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Thread: Connecting external digital pin to MCU's pin.

  1. 2nd March 2009 08:29 PM #1
    allegro
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    Default Connecting external digital pin to MCU's pin.

    I would like to connect a digital pin from a chip called CS5463
    http://www.cirrus.com/en/pubs/proDat.../CS5463_F2.pdf
    to my MCU.
    The MCU input pin is defined as tristate.

    My question is how can i be sure that the digital pin of the CS5463 will be able to change from '1' logic to '0' logic, meaning that it would be "strong" enough to change logic states?

    What should i look for in each datasheet?

    Thanks.
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  2. 2nd March 2009 08:38 PM #2
    blueroomelectronics
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    Which microcontroller do you plan on connecting it to?
    Bill
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  3. 2nd March 2009 09:46 PM #3
    allegro
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    ADUC812, can you help me please?
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  4. 2nd March 2009 09:55 PM #4
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    They both have SPI so as long as they're running from the same voltage they should be compatible.
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  5. 3rd March 2009 04:34 AM #5
    allegro
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    But the two mentioned pins that i want to connect together, the CS5463 digital output pin and the MCU digital input pin are not SPI peripherals.
    So is it stll ok?
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  6. 3rd March 2009 04:46 AM #6
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    Do they share the same power source(i.e the same ground connection) ? If so, then you can connect them together. Then 5V will be read as 5V.

    If they do not share the same ground, 5V on the CS5463 maybe 12V on your MCU or any arbitary voltage that can damage your MCU.
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  7. 3rd March 2009 04:48 AM #7
    futz
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    Quote Originally Posted by allegro View Post
    But the two mentioned pins that i want to connect together, the CS5463 digital output pin and the MCU digital input pin are not SPI peripherals.
    So is it still ok?
    As Bill says, as long as they're similar voltage it will probably be fine. Don't connect a 5V output to a 3.3V input pin though, unless the datasheet says it is 5V tolerant.

    You can connect 3.3V outputs to 5V chip inputs though. I do it routinely. In a recent project I have my 3.3V ARM7 board outputting a servo pulse-train that I connect to an input pin on a 5V PIC 12F683. Works just fine.
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