External Interrupt

[Bieli]

In this program the led should blinking every one second. The signal is taken from real time clock. But it blinked 8 sometimes 2 or 4 times and after it it stop. The low level is puted on RB0, but the interrupt don't delete it ( WRITE_PCF8583( 00, 04 ); ) so propably the interrupt isn't taken.
The problem can be coused that I use 16F874.h and 16F874A chip <- Is this problem or my code is wrong?

#include <16f874.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#include <b_lcd.c>

#define EEPROM_SDA PIN_C2
#define EEPROM_SCL PIN_C3

#include <PCF8583.c>

#int_ext
Przerwanie_T1()
{ output_bit(pin_d0,!input(pin_d0)); //Blinking led
WRITE_PCF8583( 00, 04 ); //Delete interrupt flag in PCF8583
}
main() {

enable_interrupts(global);
enable_interrupts(INT_EXT);
EXT_INT_EDGE(H_TO_L);
init_PCF8583();
lcd_init();

.....

do {
printf(lcd_putc,"\f\%X:\%X:\%X\n \%X-\%X \%X",READ_PCF8583(04),READ_PCF8583(03),READ_PCF8583(02),READ_PCF8583(05),READ_PCF8583(06),READ_PCF8583(00));
} while (TRUE);

}
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This message was ported from CCS's old forum
Original Post ID: 10673

[kolio]

Hi,
What will happen while execution of endless loop readings READ_PCF8583(xx) there appears an interrupt from RTC and in the middle of one reading at I2C bus ISR starts to write to RTC?
I don't know if at READ_PCF8583() the interrupts are previously disabled in order to avoid collisions, but you should prevent the asynchronous reference to RTC.
You can put TF clearing outside of ISR, like this:

short TF;
#int_ext
Przerwanie_T1()
{ output_bit(pin_d0,!input(pin_d0)); //Blinking led
TF = 1;
}
main() {

enable_interrupts(global);
enable_interrupts(INT_EXT);
EXT_INT_EDGE(H_TO_L);
init_PCF8583();
lcd_init();
TF = 0;

.....

do {
if(TF) {
WRITE_PCF8583( 00, 04 ); //Delete interrupt flag in PCF8583
TF = 0;
}
printf(lcd_putc,"\f\%X:\%X:\%X\n \%X-\%X \%X",READ_PCF8583(04),READ_PCF8583(03),READ_PCF8583(02),READ_PCF8583(05),READ_PCF8583(06),READ_PCF8583(00));
} while (TRUE);

}


According to me you shouldn't worry too much about the versions 874 and 874A.
Wish you luck!
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This message was ported from CCS's old forum
Original Post ID: 10677

[Tomi]

How do you attach the LED to D0 bit? Keep in mind that the input() function reads the pin so it could be 0 even if the LED lights. Additional problem that the input() function sets that pin to input first then the output_bit() function sets back it to output.
It would be better to use a RAM flag to set/reset it and then copy its state to pin_D0.

:=In this program the led should blinking every one second. The signal is taken from real time clock. But it blinked 8 sometimes 2 or 4 times and after it it stop. The low level is puted on RB0, but the interrupt don't delete it ( WRITE_PCF8583( 00, 04 ); ) so propably the interrupt isn't taken.
:=The problem can be coused that I use 16F874.h and 16F874A chip <- Is this problem or my code is wrong?
:=
:=#include <16f874.h>
:=#fuses HS,NOWDT,NOPROTECT,NOLVP
:=#use delay(clock=4000000)
:=#include <b_lcd.c>
:=
:=#define EEPROM_SDA PIN_C2
:=#define EEPROM_SCL PIN_C3
:=
:=#include <PCF8583.c>
:=
:=#int_ext
:=Przerwanie_T1()
:={ output_bit(pin_d0,!input(pin_d0)); //Blinking led
:= WRITE_PCF8583( 00, 04 ); //Delete interrupt flag in PCF8583
:=}
:=main() {
:=
:= enable_interrupts(global);
:= enable_interrupts(INT_EXT);
:= EXT_INT_EDGE(H_TO_L);
:= init_PCF8583();
:= lcd_init();
:=
:= .....
:=
:= do {
:= printf(lcd_putc,"\f\%X:\%X:\%X\n \%X-\%X \%X",READ_PCF8583(04),READ_PCF8583(03),READ_PCF8583(02),READ_PCF8583(05),READ_PCF8583(06),READ_PCF8583(00));
:= } while (TRUE);
:=
:=}
___________________________
This message was ported from CCS's old forum
Original Post ID: 10678