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    Input Interfacing to PIC Microcontroller

    Hai all Now i am designing Annunciation system so i need to interface 42 input signals ( 5 volt inputs) to my PIC IC. So How can i connect this much inputs to PIC Any decoder/ encoder is available ? or any other methods ? Have anybody circuit diagram for the same
    Please Help me...

    Thanks
    Saneesh George

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  2. #2
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    Re: Input Interfacing to PIC Microcontroller

    Microchip I2C Port Expanders interfaced to PIC I2C Bus.


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  3. #3
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    Re: Input Interfacing to PIC Microcontroller

    74hc165 if spi if prefered
    Love me or hate me. All infractions will be ignored.


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    Re: Input Interfacing to PIC Microcontroller

    Hi sangeo,

    the PIC IO-extender offers 16 IOs per package and three can operate on the I2C or SPI bus( http://www.digikey.com/en/articles/t...-based-designs ). If you use the 8 bit wide 74HC165 you need to decode the I2C/SPI bus and select the in series connected six HC165. Than 6x8 bit clock cycles are needed to read out the 48 inputs. In any case you need to think about input protection and make sure that no input is floating(best is to use a pull-up and a resitor in series). Maybe also clamping diodes if you have overvoltage swing on the incoming signals!

    Enjoy your design worl!


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  5. #5
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    Re: Input Interfacing to PIC Microcontroller

    Okk Thanks Mr.HTA , Mr.pic.programmer and Easyrider83

    Now i am learning about to 74165 and its interfacing

    Thanks to all.



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  6. #6
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    Re: Input Interfacing to PIC Microcontroller

    Cypress and NXP have 40 and 60 bit I2C port expanders if you want to go that route.

    40bit:
    PCA9505
    CY8C9540A

    60bit:
    CY8C9560A



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