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Watchdog

A StuartA Stuart Posts: 2
edited 2006-07-19 03:29 in General Discussion
Hi,
Anyone having any experience or ideas regarding watchdogs ?

I'm using a Dallas DS1232·WD (watchdog)·to reset the Javelin in case it crashes.
Problem is, from the time the WD pulls down and releases the RESET pin to my main() starts to execute, it takes to long.
The WD will time-out and do a new reset before I have a chance to tickle it in·the main loop.

regards,
anders

Comments

  • Peter VerkaikPeter Verkaik Posts: 3,956
    edited 2004-11-19 11:57
    I use an Sx28 for a CF interface (15 I/O), a serial terminal (2 I/O),

    a serial interface to the Javelin (2 I/O) and a watchdog output (1 I/O).

    On power up the programmed watchdog in the SX28 is off until

    explicitly turned on by the javelin. The only 'problem' is then

    reprogramming the javelin, because the watchdog may reset·the

    javelin while it is being programmed. My simple solution to prevent

    that is either a jumper to disconnect the WD output from the javelin

    reset pin, or recycle power just before programming the javelin.

    (I turn on the WD after 10 minutes which is plenty of time to

    reprogram the javelin)

    regards peter
  • Rob v.d. bergRob v.d. berg Posts: 89
    edited 2005-01-23 19:24
    Hi ,

    I have the same experience with the DALLAS DS1232,·The Javelin·is to late to trigger.

    You can use the MAXIM MAX705 to get a watchdog. You must generate pulses within 1.6

    sec on the WDI input, if not·there is a reset on pin 7 (200msec).

    Pin 1 must be connected to pin 8. This works fine.

    Regards Rob.
  • A StuartA Stuart Posts: 2
    edited 2005-01-23 21:13
    Hi,
    Thanks for the the tip. Problem is the MAX705 is twice the price of the DS1232 wich is already a bit expensive I think.
    I've found a Fujitsu chip; MB3773 at a reasonable price. I have not tested it yet. I will be back when I have.

    Regards
    /Anders
  • Rob v.d. bergRob v.d. berg Posts: 89
    edited 2005-01-24 11:53
    Hi Anders,

    The MAX705 was ~€ 4,-· I saw in·the datasheet of the MB3773·that the max·watchdog time is·~·1000msec,·i wonder if this is·enough, my experience is that it must be longer than ~1.2 sec.

    Regards Rob.
  • Peter VerkaikPeter Verkaik Posts: 3,956
    edited 2005-01-24 15:37
    Go for the MAX6301.

    This has an extended mode that extends the normal timeout 500x

    And make sure to connect the watchdog reset output pin via a jumper

    to the javelin reset pin, so you are able to program your javelin by

    removing that jumper.

    regards peter
    pdf
    pdf
    max6301.pdf
    102K
  • GJGJ Posts: 19
    edited 2006-07-19 03:29
    OK, so this is somewhat of a late post, but for anyone else that is looking for a cheap, easy and flexible watchdog timer, check out the TI ucc3946N, you can program the timeout based upon a cap selection.· This is probably the better choice overall.
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