Re: RS232 Full Duplex to Half Duplex

From: Tauno Voipio (
Date: 03/25/05

  • Next message: Paul Burke: "Re: Understanding DMA"
    Date: Fri, 25 Mar 2005 08:21:31 GMT
    > Well I am not an expert on rs232 communication, but I was told by my
    > professer that in half duplex rs232 there was only 1 wire between the
    > two devices. What I am trying to do is control a device that works at
    > 57600 baud rate but in Half Duplex mode. But when I was studying the
    > diagrams for the device I am trying to control it has both a Tx and Rx
    > wire. If anyone could point me in the direction of a good rs232 serial
    > communication protocol document I would appretiate it.

    That's not correct - the RS-232 standard specifies the 25 pin
    connector between a DTE (Data terminal Equipment, a computer or
    terminal) and a DCE (Data Communication Equipment, a modem). The
    spec contains, among a lot of control lines, separate transmit
    and receive lines (even another pair for reverse channel).

    If your RS-232 means the common misuse meaning in fact asynchronous
    serial byte-by-byte transfer, then the single data line configuration
    is possible. The connection is often called a party line: all receivers
    are connected directly to the line and all transmitters are connected
    via enabling/disabling gates to the line. The enable logic may be
    internal to the tranmit interface chip or a separate chip.

    It's up to you to decide on the connection. You'll need some
    kind of interface chips anyway - the RS-232 standard signal
    levels are not compatible with the processor and UART signals

    If the RS-232 spec is not to be taken too literally, one solution
    is to use RS-485 connection and interface chips (Google for it).
    Please note that you need a couple of resistors to feed the idle
    state to the line when all transmitters are turned off.

    Tauno Voipio
    tauno voipio (at) iki fi

  • Next message: Paul Burke: "Re: Understanding DMA"

    Relevant Pages

    • Re: Changing Node Type
      ... under the network setup wizard I chose OTHER in the "Select Connection ... the ADSL unpowered, and state 2 with it powered up. ... the laptop could ping the desktop but not vice versa. ... communication, as desired, without having to spend time unplugging cables. ...
    • Re: relation between twin primes and Sophie Germain primes
      ... inflict alongside the cafe, if Ghassan more sails the comparison? ... Her communication was ... Faris originates, then Agha lazily lodges a superior tragedy ... for instance while you're campaigning in connection with a evolutionary ...
    • Re: Simple point-to-point communication with an embedded platform and an Android smartphone
      ... Android smartphone. ... streaming connection that must persist "indefinitely". ... I haven't explained all the details about the communication I'd ... storing microcomputer programs on standard audio cassette. ...
    • Re: Yet another thread on the legality of port scanning
      ... > The normal means of communicating on the internet is via IP ... Authorized users are told they are authorized users. ... is an acceptable connection in the absence of explicit permission? ... effective communication of ideas, not random unsolicited ...
    • Re: wireless internet and hacking
      ... First, a primer on how network communication, of any sort, works. ... actual network connection, which may involve a packaging of its own. ...   is trivial and you can even expect people to do it accidentally. ...