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Javelin Stamps blowing out — Parallax Forums

Javelin Stamps blowing out

sharmaitsharmait Posts: 15
edited 2005-05-27 10:27 in General Discussion
We have been working with javelin stamps and BOE (with usb cable) for a long time, recently stamps have been blowing out very frequently.

We sent the damaged ones to the parallax technicians and they said that the chips were burned due to overcurrent or overvoltage··on I/O pins caused·by static or user error. What kind of error·is this "user error" ? I cannot cleraly figure out how pgming errors (what else can be user error) can blow out a chip? Shouldn't there be·some check inbuilt·in the harware circuit to prevent something like this ?

Is there any chance·of·overcurrent/voltage·when pins in one program are output and become input instantly when the next program is·downloaded ? Can a clear registry pgm help ?

Any help would be·appreciated.·Quite a few chips are dead this way...any idea why this can be ?

Thanks very much,
Sharmait.·

Comments

  • dandreaedandreae Posts: 1,375
    edited 2005-05-19 16:34
    It is always a good practice to clear the I/O pins before downloading a program that could potentially damage the stamp.· If you have a pin set high in one circuit and is connected to ground in the next ciruit, it will damage it.



    Dave

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    Dave Andreae

    Tech Support
    dandreae@parallax.com
    www.parallax.com

    ·
  • kb2hapkb2hap Posts: 218
    edited 2005-05-19 16:36
    What are you doing with them when they blow?
    what type of external circuits are connected to the pins?

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    DTQ
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-19 21:26
    Yes, it would be helpful to post your circuit. And Dave offers excellent advice: Always clear your IO pins to inputs before connecting another circuit.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • newnapmannewnapman Posts: 4
    edited 2005-05-20 00:55
    What does this mean?
    Dave said...
    It is always a good practice to clear the I/O pins before downloading a program that could potentially damage the stamp. If you have a pin set high in one circuit and is connected to ground in the next ciruit, it will damage it.

    I am using Uarts, I2C ect. If there is a bug in my code, then I'll download the new prog in the middle of running the Javelin, and run the new one... thi is not bad is it? (Same circuit, although, who knows if the Uart-in pin or the I2C pin was high or low.)

    Christian
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-20 11:57
    "Clearing" the IO pins means to reset them to input mode before changing circuitry -- this prevents a pin that was in output mode from being driven into something that would cause a short circuit and burning out.

    You may have a bad device, or are making a programming error that is causing two outputs (one from the Javelin and one from another device) to be connected together and causing a short.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • JavalinJavalin Posts: 892
    edited 2005-05-27 10:27
    I've had similar issues:

    Check your serial connection to the Javalin is as shown in the manual Errata 1.3. (i.e. there's small caps on the ATN and VSS lines)

    Try running your Javalin on a development board, without any connections to the IO pins. This help isolate the issue.

    James
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