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ccs2015
Joined: 18 Mar 2015
Posts: 2
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| Interrupt-On-Change not working in PIC12F1822 |
 Posted: Wed Mar 18, 2015 8:24 am |
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Hello, if I run this code on a PIC12F1822 it works, the LED toggles when there is a falling-edge in BUTTON pin:
| Code: | #include <12F1822.h>
#device adc = 10
#use delay(int=8000000)
#fuses NOWDT,NOPROTECT,NOCPD,NOMCLR,PUT,INTRC_IO,NOBROWNOUT,NODEBUG,NOWRT
#define LED PIN_A2
#define BUTTON PIN_A1
int1 flag;
void main()
{
setup_adc_ports(NO_ANALOGS);
while(1){
if(!input(BUTTON))
output_toggle(LED);
}
} |
But when I want to use interrupt-on-change doing these changes:
| Code: |
void main()
{
setup_adc_ports(NO_ANALOGS);
enable_interrupts(INT_RA1_H2L);
enable_interrupts(GLOBAL);
while(1){
if(flag){
output_toggle(LED);
delay_ms(500);
flag = 0;
}
}
}
#INT_RA
void int_ioc()
{
if(!input(BUTTON))
flag = 1;
}
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The LED does not blink. I have tried with and without an external pull-up in BUTTON pin, and configuring enable_interrupts(INT_RA1) instead of enable_interrupts(INT_RA1_H2L).
What could be the problem?
I am using MPLAB 8.92, CCS 4.140 and the ICD2 programmer.
Regards. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19359
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| Posted: Wed Mar 18, 2015 8:44 am |
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These chips have an extra bit that has to be cleared to exit the interrupt.
With the standard 'interrupt on change', two things have to be done in the interrupt to clear it. Read the port, and clear the interrupt flag (you do the first, and the compiler does the second). However on these chips, you also have to clear the mask bit that says which bit has interrupted. So:
| Code: |
#byte IOCAF = getenv("SFR:IOCAF")
#INT_RA
void int_ioc()
{
bit_clear(IOCAF,1); //For RA1
if(!input(BUTTON))
flag = 1;
}
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Without this bit cleared, the interrupt flag won't clear, so the interrupt will never exit....
You clear the bit corresponding to the interrupt you are using.
Since you are not using any others you could just use:
IOCAF=FALSE;
Which clears them all. |
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ccs2015
Joined: 18 Mar 2015
Posts: 2
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| Posted: Wed Mar 18, 2015 8:51 am |
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| Thanks a lot Ttelmah, it is working now. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19359
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| Posted: Wed Mar 18, 2015 10:30 am |
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It's one of those 'once you know about it, dead easy, but designed to confuse' things.  |
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