More than four character Rx and Tx through UART

[varma]

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 ? 

[AJISH ALFRED]

Hi Varma,

You could have make the query more simple rather than talking about the working of a piece of code first up. You haven’t mentioned anything about your project that you are doing, which microcontroller, which IDE, where you want to show the output, your circuit etc. 

Since you know that your are getting unexpected results, the reasons should be also unexpected. 

Please post the details and explain the trouble your are facing in such a way that it will be easy for others to understand.

 

[varma]

dsPIC30F5011 / MPLAB8.8

 

 

HI, 

 

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

 

wrote an ISR.

configured bits as 

 

<code>

 

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

</code>

 

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

<code>

 

#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 != ‘’)

{

        while(U1STAbits.UTXBF); // wait if the buffer is full

                 U1TXREG = *buffer++;     // transfer data word to TX reg

        }

    }

    else 

{

             while(*temp_ptr != ‘’) 

        {

                 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);

        

} 

 

</code>

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