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How to make INT_RB work for multiple RS 232 ports on 16F877A

 
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arunb



Joined: 08 Sep 2003
Posts: 492
Location: India

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How to make INT_RB work for multiple RS 232 ports on 16F877A
PostPosted: Sun Jul 30, 2006 8:03 am     Reply with quote
Hi,

I have written some code on receiving ascii on multiple RS 232 ports using the INT_Rb interrupt.

I can receive some characters but not the correct ones, the drivers I am using are the standard MAX 232 type, and the hardware works when I use the timed_getc() function.

Here is the code for the transmitter/receiver PIC 16F877A mcu

thanks
arunb

Code:

#include <16F877A.h>


#FUSES HS,NOWDT,PUT,NOPROTECT,NOCPD,BROWNOUT,NOLVP,NODEBUG

#define EEPROM_SDA  pin_c4
#define EEPROM_SCL  pin_c3   
#define EEPROM_SIZE   0x7FF8


#use delay(clock=16000000)

#use rs232(baud=9600,xmit=pin_c6, rcv=pin_c7,parity=n,stream=PC,ERRORS)
#use rs232(baud=1200,xmit=pin_d5, rcv=pin_b5,parity=n,brgh1ok,stream=DISPLAY,force_sw,sample_early)
#use rs232(baud=1200,xmit=pin_d7, rcv=pin_b3,parity=n,brgh1ok,stream=RHSDRIVE,force_sw,sample_early)
#use rs232(baud=1200,xmit=pin_d6, rcv=pin_b4,parity=n,brgh1ok,stream=LHSDRIVE,force_sw,sample_early)
#use i2c(master, sda=EEPROM_SDA, scl=EEPROM_SCL)

#define LHSRCV pin_b4
#define DISRCV pin_b5


int bDReady,lhs,disp;

#ZERO_RAM
void initialise()
{


   setup_adc(ADC_OFF );

   set_tris_a(0b11111111);
   set_tris_b(0b11111111);
   set_tris_d(0b00011111);
   set_tris_c(0b10111111);
   set_tris_e(0b11111111);


   output_float(pin_b4);
   output_float(pin_d6);
   
   output_float(pin_d5);
   output_float(pin_b5);
   
   
   output_float(pin_d7);
   output_float(pin_b3);


   enable_interrupts(INT_RB);
   enable_interrupts(INT_RDA);
   enable_interrupts(GLOBAL);

}

void main()
{

   initialise();
   do
   {
   
      if (bDReady==2)
      {
         putc(disp,PC);
         bDReady=0;
      }



   }while(TRUE);

}


#int_rda
void usart_isr()
{

   int g,val;
   
   g=getc();
   
   val=fputc(g,DISPLAY);


}

#int_rb
void multi_rs232()
{
   int h;

   h=input_b();


   if (bit_test(h,5)==0)
   {
      disp=fgetc(DISPLAY);
      bDReady=2;
   }


}



Here is the code for the reciver (that sends back the data)

Code:


#include <16F648A.h>

#use delay(clock=4000000)

#FUSES INTRC,NOWDT,PUT,NOPROTECT,NOMCLR,NOCPD,BROWNOUT,NOLVP
#use rs232(baud=1200,xmit=pin_b2, rcv=pin_b1,parity=n)

char cRcvData;

#ZERO_RAM
void initialise()
{

  setup_comparator(NC_NC_NC_NC);
  set_tris_a(0b101111100);
  set_tris_b(0b111111011);

  enable_interrupts(INT_RDA);
  enable_interrupts(GLOBAL);

}

void main()
{
   initialise();

   do
   {



   }while(TRUE);

}

#int_rda
usart_rcv()
{
   cRcvData=getc();
   delay_us(100);
   putc(cRcvData+1);
}
Ttelmah
Guest
PostPosted: Sun Jul 30, 2006 10:15 am     Reply with quote
A series of comments.
First, get rid of the fputc, inside the serial interrupt handler. The putc, at 1200bps, will take eight character times of the hardware serial. If more than two character come in succession, you will lose data.
Second comment. the int_rda, needs to fgetc(PC). By default, a 'getc', without a stream, when multiple streams are enabled, selects the _last_ defined stream. Wrong one for the hardware serial...
Third comment. BRGH10K, does nothing on software streams. There is also no point in using 'force_sw', on pins that don't support hardware mode.
Now you presumably do understand, that if a second character arrives on either stream supporting interrupts, while the 'reply' is being sent to DISPLAY, this reply will be garbaged.
The delays in the int_rda on the second chip, should be removed. Have the reply sent in the _main_ not in the interrupt handler.

Best Wishes
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