More than four characters Tx and Rx through UART

[MKVRAJU]

I am trying to transmit a string and raised receive interrupt as
taking buf[20]

void _attribute__((__interrupt__,no_auto_psv)) _U1RXInterrupt(void){  // This is UART1 receive ISR 
          IFS0bits.U1RXIF = 0; 
          for(i=0;i<20;i++) 
            buf = ReadUART1(); 
          putsUART1((unsigned int*)buf); 
}

I used

U1MODEbits.LPBACK	= 0;    // Disable Loop Back

U1STAbits.URXISEL = 2;    // Interrupt flag bit is set when Receive Buffer is 3/4 full (i.e., has 3 data characters)

when i am using value 2 here , the loop discontinues when 3 data characters are filled and remaining array is replaced by 3 char.
when i am using value 3 here, the loop discontinues when 4 data char are filled
when i am using value 0 or 1 , it prints the same what typed ,with out filling the char array.


where does my logic go wrong ? I want to print a string of length for example " this is test".
I want to get
[TX] : this is test
[RX] : this is test


In the case if I want to add a big paragraph, i cannot mention a particular size like buf[20], then how to initialize ?

 

[jayanth.devarayanadurga]

Post your full code. Post function definition of putsUART1().

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Code C - [expand]
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for(i=0;i<20;i++) 
    //i is global variable
    buf[i++] = ReadUART1();
    buf[i] = '\0';
        
} 
 
 
 
putsUART1((unsigned int*)buf);  //assumed putsUART1() prints string

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[MKVRAJU]

HI jayanth,

I have initilized a buffer array , char buf[24];

wrote an ISR as you mentioned

configured bits as

U1STAbits.UTXISEL	= 1;    // Interrupt when a character is transferred to the Transmit Shift register
    U1STAbits.UTXBRK 	= 0;    // Operate U1Tx Normally on Transmit Break Bit
    U1STAbits.UTXEN  	= 1;    // Enable U1 Tranmission   
   
    U1STAbits.URXISEL 	= 0;    // Interrupt flag bit is set when Receive Buffer is 3/4 full (i.e., has 1 data characters)
                                         //  b00 or b01 for 1 letter buffer size, b10 for 3 letter buffer , 11 for 4 letter buffer size

I could absolutely send and receive 1,3,4 chars respectively. And I can now understand that bufarray is being over written in last digits as I shown in the picture.

Now my problem is I want to transmit more than 4 letters at once and then receive.So for an example I have randomly chosen 24 chars .
If I write value for U1STAbits.URXISEL , the interrupt automatically breaks up when the buffer is full with 1 or 3 or 4 chars, as mentioned in the data sheet of the processor.

how do I write for a 24 char similarly ? Do I need to write a seperate ISR for this ? then how ? but I cannot use _U1TXInterrupt vector then.
Suggest me a way to do it ?


code for UART.c

#include<P30F5011.h>
#include"UART1.h"
char buf[24];
int j;

void  init_UART1()                    // Initialization function.
{                                                      
	
	TRISFbits.TRISF3 	= 0;    	  // Configure RF3 as Output for UART1 Tx .
	TRISFbits.TRISF2	= 1;		  // Configure RF2 as Input for UART1 Rx.
	
   /********************* CONFIGURE UART1 Baud Rate Generator Register *********************
        *                      					*
        * FCY : 8 MHz, 							*
      	* Desired Baud Rate : 9600    / 19200   * 
      	* Desired U1BRG = 25 or 0x19h / 0x33 	*
      	*                      					*
   ****************************************************************************************/
    U1BRG    = 51;  //XT /w PLL 4x
							
    /************************* CONFIGURE UART1MODE Register********************************/
    U1MODEbits.USIDL	= 0;    // Continue operation in Idle mode
    U1MODEbits.ALTIO	= 0;    // UART communicates usingalternate UxTX and UxRX I/O pins
    U1MODEbits.WAKE 	= 1;    // Enable Wake up
    U1MODEbits.LPBACK	= 0;    // Disable Loop Back
    U1MODEbits.ABAUD	= 0;    // Disable Auto Baud
    U1MODEbits.PDSEL	= 0;    // 8 Bit Data, No Parity
    U1MODEbits.STSEL	= 0;    // 1 Stop Bit
    
    IPC2bits.U1TXIP 	= 7;    // Tx priority level.
    IPC2bits.U1RXIP 	= 7;	// Rx priority level.
    
    U1MODEbits.UARTEN	= 1;    // Enable UART
    
    IEC0bits.U1TXIE		= 1;    // Enabling TX interrupt.
    IEC0bits.U1RXIE		= 1;    // Enabling Rx interrupt.

    
         
    /********************* CONFIGURE UART1 STATUS & CONTROL Register ***********************/
    U1STAbits.UTXISEL	= 1;    // Interrupt when a character is transferred to the Transmit Shift register
    U1STAbits.UTXBRK 	= 0;    // Operate U1Tx Normally on Transmit Break Bit
    U1STAbits.UTXEN  	= 1;    // Enable U1 Tranmission   
   
    U1STAbits.URXISEL 	= 0;    // Interrupt flag bit is set when Receive Buffer is 3/4 full (i.e., has 1 data characters)
  // 	putsUART1((unsigned int *)"UART Ready");
	
 } 



void putsUART1(unsigned int *buffer)
{
	char * temp_ptr = (char *) buffer;         	// transmit till NULL character is encountered      
	if(U1MODEbits.PDSEL == 3)                  // check if TX is 8bits or 9bits
	{			       	
		while(*buffer != '\0')
		{
        	while(U1STAbits.UTXBF); 			// wait if the buffer is full
                 U1TXREG = *buffer++;    		// transfer data word to TX reg
        }
    }
    else 
	{
             while(*temp_ptr != '\0') 
	         {
                 while(U1STAbits.UTXBF);   // wait if the buffer is full 
                 U1TXREG = *temp_ptr++;    // transfer data byte to TX reg 
             }
    }
}


void __attribute__((__interrupt__,no_auto_psv)) _U1TXInterrupt(void) // This is UART1 transmit ISR
{
    IFS0bits.U1TXIF = 0;
    
    
}

void __attribute__((__interrupt__,no_auto_psv)) _U1RXInterrupt(void) // This is UART1 receive ISR
{
	      IFS0bits.U1RXIF = 0;
	      for(j=0;j<=24;j++)
	          buf[j]=ReadUART1();
    	      
              putsUART1((unsigned int*)buf);
        
}

 

[jayanth.devarayanadurga]

Use break if buffer is filled with 1 char. What I mean by buffer is the receive register of UART. You should send a terminating null character at the end of data so that once the end of data is received then the data is transmitted back.

Post the .c file.