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serial interfacing

Discussion in 'General Electronics Discussion' started by rizvi, Nov 18, 2017.

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  1. rizvi

    rizvi

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    Oct 27, 2017
    hello.
    i would like to be helped in a serial interfacing problem that i am facing.
    i have a ntc thermistor connected to a max 187 analog to digital converter.
    the output of adc is fed to max232 driver ic.
    rs232 wire is used to carry the data from max232 to the usb port of a laptop.
    here is my problem,, i want to read the temperature variation detected by thermistor on pc.
    but i am not able to do that.
    it seems that the hardware circuit that i have on bread board is not feeding anything to pc.
    i have tried writting programs in c as well.
    if you please suggest me the easiest way to adress the above said problem.
    thankyou.

    Screen Shot 2017-11-18 at 8.17.47 PM.png
     
  2. kellys_eye

    kellys_eye

    4,277
    1,146
    Jun 25, 2010
    Coding issue?

    The serial port connections aren't 'usual' for such comms - have you configured correctly for those control lines?
     
  3. rizvi

    rizvi

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    Oct 27, 2017
    i think there are configuration issues.
    since the hardware circuit is giving me expected results.
     
  4. dorke

    dorke

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    Jun 20, 2015
    "it seems that the hardware circuit that i have on bread board is not feeding anything to pc"
    How did you check this?
    Have you used a scope?

    The circuit is taken from Maxim App note 827 ,it should work.

    Consult the datasheet for sequence of operation and timing the device
     
    Last edited: Nov 18, 2017
  5. Minder

    Minder

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    615
    Apr 24, 2015
    Why are you using DSR RTS DTR?
    The TX/TX is 2 & 3
    Nowadays with high speed peripherals, there is no need for hardware handshake, although it pays to jumper them out at the socket, 1-4-6 and 7-8.
    I see that the app note uses abnormal to convention use of the RS232 port.
    Any use of the H.W. handshake lines such as this requires that the receiving program has it enabled.
    M.
     
    Last edited: Nov 18, 2017
  6. dorke

    dorke

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    Jun 20, 2015
    Because the MAX187 doesn't talk "rs232" !
    There are not used as handshake,
    rather they "toggle" the "command" lines of the MAX187 and read, bit by bit ,it's output.
     
  7. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    Still, the receiving PGM would need to have H.W. handshake enabled, as it is rarely used now in RS232 comm's.
    Does a USB RS232 in port or convertor even use it?
    M.
     
  8. dorke

    dorke

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    Jun 20, 2015
    Yes absolutely,it may be easier done in a DOS environment.
    The program (and programmer) needs complete access to all com. port lines...
    And the knowledge of how to do that;)
     
  9. Minder

    Minder

    2,922
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    Apr 24, 2015
    OK so how do they enter a USB (2wire) port on a laptop?
    It has to be achieved via hardware, if at all.
    M.
     
  10. rizvi

    rizvi

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    Oct 27, 2017
    i have used a d9 to usb connector.
     
  11. rizvi

    rizvi

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    Oct 27, 2017
    yes i wrote a program in .cmd but everytime the value it returns is zero.
    i was thinking if there is any other way to access the hardware using pc apart from writing a pgm in .cmd
     
  12. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Mr. rivizi,
    You must have very good karma...;)

    Read and implement this (pages 161 till 181),do report back if it works.
     
    rizvi likes this.
  13. Minder

    Minder

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    615
    Apr 24, 2015
    I still don't see how that is going to work.
    Is it one constructed yourself just to steer the H.S. lines or is it a off-the-shelf RS232/USB convertor?
    As the latter versions have different configurations in them to take care of the H.S. lines.
    M.
     
  14. rizvi

    rizvi

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    Oct 27, 2017
    thankyou loads for that link. it has something of intrest. i will report as i am hopeful that it is going to work :)
     
  15. rizvi

    rizvi

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    Oct 27, 2017
    yes sir it is off the shelf rs232to usb converter, but any ways i am also trying it on pc having a serial port instead of using usb port on laptop.
     
  16. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    The method shown appears to rely on using a standard COM port 9 pin D.
    A RS232/USB convertor generally only operates on the RX/TX lines,
    Probably the only hope of getting it to work is the standard COM port method.
    M.
     
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