PIC16F627A UART interrupt problems

sunyean · Joined: 01 Oct 2005 Posts: 2

I am working with 16F627. I want to use a UART's receive interrupt and TIMER0 interrupt simultaneously. and use PORT B (PIN7~PIN5) as output.
I failed to operate them.

At first, when TIMER0 interrupt is active, UART interrupt does not work.
when I set the PORT direction using set_tris_b(), UART itself does not work. And disabled TIMER0 interrupt , UART interrupt works very well.

Anyway, I have to do trade-off coding Crying or Very sad

for these codes. I really should use All these interrupt and PORT B as the same time.

What are problems here ?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

1. Add NOLVP to the #fuses statement.
#fuses XT,NOWDT,NOBROWNOUT, NOLVP

2. Add the ERRORS parameter to the #use rs232() statement.
#use RS232(baud=9600, XMIT=PIN_B2,RCV=PIN_B1, ERRORS)

3. Change the RTCC preload value so it doesn't interrupt at
such a high rate. With such a short interval between
interrupts, there is probably not enough time to process
the current interrupt before another one occurs.
Try setting it to:

set_rtcc(0x00);

Do that in both places in your code.

Hans Wedemeyer · Joined: 15 Sep 2003 Posts: 226

Try this.
TIMER0 is fast... Dop as PCMProgrammer says and adjust your timer to be somwhat slower!

Ths will work, if the incoming data stream has a small time dealy between each byte.

#include <16f627a.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>

#define LIMIT 255

#fuses XT,NOWDT,NOBROWNOUT
#use delay (clock=4000000) // ????? = 4MHz
#use RS232(baud=9600, XMIT=PIN_B2,RCV=PIN_B1)

int count=0;
int RxFlag;
int RxData;

#byte RCREG = 0X1A

#int_rda
void int_rcv()
{
RxData=RCREG; // get byte and clear interrupt flag
RxFlag++; // tell the main loop something arrived...

// do NOT do this in the interrupt routine
// char c;
// putc(c=getc()); NO
}
////////////////////////////////////////////////////////////////////
//
#int_rtcc
void int_tmr0()
{
count ++;
set_rtcc(0xfe);
}
///////////////////////////////////////////////////////////////////
//
void main()
{

byte value = 0x00; // Port B? ???
byte RED = 0x00;
byte GREEN = 0x00;
byte BLUE = 0x00;

set_tris_b(0x00);
output_b(0x00);

setup_counters(RTCC_INTERNAL,RTCC_DIV_16); // Timer0 ??
enable_interrupts(INT_RTCC); // Timer interrupt ??

enable_interrupts(INT_RDA);

enable_interrupts(GLOBAL);

set_rtcc(0xfe); // Timer0 ??? ??

RxFlag=0;
while(1)
{
if(RxFlag)
{
putc(RxData);
RxFlag=0;
}
}
}

sunyean · Joined: 01 Oct 2005 Posts: 2

still not working Crying or Very sad

sunyean · Joined: 01 Oct 2005 Posts: 2

I tested the code which is modified for 16F73.

SUCCESS!!

Of course, As time value setted in TIMER0 is very large, UART must be working well. when time value is small, UART did not work also.

but, I adopted the same code to 16F627, even though time value is small, it's failded.

In conclusion, PIC16F627 has a weak point when TIMER0 and UART REV interrupts are used simultaneously.

If assembler, it may be OK ^^;