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Bill_Smith
Joined: 06 Feb 2004
Posts: 26
Location: Curitiba, Brazil
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| PIC16F688 Interrupt-On-Change |
 Posted: Thu Mar 03, 2005 1:51 pm |
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Recently I needed to port a simple CCS C program that was running on a PIC16F88 to its cousin the PIC16F688. The original code used PORT B�s interrupt-on-change mechanism to capture when a switch was activated. As expected, each time the switch was activated (ON = 5V) I received an interrupt via (INT_RB) which I debounced, read the port to determine if the switch was HIGH or LOW, and then set a FLAG. The code worked fine and all was well.
After porting the code to the PIC16F688 I either recieve no interrupts at all when using enable_interrupt(INT_RA), or constant interrupts, indepentent of whether the switch is activated, when using enable_interrupt(INT_RA1). Apparently there are some differences in the way interrupt-on-change works on this part.
Does anyone have any experience with the PIC16F688, specifically using PORT A�s interrupt-on-change function? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 03, 2005 2:08 pm |
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Did you:
1. Disable the comparators ?
2. Configure Port A pins as digital ?
3. Enable the appropriate pins for Interrupt-on-Change by
writing to the IOCA register ?
4. Read Port A, to clear the mis-match condition before exiting
from the ISR ?
If you still can't make it work, then post a small but complete test
program. Be sure to show all #fuses, #use delay(), etc., statements. |
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Bill_Smith
Joined: 06 Feb 2004
Posts: 26
Location: Curitiba, Brazil
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| Posted: Thu Mar 03, 2005 4:36 pm |
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Thank you once again PCM Programmer. You were correct in determining that I had not setup PORT A properly.
As a treat for all the newbies, I am listing a version of the program which shows how to implement interrupt-on-change for the PIC16F688.
| Code: |
#include <16F688.h>
#use delay(clock=4000000)
#fuses NOWDT,INTRC_IO,NOMCLR,NOPROTECT,BROWNOUT,NOCPD
#zero_ram
// Inputs
#define Switch_ON input(PIN_A2) // SIGNAL INPUT
#define Switch_OFF !input(PIN_A2)
// Outputs
#define LED_On output_low(PIN_C4) // INDICATOR OUTPUT
#define LED_Off output_high(PIN_C4)
#define FREQLOW 331 // 90 Pulses Per Minute (PPM)
#define FREQHIGH 161 // 180 Pulses Per Minute (PPM)
int8 STATE=0x00; //|--XX--|--XX--|--XX--|--XX--|--XX--|--XX--|--XX--| SW1 |
void Flash(void);
#int_TIMER0
void TIMER0_isr(void)
{
set_timer0(34250); // Delay ~13ms @ 4MHz
if(Switch_ON)
bit_set(STATE,0);
else
bit_clear(STATE,0);
disable_interrupts(INT_TIMER0); // Stop Timer 0
}
#int_RA
RA_isr(void)
{
enable_interrupts(INT_TIMER0); // Start Timer 0
}
void main(void)
{
setup_oscillator(OSC_4MHZ,0);
setup_adc_ports(NO_ANALOGS); // Make PORT A Inputs Digital
setup_adc(ADC_OFF); // Turn OFF ADC
setup_comparator(NC_NC_NC_NC); // Disconnect Comparators
set_tris_a(0b00110100); // |--XX--|--XX--|TRISA5|TRISA4|TRISA3|TRISA2|TRISA1|TRISA0|
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_256);
enable_interrupts(INT_RA2); // Enable Interrupt-On-Change
enable_interrupts(GLOBAL);
sleep(); // Wait for the switch to close
while(1)
{
switch(STATE) // To add more switches, add more cases
{
case 0x00: // Switch is OFF
sleep(); // Go back to sleep
break;
case 0x01: // Switch is ON
Flash(); // Do something
break;
default: // Who cares
sleep(); // Go back to sleep
break;
}
}
}
void Flash(void)
{
LED_On;
delay_ms(FREQLOW);
LED_Off;
delay_ms(FREQLOW);
}
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Have fun.
Bill |
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gg
Guest
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| Posted: Mon Sep 03, 2007 12:17 am |
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| I just found the problem. Make sure to disable comparators. |
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