UART sending random character on terminal. Why?

[Rickooo]

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 :

// 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:

#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++);
}

 

[KlausST]

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

 

[paulfjujo]

hello,

Where is the main code ?

 

[Rickooo]

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

 

[paulfjujo]

hello,


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

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);

 

[Rickooo]

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?

 

[KlausST]

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

 

[Rickooo]

hello,


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

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);

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

 

[paulfjujo]

hello,


i forget to modify here

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

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

 

[Rickooo]

hello,


i forget to modify here

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

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

Thank you. I got the value print using sprintf function.