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Software Uart and External Interrupt issue

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david90

Joined: 25 Feb 2006
Posts: 23

Software Uart and External Interrupt issue

Posted: Sun Feb 20, 2011 4:48 pm

Code:

//tested code with dev board.
#include <12F683.h>
#device adc=8

#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC //Internal RC Osc
#FUSES NOCPD //No EE protection
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOMCLR //Master Clear pin used for I/O
#FUSES NOPUT //No Power Up Timer
#FUSES BROWNOUT //Reset when brownout detected
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES FCMEN //Fail-safe clock monitor enabled

#use delay(clock=8000000)
#use rs232(baud=2400,parity=N,xmit=PIN_A1,rcv=PIN_A2,bits=8,errors)

int buffer[10];
int i=0;
int open_detected=0;
int close_detected=0;
void main()
{
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC);
setup_vref(FALSE);
setup_oscillator(OSC_8MHZ);

enable_interrupts(INT_EXT);
ext_int_edge( H_TO_L );
enable_interrupts(GLOBAL); //enable interrupt

while(1)
{
output_high(PIN_A5);
delay_ms(100);
output_low(PIN_A5);
delay_ms(100);

if (open_detected==1)
{
output_high(PIN_A0);
delay_ms(100);
output_low(PIN_A0);
delay_ms(100);
output_high(PIN_A0);
delay_ms(100);
output_low(PIN_A0);
delay_ms(100);
open_detected=0;
}
if (close_detected==1)
{
output_high(PIN_A0);
delay_ms(100);
output_low(PIN_A0);
delay_ms(100);
close_detected=0;
}

}
}

#INT_EXT //use external pin int to avoid polling for serial data. Software UART does not have INT.
void INT_EXT_handler() {
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
buffer[0]=getc();

if ((buffer[0]==0x57 && buffer[1]==0xA9) || (buffer[0]==0x5F && buffer[1]==0xA1))
{
open_detected=1;
}

if (buffer[0]==0xDF && buffer[1]==0x21)
{
close_detected=1;
}
}

Whenever I power on my PIC, it immediately goes into the INT_EXT ISR and get stuck there until I send serial data to the PIC. I know for a fact that when I power up my pic, the pic doesn't even go to my infinite while loop but instead goes directly to the ISR. Why does this happen? There might be a chance that this happens because of my dev board.

temtronic

Joined: 01 Jul 2010
Posts: 9221
Location: Greensville,Ontario


Posted: Sun Feb 20, 2011 4:57 pm

You might want to enable the PowerUpTimer ( PUT) as well as and a small delay in Main before the interrupts are enabled. Depending on the board layout, power supply specs, etc. you might already have an interrupt from something 'glitchy'.

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Mon Feb 21, 2011 12:36 am

Quote:

Whenever I power on my PIC, it immediately goes into the INT_EXT ISR

Read this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=43138

Quote:

shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);
shift_left(buffer,10,0);

Why do this ? Just use a pointer or an array index.

Quote:

#FUSES INTRC

If you change this fuse to INTRC_IO then you can also use PIN_A4
as an i/o pin.

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