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evsource
Joined: 21 Nov 2006
Posts: 129
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| Very weird RTCC, InT_RDA, and delay_ms problem |
 Posted: Mon Feb 23, 2009 4:46 pm |
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I'm wondering if someone else can duplicate this error.
I'm using PCH 4.030, 18F2620.
If I put a delay in the INT_RDA ISR, or a delay in main's while loop, then timing for timer0 is messed up by a factor of about 18 or 20.
Here's the code. I tried to strip out everything that wasn't needed, but it's still sort of long. Basically, I just have the RTCC ISR turning on and off a LED. You're probably saying "don't put a delay in an ISR you dummy!" ... I know, I'm not looking for code guidance, just trying to understand why the delay is affecting the timing, especially when INT_RDA isn't even turned on! What's more interesting is that if *either* delay (in INT_RDA or main) is commented out, then the timing works correctly. Very weird!
| Code: |
#include <18f2620.h>
#device ADC=10 // use 10 bit ADC reading
#fuses HS,WDT256,NOMCLR,NOWDT,NOPROTECT,NOBROWNOUT,BORV21,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=115200, xmit=PIN_C6, rcv=PIN_C7, errors)
#int_rda
void serial_isr() {
delay_ms(100); // comment this out, and timing for timer0 works correctly
}
/* !!!!!!!! LED functions, defines, and variables !!!!!!!! */
#define SLOW_FLASH 1 // transition every second
#define NO_FLASH 0
#define INTS_PER_SECOND 76 // (20000000/(4*256*256))
#define BLUE_LED_PIN PIN_C4
void blue_LED_on(int1);
void toggle_blue_LED();
void check_LEDs(int);
// Number of interrupts left before a second has elapsed
BYTE int_count1;
// variables to store current state of LED
int1 blue_LED;
int blue_flashrate;
#int_rtcc
void clock_isr() {
if(--int_count1==0) {
check_LEDs(SLOW_FLASH);
int_count1=INTS_PER_SECOND;
}
}
/* !!!!!!!! END LED functions, defines, and variables !!!!!!!! */
void main() {
setup_adc( ADC_CLOCK_INTERNAL );
setup_adc_ports( ALL_ANALOG );
enable_interrupts(INT_RTCC);
enable_interrupts(GLOBAL);
/* setup counter parameters */
int_count1=INTS_PER_SECOND;
setup_timer_0( RTCC_INTERNAL | RTCC_8_BIT | RTCC_DIV_256);
set_timer0(0);
/* end setup on counter parameters */
blue_LED = FALSE;
blue_LED_on(FALSE);
blue_flashrate = SLOW_FLASH;
setup_wdt(WDT_ON); // WDT on in software
while(1) {
printf("Hi\r\n");
// delay_ms(500); // comment this out, and timing for timer0 works correctly
restart_wdt();
}
}
/********************* Functions **************************/
void check_LEDs(int rate) {
if(blue_flashrate == rate) {
toggle_blue_LED();
}
}
void blue_LED_on(int1 on) {
if(on) output_low(BLUE_LED_PIN);
else output_high(BLUE_LED_PIN);
}
void toggle_blue_LED() {
blue_LED = !blue_LED;
blue_LED_on(blue_LED);
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Feb 23, 2009 5:26 pm |
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If you have both delay_ms() statements in your program, you'll get a
"re-entrancy" warning message. To fix that, you can create another
instance of the delay library code by adding the line shown in bold below
just above main():
| Quote: | #use delay(clock=20000000)
void main() { |
Then the interrupt routine will have it's own dedicated delay routine,
and the main code will another it's own routine. Their won't be any
re-entrancy issues and the compiler won't disable interrupts while the
delay_ms() statement in main() is running. |
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dyeatman
Joined: 06 Sep 2003
Posts: 1923
Location: Norman, OK
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| Posted: Mon Feb 23, 2009 6:02 pm |
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Also, if the #int_rda is enabled you will have another
problem. Without a getc() in the interrupt routine to clear
the interrupt, the interrupt will not be cleared and it will be
called repeatedly which will cause the program to stay in the
#int_rda delay_ms() almost continously. |
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