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I2C problem — Parallax Forums

I2C problem

CCraigCCraig Posts: 163
edited 2007-06-03 16:18 in General Discussion
This I2C program leaves the SDA line low after a read.

Sorry, you know how it goes, Sunday, only one chip to test with...etc. etc.

Is it a defective 24LC128 holding it low? It messes up the next read command.

My fix: do a HIGH SDA, even with lots of protection (resisters) has me worried even though its the only thing on the bus.

I don't know why the eeprom is not letting go. Ideas? until I can get a new chip to test.

Thanks, Chris
sxb
sxb
24LC128.sxb
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SDAgoodSig.jpg
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SDAhangLow.jpg
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Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-06-03 15:32
    Just to confirm you are using 4.7K pull-ups on both the SDA/SCL lines, correct?

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    Chris Savage
    Parallax Tech Support
  • CCraigCCraig Posts: 163
    edited 2007-06-03 16:08
    Yes I am, Chris.

    That's what makes me wonder if it's a bad eeprom holding it down? I won't have another one for a while to test it. It works fine IF I use "HIGH SDA" after the read. If I don't, the next read or write gets messed up. Got to be the 24LC128 ? It only does it after the read "MEM_OUT" sub.

    Thanks, Chris
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-06-03 16:13
    I would recommend verifying what is holding the line by unplugging the 24LC128 or disconnecting at least that one line at the point where it seems to do this and measure the voltage on the line from the SX.

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    Chris Savage
    Parallax Tech Support
  • CCraigCCraig Posts: 163
    edited 2007-06-03 16:18
    Good idea. I'll do it.

    That will at least tell me what side is doing it.

    Thanks

    nothing like on-line support! on a week-end, no less. Thanks
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