newbie need interrupt help

[morebudwiser]

hi the problem that i have with my program is that i want to call a function from the main program and loop round this function until an interrupt is recived on port b this is were the problem comes when the interrupt has happened i do not want to return to the instruction that was going to be excuted next in the function i want to jump to the the start of my main progam again as shown in my code below but i can not get the following code to compile it comes up with the error undefined lable that was used in a goto. Any help with problem would be much apperictaed. here is the code i am trying to get working . This is not actual program i am wrirting but this is what i want to be able to do


#include <16F877A.H>
#device ICD=TRUE
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#include <Button.c>

#define
/**********************************isr*********************/
#int_Ext
void LIMIT_switch(void)
{
goto start; // go to start of main program
}

/****************************ledflash**********************/


void led_flash()
{
while (1)
{
output_low(PIN_C0); // loop until interrupt is recived
delay_ms(500);
output_high(PIN_C0);
delay_ms(500);
}
}

/***********************************************************/

void main()
{
int8 A0 = 0;
set_tris_c(0x00);
port_b_pullups(true);
ext_int_edge(0,H_TO_L);
enable_interrupts(INT_EXT);
enable_interrupts(global);



while (1)
{
start:
if(button(PIN_A0, 0, 50, 10, A0, 1)) //wait for button press on pin A0
led_flash();
}



}

[rwyoung]

Good luck with stack management jumping out of your interrupt like that. Probably not restoring flags either. Look at your LST file to see what you have done.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

[asmallri]

You may have a reason for restarting your code that is not obvious from the example and description you have given. If not then this is not the right way to approach the problem. One way (there are many) would be to set a global flag "found_it" in the interrupt handler. Then in led_flash() test the state of the flag to detemine if you should exit the function and clear the flag. If you need to exit immediately without completing any delay_ms(500) in progress then I suggest replacing the delay_ms function with your own timer driven code which supports continuous polling of the flag.

Another (cleaner?) approach is to use a timer interrupt to toggle the LEDS. Setup timer2 to interrupt every 10ms and a counter with a value of 50. Every time a timer interrupt occues decrement the counter. If the counter reaches zero then toggle the LED and reset the counter to 50. Then in the Ext_Int handler you stop timer 2. Your main loop could use the state of the timer 2 on/off condition to perform a conditional operation (like reinitialise)....
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Mark]

Lookup reset_cpu()

[asmallri]

[Mark]

Yes,

[morebudwiser]

hi thanks for the replys, the progam i am actual trying to write controls a stepper motor.the main progarm controls an lcd menu selection that allows me to set variables for controlling the speed and the amonut of times the motor rotates. The other function controls the motor what i am trying to do with the intrerrupt is stop the motor and return to the main lcd selection menu. could you please give me a short example of how i could do this using a global flag or is there any books that anyone could recommend that would give me some programming examples

[PCM programmer]