D7 as a digital outputs

  LATD |= 0x00F0; TRISD &= 0xFF0F;

Use while to set up infinite loop. What we're going to do is blink LEDs on the board on and off depending on whether the user switch is pressed.

   while(1)
   {
       if(swUser)
       {
          PIN_D4 = 1;
          PIN_D5 = 0;
          PIN_D6 = 1;
          PIN_D7 = 0;
       }
       else
       {
          PIN_D4 = 0;
          PIN_D5 = 1;
          PIN_D6 = 0;
          PIN_D7 = 1;
       }
    }
  } // end main