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Interfacing Digital Devices — Parallax Forums

Interfacing Digital Devices

Andrew BriceAndrew Brice Posts: 5
edited 2005-03-13 14:57 in BASIC Stamp
I have a digital temperature module (FE33) which I want to interface to my BS2.

The FE33 has an AA battery powering it. The BS2 is on a BOE.

The FE33 has a digital output pin. How do I connect these two devices together so that I can use SERIN to read the FE33's value?

I have used SEROUT before to control a PAK-V, however the PAK-V did not use a separate power supply from the BS2 so I understood the circuit.

It may be possible to power the FE33 from the BS2's VDD if this is necessary however I have had problems with this.


All advice would be very much appreciated.

Many Thanks

Andrew

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-02-09 13:36
    You need a common ground -- this will allow your signals betwee the two circuits to work.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • Andrew BriceAndrew Brice Posts: 5
    edited 2005-02-09 15:05
    I think I have done this, but still the BS2 is detecting no high pulses from the FE33.

    How should I have set up the circuit for a common ground?

    Andrew
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-09 16:17
    The negative terminal of all power sources should be connected.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-02-09 16:22
    Connect Vss from the BASIC Stamp side of things to the negative side of the battery on the FE33.

    What is the output from the FE33? Do you have a link to tech docs?

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • Andrew BriceAndrew Brice Posts: 5
    edited 2005-02-13 22:15
    Thank you very much for your advice I have connected this up and it is sort-of working.

    I have another problem now though - the 1.5v High signal from the FE33 is not enough to register as High on the BS2 because it is less than 2.5v. I have tried using a transistor to amplify this signal - but because of the diode effect of the transistor is is impossible for the BS2 to read a Low value.

    Can I make a circuit that will amplify the signal using a transistor, or will I have to buy some opto-couplers?

    Andrew
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-14 02:12
    from your mention of the diode drop I'm assuming your using a bipolar transistor, if you use a mosfet you should be able to get a proper high and low value.
  • Andrew BriceAndrew Brice Posts: 5
    edited 2005-03-13 14:57
    I have now solved this problem using an Op-Amp.

    Thanks for your suggestions and advice.

    Andrew
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