Watchdog periodic wakeup

[jimbostlawrence]

Hi all,

The solution to this is probably very straightforward but I'm trying to use the watchdog as a wakeup timer based on the roughly 4ms 'no postscaler (=1)' setting...

The inc file is as follows:

NOLIST
 ifdef PM_USED
 LIST
 "Error: PM does not support this device. Use MPASM."
 NOLIST
 else
 LIST
 LIST p = 18F26J53, r = dec, w = -311, f = inhx32
 INCLUDE "P18F26J53.INC" ; MPASM Header
 CONFIG XINST = OFF
 CONFIG PLLDIV = 2; 
 CONFIG WDTPS = 16;
 CONFIG WDTEN = ON
 CONFIG OSC = HSPLL; INTOSCPLL 
CONFIG ADCSEL = BIT12
 CONFIG RTCOSC = T1OSCREF 
CONFIG IESO = OFF
 CONFIG CFGPLLEN = ON
 CONFIG CPUDIV = OSC1
 CONFIG CLKOEC = OFF
 CONFIG SOSCSEL = LOW
 CONFIG DSBOREN = OFF
 NOLIST
 endif
 LIST
 BLOCK_SIZE EQU 64

...whilst the PBP program is:

Include "modedefs.bas"

DEFINE OSC 24                                         

ancon0 = %11111111
ancon1 = %00011111

intcon = 0
intcon2 = %11110101
intcon3 = %00000000

blue_led                var portb.2
red_led                 var portb.1

ADCON0.0                =   0
ADCON1                  =   15

trisa                   =   %00000000
trisb                   =   %10100000
trisc                   =   %00000000

pmdis0 = %11111101
pmdis1 = %11111101
pmdis2 = %11111111
pmdis3 = %11111111
WDTCON.0 = 1

main:
high red_led
low blue_led
sleep 5
@ nop
high blue_led
low red_led
sleep 5
@ nop
goto main

Essentially, I just want the board to go to sleep minimising current but wakeup every 4 ms or so, switch and LED, or do something, and go back to sleep.

But... the LED switching frequency seems to be a function of the SLEEP value as opposed to the WDT postscaler value. I assumed that once the device was asleep, that was it fo rthe SLEEP command and when it woke up, it was past that, through the NOP command and onto the next line of code... and hence the value of the SLEEP command was meaningless....
i.e. if I set the sleep values to SLEEP 1, the LED switching frequency is far quicker than for SLEEP 5...

Please help...

Regards

Jimbo

[pedja089]

Use @ SLEEP
PBP SLEEP will override your wdt settings.

[jimbostlawrence]

ARGHHHHHHHHHHHHH it was THAT simple?!

ok, now I'm smiling!

Many thanks... I think that answers other questions that have been bubbling away in the back of my mind with other projects!

And thank you for being so quick! I literally went to make a coffee, returned and refreshed and there it was.

[pedja089]

Glad I could help.