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Odd SX failure... — Parallax Forums

Odd SX failure...

peterjpeterj Posts: 24
edited 2005-05-30 06:41 in General Discussion
I haven't been playing with the SX recently, but one of my breadboards has been running a little LED sequencer for the past few months -- just as a little curiosity sitting on my desk. When I sat down this morning it was "stuck" with just one LED lit. I hit reset pin and a few LEDs flickered. It it it again and then everything went blank. Additional power cyclings, resets, and wiggling of components all had no effect.

Then I decided to try to re-program it, and after doing so it is working just fine again.

Any ideas as to what might have happened here?

-p.

Comments

  • ForrestForrest Posts: 1,341
    edited 2005-05-29 16:01
    I hope you are using current limiting resistors in series with the LED's. Without them and you'll either cook the LED or reset the power supply because it's drawing too much current.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-05-29 16:06
    Hello,

    ·· Is this being powered by battery or Wall supply?· The only time I have ever had a system lock up was when there was a brownout in the power that day.



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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • pjvpjv Posts: 1,903
    edited 2005-05-29 19:53
    Hi Peter;

    It is quite rare for this to happen, but clearly not impossible. It can be attributed to any number of possibilities, including alpha particles, and once it happens, there is no history log to track the occurrence of events.

    It is for reasons like this why the designers included a watchdog timer; and I presume that for your little curiosity program you had not activated that. If you had, then I would become quite concerned.

    Peter (pjv)
  • peterjpeterj Posts: 24
    edited 2005-05-30 04:25
    Come to think of it, there *was* a power glitch the previous evening and I am running from a wall-wart.

    While I can understand the SX locking up as a result of power glitch, it should recover from a reset, or at the very worst case by power-cycling. This I would completely understand. It was the fact that the program area alone seems to have gotten trashed that has me concerned. And after a re-programming, it seems to be working just fine.

    -p.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-05-30 05:24
    ·· Power glitches (brownouts) can affect different electronics devices in different ways.· We once had a triple brown-out in the area I lived in.· The power glitched 3 times in a row.· A person down the road from me had her entire computer fried.· Everything in it was charred and black, and the whole thing stunk of burnt electronics.· So how did a brown-out (usually a temporary interruption) cause the computer to go up in smoke?· The power supply...The constant on/off on the switching power supply put it into an invalid state, probably stopped the oscillator, but shorted the main power rails right to the board.

    ·· It's entirely possible that something similar happened to you, except that maybe an option fuse or memory locations were affected.· Perhaps the oscillator?· Which reminds me, were you using the internal osc?




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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Guenther DaubachGuenther Daubach Posts: 1,321
    edited 2005-05-30 06:41
    Peter,

    I know it is too late this time but in case you come across the same effect in the future, it might be an idea to use the SX-Key "Run - Device" option, and then do a verify before re-programming the chip. This might tell you if and what data has changed in the EEPROM.

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    Greetings from Germany,

    G
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