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What is a rs232 transceiver? — Parallax Forums

What is a rs232 transceiver?

computer guycomputer guy Posts: 1,113
edited 2008-03-29 02:18 in General Discussion
I have a Lantronix Matchport b/g connected to the propplug however this didn't work so I phoned Lantronix and they told me I need to have an rs232 transceiver between the Matchport b/g and the propplug.

What is an rs232 transceiver and why do I need to use one?


Thank you smile.gif

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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-03-28 23:00
    The PropPlug takes in USB and puts out a logic signal that goes between ground (logic 0/low) and 3.3V (logic 1/high).

    Strictly speaking, RS232 requires a +3 to +12V signal for logic 0 and a -3 to -12V signal for logic 1. The RS232 transceiver converts one set of voltages to the other and provides some protection for the logic devices and some signal conditioning to reduce noise on the RS232 line.

    For a description of RS232, do a web search for "wiki RS232".

    Regarding the Lantronix Matchport b/g. Their own website says that their serial ports are 3.3V compatible, so you should be able to connect them to the PropPlug and maybe Lantronix misunderstood what the PropPlug does. To be safe, you should use a small value resistor (like 1K) between the PropPlug and the Matchport in each signal line. This protects both devices if you should connect them improperly. If you always connect an output to an input, you shouldn't need the resistor. If you accidently connect an output to an output, you could damage either or both devices if the two outputs go to opposite logic states. The resistor protects against this.

    Post Edited (Mike Green) : 3/28/2008 11:07:39 PM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2008-03-28 23:02
    The matchport b/g is a 3.3v logic level device. So I shouldn't need a transceiver, right?

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  • Mike GreenMike Green Posts: 23,101
    edited 2008-03-28 23:06
    Yes. See my edited comments.
  • computer guycomputer guy Posts: 1,113
    edited 2008-03-28 23:08
    Thank you Mike smile.gif

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  • stevenmess2004stevenmess2004 Posts: 1,102
    edited 2008-03-29 02:17
    computer guy, do you have a cro? If not you could try the logic analyser that is around for the propeller to check that you are actually getting a signal from the matchport.
  • computer guycomputer guy Posts: 1,113
    edited 2008-03-29 02:18
    Will do. Thank you Steven. smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
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