PIC18f2550 RS-232 Programming example in CCS PICC

In previous post, we showed a DIY prototyping board for PIC18F2550. That board has a block of RS-232 to TTL converter but it was not tested. We will test that block here separately. 

CCS PICC has a built-in library of RS-232. It doesn't need to configure all related registers in SFR to make this module work. Its primary task is to add the #use rs232() directive in source code. This directive needs the #use delay(clock=x) directive to be declared first. For example,

#use delay (clock=4M)

#use RS232(uart1,baud=9600)

C directive showed above inform the compiler to use 4MHz clock frequency. Default UART is uart1 for most of PIC micro-controller that come with USART module inside. The baud rate is set to 9600.

UART communication for 8-bit are RC6 for transmission (Tx), and RC7 for reception (Rx). UART data I/O functions are just like the ANSI C library function. For example printf() is use for outputting ASCII data from micro-controller from its Tx pin. Other ANSI C functions are usable in CCS PICC such as getc(), putc(), kbhit(), etc.

This example will show how to use these RS-232 functions with PIC18F2550 micro-controller.

#include <18f2550.h>

//use external 20MHz crystal oscillator 

#fuses HS,NOWDT,PLL1,CPUDIV1

#use delay(clock=20M)

#use rs232(uart1,baud=9600)

void main(void){

   char temp1=0;

   //Clear PortC

   output_C(0x00);

   //PortC as output

   set_tris_C(0x00);

   printf("PIC18F2550 USB Board\n\r");

   printf("Please enter number between 0 and 3\n\r");

   printf("to toggle RC1 and RC2.\n\r");

   while(1){    

   //Test buffer

      if(kbhit()){

            temp1=getc();

            putc(temp1);

      }

      switch(temp1){

         case '0':

            output_low(pin_c1);

            temp1=0;

            printf("\tRC1 is OFF.\n\r");

            break;

         case '1':

            output_high(pin_c1);

            temp1=0;

            printf("\tRC1 is ON.\n\r");

            break;

         case '2':

            output_low(pin_c2);

            temp1=0;

            printf("\tRC2 is OFF.\n\r");

            break;

         case '3':

            output_high(pin_c2);

            temp1=0;

            printf("\tRC2 is ON.\n\r");

            break;

         case 0:

            break;

         default:

            printf("\n\rPlease enter number between 0 and 3\n\r");

            printf("to toggle RC1 and RC2.\n\r");

            temp1=0;

            break;

      }

   }

}

I tested this example on my prototyping board.

Program testing on prototyping board

Host PC and PIC18F2550 side sending/receive data

I run this testing using a desktop PC with COM port on Windows 7 64-bit. The serial terminal showed above is a part of CCS PICC compiler IDE.