Connecting two PIC18F starter kits using USART2 - c

Question

I want to connect two PIC18F starter kits (with PIC18F46J50), using RS232. Since USART1 is already connected to the card reader (integrated), I need to use USART2 (I need to remap RX2/TX2 to RP19/RP20 pins-RD2/RD3).
I already found some demo code for SENDING:
#define _XTAL_FREQ 8000000 //The speed of your internal(or)external oscillator
#include <p18cxxx.h>
#include <usart.h>
int i = 0;
// CONFIG1L
#pragma config WDTEN = OFF // Watchdog Timer (Disabled - Controlled by SWDTEN bit)
#pragma config PLLDIV =3 // PLL Prescaler Selection bits - Divide by 3 (12 MHz oscillator input)
#pragma config STVREN = ON // Stack Overflow/Underflow Reset (Enabled)
#pragma config XINST = OFF // Extended instruction set disabled
// CONFIG1H
#pragma config CPUDIV = OSC1 // CPU System Clock Postscaler (No CPU system clock divide)
#pragma config CP0 = OFF // Code Protect (Program memory is not code-protected)
// CONFIG2L
#pragma config OSC = HSPLL //HS oscillator, PLL enabled, HSPLL used by USB
#pragma config T1DIG = ON // T1OSCEN Enforcement (Secondary Oscillator clock source may be selected)
#pragma config LPT1OSC = OFF // Low-Power Timer1 Oscillator (High-power operation)
#pragma config FCMEN = OFF //Fail-Safe Clock Monitor disabled
#pragma config IESO = OFF //Two-Speed Start-up disabled
// CONFIG2H
#pragma config WDTPS = 32768 // Watchdog Postscaler (1:32768)
// CONFIG3L
#pragma config DSWDTOSC = INTOSCREF // DSWDT Clock Select (DSWDT uses INTRC)
#pragma config RTCOSC = T1OSCREF // RTCC Clock Select (RTCC uses T1OSC/T1CKI)
#pragma config DSBOREN = OFF // Zero-Power BOR disabled in Deep Sleep
#pragma config DSWDTEN = OFF // Deep Sleep Watchdog Timer (Disabled)
#pragma config DSWDTPS = 8192 //1:8,192 (8.5 seconds)
// CONFIG3H
#pragma config IOL1WAY =OFF //IOLOCK bit can be set and cleared
#pragma config MSSP7B_EN = MSK7 // MSSP address masking (7 Bit address masking mode)
// CONFIG4L
#pragma config WPFP = PAGE_1 // Write/Erase Protect Page Start/End Location (Write Protect Program Flash Page 0)
#pragma config WPEND = PAGE_0 //Start protection at page 0
#pragma config WPCFG = OFF //Write/Erase last page protect Disabled
// CONFIG4H
#pragma config WPDIS = OFF //WPFP[5:0], WPEND, and WPCFG bits ignored
#define USE_AND_MASKS
unsigned char Txdata[] = "MICROCHIP_USART";
void Delay1Second(void);
void main (void)
{
unsigned char spbrg=0,baudconfig=0,i=0;
// REMAPE ID PORT
PPSCON = 0x00; // unlock peripheral Pin select register
RPOR19 = 0x05; // assign USART2 TX to RP19/RD2
RPINR16 = 0x14; // assign USART2 RX to RP20/RD3
PPSCON = 0x01; // lock peripheral Pin select register
TRISDbits.TRISD2 = 0; // TX2 output
TRISDbits.TRISD3 = 1; // RX2 input
//------USART Setup ----
Close2USART(); //turn off usart if was previously on
spbrg = 51;
Open2USART(USART_TX_INT_OFF &
USART_RX_INT_OFF &
USART_ASYNCH_MODE &
USART_EIGHT_BIT &
USART_CONT_RX &
USART_BRGH_HIGH, spbrg);
baudconfig = BAUD_8_BIT_RATE & BAUD_AUTO_OFF;
baud2USART (baudconfig);
PORTB = 0x03;
while(1){
//------USART Transmission ----
while(Busy2USART()); //Check if Usart is busy or not
puts2USART((char *)Txdata); //transmit the string
Delay1Second();
Close2USART();
}
}
void Delay1Second()
{
for(i=0;i<100;i++)
{
__delay_ms(10);
}
}
I connected the two boards using two wires (on D2 and D3 pins), and I want to send a string from board1 to board2. I think I need to use interrupts to read, but I haven't found any demo code. Also, I don't know if the configuration pins are ok.
Can somebody show me how to receive the sent text to board no.2?

Answer 1

I will assume that you did the wiring correctly.
You don't need interrupts to receive. It can be useful but it's not required. To receive your string, you just have to do :
gets2USART( str, 10 );
If your string if 10 characters long (including the null terminator).
If you want to receive a string of an arbitrary length, you may write your own gets2USART to read until the null terminator. It is actually quite simple, here is the source code of gets2USART to help you :
void gets2USART(char *buffer, unsigned char len)
{
char i; // Length counter
unsigned char data;
for(i=0;i<len;i++) // Only retrieve len characters
{
while(!DataRdy2USART());// Wait for data to be received
data = getc2USART(); // Get a character from the USART
// and save in the string
*buffer = data;
buffer++; // Increment the string pointer
}
}
Also, here is the source code of puts2USART :
void puts2USART( char *data)
{
do
{ // Transmit a byte
while(Busy2USART());
putc2USART(*data);
} while( *data++ );
}
You can see that there already is a while(Busy2USART());, so you don't need to add one. It is logical, because the UART is byte wise, so it is busy when it sends a byte, and the function needs to check for every byte.
Also, you are closing the UART after use, but actually loop to redo the sending. Since you just closed the UART, that won't work.