UART sending random character on terminal. Why?

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Rickooo

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Hi, I am ussing PIC18F4520 microcontroller. I want to display circuit information using UART RS232. I am using PIC development board which have inbuilt connection to Rx Tx pin of UARt to C6 and C7 pin of controller. I am using HyperTerminal to display the read. XTAL = 16M, baudrate is 9600

When I am using UART_Write_Text function, it display random character.

Config :
Code:
// CONFIG1H
#pragma config OSC = HS         // Oscillator Selection bits (HS oscillator)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
#pragma config IESO = OFF       // Internal/External Oscillator Switchover bit (Oscillator Switchover mode disabled)

// CONFIG2L
#pragma config PWRT = OFF       // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bits (Brown-out Reset enabled and controlled by software (SBOREN is enabled))
#pragma config BORV = 3         // Brown Out Reset Voltage bits (Minimum setting)

// CONFIG2H
#pragma config WDT = OFF        // Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))
#pragma config WDTPS = 32768    // Watchdog Timer Postscale Select bits (1:32768)

// CONFIG3H
#pragma config CCP2MX = PORTC   // CCP2 MUX bit (CCP2 input/output is multiplexed with RC1)
#pragma config PBADEN = ON      // PORTB A/D Enable bit (PORTB<4:0> pins are configured as analog input channels on Reset)
#pragma config LPT1OSC = OFF    // Low-Power Timer1 Oscillator Enable bit (Timer1 configured for higher power operation)
#pragma config MCLRE = ON       // MCLR Pin Enable bit (MCLR pin enabled; RE3 input pin disabled)

// CONFIG4L
#pragma config STVREN = ON      // Stack Full/Underflow Reset Enable bit (Stack full/underflow will cause Reset)
#pragma config LVP = OFF        // Single-Supply ICSP Enable bit (Single-Supply ICSP disabled)
#pragma config XINST = OFF      // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode disabled (Legacy mode))

// CONFIG5L
#pragma config CP0 = OFF        // Code Protection bit (Block 0 (000800-001FFFh) not code-protected)
#pragma config CP1 = OFF        // Code Protection bit (Block 1 (002000-003FFFh) not code-protected)
#pragma config CP2 = OFF        // Code Protection bit (Block 2 (004000-005FFFh) not code-protected)
#pragma config CP3 = OFF        // Code Protection bit (Block 3 (006000-007FFFh) not code-protected)

// CONFIG5H
#pragma config CPB = OFF        // Boot Block Code Protection bit (Boot block (000000-0007FFh) not code-protected)
#pragma config CPD = OFF        // Data EEPROM Code Protection bit (Data EEPROM not code-protected)

// CONFIG6L
#pragma config WRT0 = OFF       // Write Protection bit (Block 0 (000800-001FFFh) not write-protected)
#pragma config WRT1 = OFF       // Write Protection bit (Block 1 (002000-003FFFh) not write-protected)
#pragma config WRT2 = OFF       // Write Protection bit (Block 2 (004000-005FFFh) not write-protected)
#pragma config WRT3 = OFF       // Write Protection bit (Block 3 (006000-007FFFh) not write-protected)

// CONFIG6H
#pragma config WRTC = OFF       // Configuration Register Write Protection bit (Configuration registers (300000-3000FFh) not write-protected)
#pragma config WRTB = OFF       // Boot Block Write Protection bit (Boot block (000000-0007FFh) not write-protected)
#pragma config WRTD = OFF       // Data EEPROM Write Protection bit (Data EEPROM not write-protected)

// CONFIG7L
#pragma config EBTR0 = OFF      // Table Read Protection bit (Block 0 (000800-001FFFh) not protected from table reads executed in other blocks)
#pragma config EBTR1 = OFF      // Table Read Protection bit (Block 1 (002000-003FFFh) not protected from table reads executed in other blocks)
#pragma config EBTR2 = OFF      // Table Read Protection bit (Block 2 (004000-005FFFh) not protected from table reads executed in other blocks)
#pragma config EBTR3 = OFF      // Table Read Protection bit (Block 3 (006000-007FFFh) not protected from table reads executed in other blocks)

// CONFIG7H
#pragma config EBTRB = OFF      // Boot Block Table Read Protection bit (Boot block (000000-0007FFh) not protected from table reads executed in other blocks)


Here is the code:
Code:
#ifndef _XTAL_FREQ
#define _XTAL_FREQ 16000000UL
#endif

#include <xc.h>
#include "uart.h"


char UART_Init(const long int baudrate)
{
unsigned int x;
    x = (_XTAL_FREQ - baudrate*64)/(baudrate*64);
    if(x>255)
    {
        x = (_XTAL_FREQ - baudrate*16)/(baudrate*16);
        TXSTAbits.BRGH =1 ;
    }
    if(x<256)
    {
      SPBRG = x;
      TXSTAbits.SYNC = 0;  //Asynchronous
      RCSTAbits.SPEN = 1;
      //**Select 8-bit mode**// 
      TXSTAbits.TX9 = 0; // 8-bit reception selected
      RCSTAbits.RX9 = 0; // 8-bit reception mode selected
      RCSTAbits.CREN = 1;
      TXSTAbits.TXEN = 1;
      TRISCbits.TRISC7 = 1;
      TRISCbits.TRISC6 = 1;
      INTCONbits.GIE = 1;
      INTCONbits.PEIE = 1;
      
      return 1;
    }
    return 0;
}

char UART_TX_Empty()
{
  return TXSTAbits.TRMT;
}

char UART_Data_Ready()
{
   return PIR1bits.RCIF;
}
char UART_Read_Char()
{
 while (!PIR1bits.RCIF) ;  // wait for data receive
 if(RCSTAbits.OERR) // check for Error
    {
     RCSTAbits.CREN = 0;  //If error -> Reset
     RCSTAbits.CREN =1 ;  //If error -> Reset
    }
  //while(!PIR1bits.RCIF);
  return RCREG;
}

void UART_Read_Text(char *Output, unsigned int length)
{
    unsigned int i;
    for(int i=0;i<length;i++)
        Output[i] = UART_Read_Char();
}

void UART_Write_Char (char data)
{
    
  while(!PIR1bits.TXIF);
    
  //while (TXSTAbits.TRMT == 0)
  TXREG = data;
}

void UART_Write_Text(char *text)
{
    while(*text)
      UART_Write_Char(*text++);
}
 

Hi,

Debug:
Write one known character (maybe 0x40) per second.
Then tell us
* how many chracters per second arrive and
* which value they are.

Klaus
 

Hi, I did nothing. And I just change the terminal. It display text there. But, now I want to display the value of "function called"
For example, if I want to display the value of "buff"
unsigned char buff;
do{
buff = response();
count++;
}while((buff!=0X01) && (count<10) );
how will I print the value of buff? When I used, UART_Write_Text, t just print nothing.

The code is same as above mentioned code in post #1
 

hello,


you must use a buffer , not a simple char named buff


Code:
unsigned char buff[32];

// better is  to  initialise the buffer
for (count=0;count<32;count++) buff[count]=0;  // 0 = string terminator

count=0;
do
{
buff[count] = response();
count++;
}
while((buff!=0X01) && (count<10) );

UART1_Write(13);
UART1_Write(10);
UART1_Write_Text(buff);
UART1_Write(13);
UART1_Write(10);
 

unsigned char buff[32]; // better is to initialise the buffer for (count=0;count<32;count++) buff[count]=0; // 0 = string terminator
Can you tell me, why you have added uART write 13 and 10?
 

Hi,

In case you don't know what 10 and 13 as ASCII characters stand for...it is [LF]= linefeed and [CR] = carriage return respectively.
Or you can always try to do an internet search like "UART 10 13".
The first hit gives the explanation ... and many others, too..

Klaus
 

Hello, As per you asked me to add the following code, I did.
I got:
 

hello,


i forget to modify here

Code:
....
}
while((buff[count]!=0X01) && (count<10) );

from where comes Buff! with 'B' as uppercase ?
 

hello,


i forget to modify here

Code:
....
}
while((buff[count]!=0X01) && (count<10) );

from where comes Buff! with 'B' as uppercase ?
Thank you. I got the value print using sprintf function.
 

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