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Serial port and Interrupts

 
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gerhard
Guest
Serial port and Interrupts
PostPosted: Sun Apr 04, 2004 2:34 pm     Reply with quote
Hello,

I am using the PIC18F8720 (MPLAB6.40, CCS PCH (3.148)) and have the following problem:
I use the RS232 port to control a graphic display. When do not use interrupts everything works fine, but as soon as I enable int_rb I get garbage on the display (the whole time).

Here is the code:
Code:

#include <18F8720.h>
#fuses  HS,NOWDT,noprotect,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=pin_d5,rcv=pin_d4,stream=a)

#int_rb
void rb_isr()
{
   putc(27,a);
   printf("ZL");
   putc(150,a);
   putc(150,a);
   printf("Some text");
   putc(0,a);
}

void main()
{
   enable_interrupts(global);
   enable_interrupts(INT_RB);

   putc(27,a);
   printf("DL");
   
   putc(27,a);
   printf("ZL");
   putc(100,a);
   putc(100,a);
   printf("test");
   putc(0,a);

   while(true)
   {}   
}


Any suggestions?

Gerry
Ttelmah
Guest
Re: Serial port and Interrupts
PostPosted: Sun Apr 04, 2004 2:46 pm     Reply with quote
gerhard wrote:
Hello,

I am using the PIC18F8720 (MPLAB6.40, CCS PCH (3.148)) and have the following problem:
I use the RS232 port to control a graphic display. When do not use interrupts everything works fine, but as soon as I enable int_rb I get garbage on the display (the whole time).

Here is the code:
Code:

#include <18F8720.h>
#fuses  HS,NOWDT,noprotect,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=pin_d5,rcv=pin_d4,stream=a)

#int_rb
void rb_isr()
{
   putc(27,a);
   printf("ZL");
   putc(150,a);
   putc(150,a);
   printf("Some text");
   putc(0,a);
}

void main()
{
   enable_interrupts(global);
   enable_interrupts(INT_RB);

   putc(27,a);
   printf("DL");
   
   putc(27,a);
   printf("ZL");
   putc(100,a);
   putc(100,a);
   printf("test");
   putc(0,a);

   while(true)
   {}   
}


Any suggestions?

Gerry

You enable the port b _change_ interrupt. Then you never read port b, so this interrupt will never be reset. The interrupt routine will be continuously called...
To use the RB interrupt, _read_ port B before enabling it, and read it again inside the interrupt handler. The handler will then be called only when the port changes.

Best Wishes
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