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jimcbride
Joined: 05 Apr 2006
Posts: 23
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| WDT Sleep() and wakeup |
 Posted: Mon Jun 25, 2007 4:36 pm |
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Greetings,
I seem to remember seeing something written about where the WDT re-enters the code exectution after a wakeup.
If I turn on the WDT, use a sleep() function and have the WDT bring the chip out of sleep, where does the code start at? Does the code restart from zero? Can I tell it where to re-enter the code?
I need to set some output pin states, keep those states while asleep, wake up and set the pin states again with possible new values. I do not want to reset the code to start again at the beggining. This puts glitches in my output pin states. (For instance PIN_A6 is also CLKO, I can see a square wave on PIN_A6 after the WDT wakeup.)
I read that if in sleep mode, the WDT will wake up the chip (not reset) and continue on with code execution.
Am I doing somehting wrong or just not reading the data sheet correctly?
(using PIC18F1220, internal osc @8Mhz) |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Jun 26, 2007 1:00 am |
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| Quote: |
I read that if in sleep mode, the WDT will wake up the chip (not reset)
and continue on with code execution. |
It should do that.
| Quote: | | Where does the code start at? |
At the next instruction after the SLEEP instruction.
| Quote: |
For instance PIN_A6 is also CLKO, I can see a square wave on PIN_A6 after the WDT wakeup. |
The 18F1220 data sheet says this:
| Quote: | 19.3 Two-Speed Start-up
Because the OSCCON register is cleared on Reset
events, the INTOSC (or postscaler) clock source is not
initially available after a Reset event; the INTRC clock
is used directly at its base frequency. |
I don't have any more time to research this right now, but I think either
it may be fixable with fuse settings, or it may not be fixable.
Post a very small test program and show the #fuses statement.
Also post your compiler version.
If possible, post the list of Config bit settings that the compiler puts
at the end of the .LST file. |
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jimcbride
Joined: 05 Apr 2006
Posts: 23
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| Posted: Tue Jun 26, 2007 2:51 pm |
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I will redo a smaller sleep only program and see what that does. I read about the dual speed startup. But since I am already using the internal RC I thought that it would not be a problem. I am not worried about speed waking up or how long it takes so long as the logic levels stay constant. I do have the option of using a different pin if we can't figure this out with the data you requested. Keeping everything on one port does have its advantages though.
More later...
Last edited by jimcbride on Thu Jun 28, 2007 10:10 am; edited 1 time in total |
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jimcbride
Joined: 05 Apr 2006
Posts: 23
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| Posted: Thu Jun 28, 2007 10:08 am |
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From the .LST file.
Configuration Fuses:
Word 1: C900 INTRC FCMEN IESO
Word 2: 150E BROWNOUT WDT BORV20 PUT WDT1024
Word 3: 8000 MCLR
Word 4: 0081 STVREN NODEBUG NOLVP
Word 5: C003 NOCPD NOPROTECT NOCPB
Word 6: E003 NOWRT NOWRTD NOWRTC NOWRTB
Word 7: 4003 NOEBTR NOEBTRB
Compiler version:
3.188
| Code: | #include <18F1220.h>
#device adc=8
#zero_ram
#fuses intrc, WDT1024, BROWNOUT, PUT, NOLVP
#use delay(clock=8000000)
void main()
{
setup_adc(ADC_OFF);
setup_wdt(WDT_OFF);
output_low(pin_a6);//set CLKO low
while(TRUE)
{
output_high(pin_b0);
delay_ms(100);
output_low(pin_b0);
setup_wdt(WDT_On);
sleep();
setup_wdt(WDT_Off);
}
} |
This code will flash an LED. Using a scope, I see that pin_a6 is outputting a 2 MHz signal which is 1/4 the intrc.(8 MHz) This pulse occurs for 100ms. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Thu Jun 28, 2007 10:34 am |
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I'm not really sure to understand what you want to do. You are refering to A6 as CLKO, do you mean here that in some situations you want to use this pin for outputting the processor clock?
Check the datasheet for oscillator configurations (chapter 2.1).
With the fuse INTRC you get Fosc / 4 output on RA6 and I/O on RA7.
With the fuse INTRC_IO you can use both RA6 and RA7 for I/O.
My guess is you want the INTRC_IO setting. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jun 28, 2007 11:02 am |
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I had assumed that you were already using INTRC_IO and so that
you must have some really bizarre problem that was undocumented.
But that's not the case. |
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jimcbride
Joined: 05 Apr 2006
Posts: 23
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| Posted: Thu Jun 28, 2007 11:52 am |
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Thank GAWD, I was hoping it was me doing something stupid, (ususally is).
I went back and forth so many times with intrc and intrc_io trying to get int internal osc working that somewhere I got them turned around in my head. I had these two backwards in my head.
Thanks for the help gentlemen. |
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