[ngohaibac]

Chào các bạn.

Đây là thư viện UART có chức năng tự detect Baud Rate. Khi muốn sử dụng chức năng này thì các bạn gọi hàm void UART_detectBaudRate(void);, khi đó trên PC phải truyền kí tự U để PIC đồng bộ tốc độ. Sau đó thì truyền nhận sẽ theo tốc độ đặt trên PC.

Đây là hàm UART.h

// UART.h
//=======================================================================================
#ifndef _UART_H
#define _UART_H
//========================================================================================
#include "pic18.h"
// Define for UART
#define TX			RC6
#define RX 			RC7
#define TRIS_TX	TRISC6
#define TRIS_RX	TRISC7

//========================================================================================
// Declare sosme functions
void UART_Init(unsigned int BaudRate);
void UART_PrChar(unsigned char a);
void UART_PrString(const char* str);
unsigned char UART_Read(void);
void UART_detectBaudRate(void);
#endif

UART.c

// UART.h
# include "UART.h"
# include "pic18.h"
# include "sysdef.h"

//========================================================================================
// Initialize UART
void UART_Init(unsigned int BaudRate){
	unsigned int n;

// Configure BaudRate
	BRGH = 0; 				// Low speed.
	BRG16 = 1;				// 16-Bit Baud Rate Generator - SPBRGH and SPBRG

	// Baudrate = Fosc/[16(n+1)]  => n = ((Fosc/Baudrate)>>4) - 1;  n = SPBRGH: SPBRG;
	n = ((Fosc/BaudRate)>>4) - 1;
	SPBRG = n;
	
	SPBRGH = n>>8;
	
// Enable the asyncchronous serial port.
	SYNC = 0 ;				// Asynchronous mode	
	SPEN = 1;				// Serial port enable.
	TRIS_TX = 0;
	TRIS_RX = 1;

//Configure for Transmitter mode.	
	TXEN  = 1; 				// Transmit enable 

//Configure for Receiver mode
	CREN = 1;				// Enable the reception 

	RCIF = 0;
	RCIE = 1;				// Reception Interrupt Enable
	GIE = 1;					// Global Interrupt Enable
	PEIE = 1;				// Perapheral Interrupt Enable
}	

//=====================================================================================
void UART_PrChar(unsigned char a){
	while(!TRMT);
	TXREG = a;
}	
//=====================================================================================
void UART_PrString(const char* str){
	while(*str)
		UART_PrChar(*str ++);
}	
//=====================================================================================
unsigned char UART_Read(void){
	return (RCREG);
}	
//====================================================================================
void UART_detectBaudRate(void){
	TXSTA = 0b00100100;
	RCSTA = 0b10010000;
	BAUDCON = 0b00001001;
	
	while(ABDEN);
}

Chương trình test:

/*;========================================================
/*; Ten chuong trinh	: Test IO
; Nguoi thuc hien	: Ngo Hai Bac (NOHB)
; Ngay thuc hien	: 27/06/07
; Phien ban			: 1.0		
; Mo ta phan cung	: Dung PIC18F2525/2620/4525/4620 - thach anh 20MHz
; Trinh dich			: HTPIC 18V9.50				
;				
;----------------------------------------------------------------
; Ngay hoan thanh	: 
; Ngay kiem tra	: 
; Nguoi kiem tra	: 
;----------------------------------------------------------------
; Chu thich	: 		
;========================================================*/
// Include
# include "pic18.h"
# include "sysdef.h"
# include "UART.h"

// configuration
__CONFIG(1,HS & FCMDIS & IESODIS);
__CONFIG(2,BORV21 & PWRTDIS & WDTDIS);
__CONFIG(3,MCLREN & LPT1DIS & PBANDIS);
__CONFIG(4,DEBUGDIS & LVPDIS & STVRDIS & XINSTDIS);
__CONFIG(5,UNPROTECT);
__CONFIG(6,UNPROTECT);
__CONFIG(7,UNPROTECT);

// Receiver Interrupt Function
void RxIntFcn(void);
// Interrupt Function
void interrupt MyInt  (void) {
	if (RCIE && RCIF){
		RCIF = 0;
		RxIntFcn();	
	};
}
/*=====================================================================================
  Main function
=====================================================================================*/
void main(){
	unsigned char i;
	
	ADCON1 = 0x07;
	TRISA = 0x00;
	PORTA = 0xFF;
	
	TRISB = 0x00;
	PORTB = 0xFF;
	
	UART_Init(9600);
	UART_detectBaudRate();
	while(1);
}
// Implementation of some functions
void RxIntFcn(void){
	unsigned char temp;
	temp = UART_Read();
	UART_PrChar(temp);
}

Chúc các bạn thành công.