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soonc
Joined: 03 Dec 2013
Posts: 215
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| PIC18F47K42 and WDT |
 Posted: Sat Mar 21, 2020 11:28 am |
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Using the PIC18F47K42 I would like to use the WDT selectively.
So I figured I need to set the FUSE
and the first thing in main() switch off the WDT as example below.
| Code: |
#include <18F47K42.h>
#FUSES WDT
void main()
{
setup_wdt( WDT_OFF ); // does not stop the WDT it resets the cpu
rest of code here....
}
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However the code just does a reset about once per second.
How to selectively enable / disable the WDT ?
Here is code I would like to use:
| Code: |
#include <18F47K42.h>
#fuse WDT
#use delay(clock = 12000000, crystal = 12000000)
void main()
{
int32 g_n32WDTCounter=0;
setup_wdt( WDT_OFF );
enable_interrupts(GLOBAL);
/////////////////////////////////////////////////////////////////////
// eventually using DS32KHz as SOSC as a more accurate clk for the WDT
setup_wdt( WDT_ON | WDT_1S | WDT_WINDOW_100_PERCENT | WDT_CLK_31000);
// at some point in future code call this....
do{
restart_wdt();
sleep( SLEEP_FULL );
delay_cycles(1);// nop after sleep
output_toggle( PIN_B3 ); // for scope monitoring
g_n32WDTCounter++;
}while( g_n32WDTCounter < 30 ); // about 30 seconds
setup_wdt( WDT_OFF );
reset_cpu();
}
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What is it I'm not understanding about the WDT ! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Mar 21, 2020 12:52 pm |
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You have to turn off the hardware enable, to let the software
enable/disable work. Example:
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Ttelmah
Joined: 11 Mar 2010
Posts: 19504
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| Posted: Sat Mar 21, 2020 1:02 pm |
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Key thing is the line in the data sheet (registers 5-5), where the options
that enable the watchdog in the fuses all have the note: 'SWDTEN is
ignored'.
So as PCM_Programmer says if you want software control of the WDT,
you can't turn it on in tghe fuses.... |
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soonc
Joined: 03 Dec 2013
Posts: 215
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| Thanks for the help |
| Posted: Sat Mar 21, 2020 4:54 pm |
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Thanks for the help.
I've tried several combinations of FUSES but still can make it work. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Mar 21, 2020 5:35 pm |
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I assume you mean "still can not" make it work ?
Post your current test program. |
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Sat Mar 21, 2020 6:30 pm |
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just a comment...
you should not enable interrupts without 'handlers' ( ISRs)...
your program enables the 'global', so if the 'wizard' has enabled specific interrupts, unknown to you... they WILL cause you random problems....I don't know if you use the 'wizard' or other 'helper' butone programmer's idea of defaults won't ever be what you KNOW the 'defaults' need to be.... |
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soonc
Joined: 03 Dec 2013
Posts: 215
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| Posted: Sat Mar 21, 2020 7:50 pm |
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| PCM programmer wrote: | I assume you mean "still can not" make it work ?
Post your current test program. |
Thanks PCM P I meant cannot make it work... But I did and it's going ok now...
Thanks for the help. |
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temtronic
Joined: 01 Jul 2010
Posts: 9225
Location: Greensville,Ontario
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| Posted: Sun Mar 22, 2020 2:38 pm |
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I have to wonder why an 'accurate' WDT is needed ?
WDTis only enabled after final program is made and then 'timeout' is usual computed as 1.2 - 2 x a 'failsafe' value.
Say main() does everything and updates a 'flag' about 5 second interval. WDT could be set to 7-10 seconds.
There's probably no need for subsecond accuracy. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19504
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| Posted: Mon Mar 23, 2020 2:26 am |
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What he is trying to do, is reasonable. The way to use the WDT, with
SOSC, is:
| Code: |
#define WDT_SOSC 0x2000
setup_wdt( WDT_ON | WDT_1S | WDT_WINDOW_100_PERCENT | WDT_SOSC);
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By default the standard settings only support operation off the 31K, or
31K25 internal clock.
This correctly puts 0x27 into the 0x395C register, to select SOSC.
There are always individual settings that get 'missed' like this, and
you just have to create the extra settings when this happens. |
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