The only difference is I try to keep sending the string "OK" out without receiving any characters and I use PIC18F4550.
- CODE: SELECT_ALL_CODE
//=============================================================================
// Filename: Example_uart.c
//-----------------------------------------------------------------------------
// Compiled using MPLAB-C18 v3.34 student edition
//=============================================================================
// Company : Cytron Technologies, Malaysia
// Revision : 1.00
// Date : 28 Dec 2009
//=============================================================================
#include <p18f4550.h>
#include "delays.h"
//=============================================================================
// Configuration Bits
//=============================================================================
/** CONFIGURATION **************************************************/
#pragma config PLLDIV = 5 // (20 MHz crystal on PICDEM FS USB board)
#pragma config CPUDIV = OSC1_PLL2
#pragma config USBDIV = 2 // Clock source from 96MHz PLL/2
#pragma config FOSC = HSPLL_HS
#pragma config FCMEN = OFF
#pragma config IESO = OFF
#pragma config PWRT = OFF
#pragma config BOR = ON
#pragma config BORV = 3
#pragma config VREGEN = ON //USB Voltage Regulator
#pragma config WDT = OFF
#pragma config WDTPS = 32768
#pragma config MCLRE = ON
#pragma config LPT1OSC = OFF
#pragma config PBADEN = OFF
// #pragma config CCP2MX = ON
#pragma config STVREN = ON
#pragma config LVP = OFF
// #pragma config ICPRT = OFF // Dedicated In-Circuit Debug/Programming
#pragma config XINST = OFF // Extended Instruction Set
#pragma config CP0 = OFF
#pragma config CP1 = OFF
// #pragma config CP2 = OFF
// #pragma config CP3 = OFF
#pragma config CPB = OFF
// #pragma config CPD = OFF
#pragma config WRT0 = OFF
#pragma config WRT1 = OFF
// #pragma config WRT2 = OFF
// #pragma config WRT3 = OFF
#pragma config WRTB = OFF // Boot Block Write Protection
#pragma config WRTC = OFF
// #pragma config WRTD = OFF
#pragma config EBTR0 = OFF
#pragma config EBTR1 = OFF
// #pragma config EBTR2 = OFF
// #pragma config EBTR3 = OFF
#pragma config EBTRB = OFF
//=============================================================================
// Define Pins
//=============================================================================
#define PIC_CLK 20000000
#define BAUD 9600
//#define DIVIDER ((PIC_CLK/(16UL * BAUD) -1))
#define DIVIDER ((PIC_CLK/BAUD)/16) -1
#define HIGH_SPEED 1
#define LOW_SPEED 0
#define sw1 PORTBbits.RB0 //Active Low
#define sw2 PORTBbits.RB1
//=============================================================================
// Function Prototypes
//=============================================================================
void Delay_1msX (unsigned int miliseconds);
void Delay_100msX (unsigned int msec);
int uart_init(){
// SPBRGH = 0;
SPBRG = DIVIDER; //set baud rate to 9600 for 20Mhz
TXSTAbits.BRGH = HIGH_SPEED; //baud rate high speed option
TXSTAbits.SYNC = 0; //Asynchronous mode
RCSTAbits.SPEN = 1; //Serial port enable
RCSTAbits.CREN = 1; //enable reception.
TXSTAbits.TX9=0; //8-bit transmission
RCSTAbits.RX9=0; //8-bit reception
TXSTAbits.TXEN=0; //reset transmitter
TXSTAbits.TXEN=1; //enable the transmitter
TRISC = 0b10000000; // RC7 = RX = input, RC6 = TX = output
return 1;
}
void clear_usart_error(void)
{
if (RCSTAbits.OERR)
{
TXSTAbits.TXEN=0;
TXSTAbits.TXEN=1;
RCSTAbits.CREN=0;
RCSTAbits.CREN=1;
}
if (RCSTAbits.FERR)
{
TXSTAbits.TXEN=0;
TXSTAbits.TXEN=1;
}
}
void uart_send(char data)
{
while(!PIR1bits.TXIF);
TXREG = data;
}
char uart_rec(void)
{
while(!PIR1bits.RCIF)
{
clear_usart_error();
}
return RCREG;
}
void uart_string(unsigned char *str_ptr)
{
while(!PIR1bits.TXIF);
while (*str_ptr)
{
uart_send(*str_ptr);
str_ptr++;
}
return;
}
//=============================================================================
// Global Variables
//=============================================================================
unsigned int i, t;
unsigned char data_tx, data_rx;
//=============================================================================
// Main Program
//=============================================================================
void main ()
{
//set I/O input output
TRISB = 0b00000011; //Configure PORTB I/O direction
TRISC = 0b10000000; //Configure PORTC I/O direction
TRISD = 0b00000000; //Configure PORTD I/O direction
PORTB = 0;
PORTC = 0;
PORTD = 0;
//-------------------------------------------------------------------------
// Configure UART
//-------------------------------------------------------------------------
/*
OpenUSART (USART_TX_INT_OFF & //Transmit interrupt off
USART_RX_INT_OFF & //Receive interrupt off
USART_ASYNCH_MODE & //Asynchronous mode - UART
USART_EIGHT_BIT & //8-bit transmit/receive
USART_CONT_RX & //Continuous reception
USART_BRGH_HIGH, //High baudrate
129); //9600 baudrate at 20MHz frequency
*/
uart_init();
while(1)
{
//-------------------------------------------------------------------------
// UART Transmit
//-------------------------------------------------------------------------
data_tx='O'; //Assign data
uart_send(data_tx); //Send data through UART
data_tx='K'; //Assign data
uart_send(data_tx); //Send data through UART
}
}//End of main
//=============================================================================
// Subroutines
//=============================================================================
/********************************************************************
* Function Name: Delay_1msX *
* Return Value: void *
* Parameters: miliseconds: amount of delay *
* Description: This routine generates various delays *
* needed by xlcd functions. *
* For delay of 1ms (18F4550 running at 48MHz) *
* Cycles = (TimeDelay * Fosc) / 4 *
* Cycles = (1ms * 48MHz) / 4 *
* Cycles = 12,000 *
* Since call of function also takes some *
* instruction cycles, the exact value to get *
* 1ms delay is less than 12,000. *
********************************************************************/
void Delay_1msX (unsigned int miliseconds)
{
t=0;
while(t<miliseconds)
{
Delay1KTCYx(11);
Delay10TCYx(96);
Nop();
Nop();
Nop();
Nop();
Nop();
t++;
}
}//End of Delay_1msX
/********************************************************************
* Function Name: Delay_100msX *
* Return Value: void *
* Parameters: miliseconds: amount of delay *
* Description: This routine generates various delays *
* needed by xlcd functions. *
* For delay of 100ms *
* (18F4550 running at 48MHz) *
* Cycles = (TimeDelay * Fosc) / 4 *
* Cycles = (100ms * 48MHz) / 4 *
* Cycles = 1,200,000 *
* Since call of function also takes some *
* instruction cycles, the exact value to get *
* 1ms delay is less than 1,200,000. *
********************************************************************/
void Delay_100msX (unsigned int msec)
{
t=0;
while(t<msec)
{
Delay10KTCYx(119);
Delay1KTCYx(9);
Delay10TCYx(96);
t++;
}
}//End of Delay_100msX
Then I try to receive the characters from the PC side using a RS232 converter and eventually I receive garbage characters, can anyone help?
In this program, it receive 0xAD for both "O" and "K"...
solved: it should be #pragma config FOSC = HS instead of #pragma config FOSC = HSPLL_HS.
can anyone tell me the reasons?
