PIC32MX: Digital Inputs

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 Inputs Example

This section uses an example to describe how to set up and read digital inputs using a PIC32MX460F512L.

Sample Code

Program to display push-button input as LED (on board) output

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 constant INPUT_G0 which reads the digital input. PORTx reads on port x the current value of the pin (in this case G0).

  #define INPUT_G0       PORTGbits.RG0

Begin main body of program.

  int main(void){

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

  SYSTEMConfigPerformance(80000000L);

Initialize the LEDs on the board. This function may be different depending on the hardware profile. This function is for UBW32.

  mInitAllLEDs();

The pin that we want to use as an input must be initialized as an input. 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 TRISG &= Hex number; We use &= hex number to only change the pins that we want to set as inputs / outputs.

  TRISGbits.TRISG0=1;

Use while to set up infinite loop.

   while(1)
       {

// What we're going to do is blink an LED on and off // depending on whether or not digital input is high or low. if (INPUT_G0) { mLED_3_On(); } else { mLED_3_Off(); }

       }
   }