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How to convert RS-485 to RS-422

Discussion in 'General Electronics Discussion' started by ErichP, Feb 27, 2018.

  1. ErichP

    ErichP

    2
    0
    Feb 27, 2018
    Hi guys,

    I have application where we need to send hd-sdi over single mode fiber with RS data about 6km, unit which we are using in this application is 1ch HD-SDI over fiber with reverse rs-485 data. Is there any successful way to convert RS485 to RS 422?
    I found this converter in google search: RS485/RS422 Converter/Repeater
    I am looking for recommendations, or stay away from's.
    I also would be interested in a USB option if available for true portability (something I can throw in my laptop case).
    Any help would be appreciated!
    Thanks,
    E
     
  2. AnalogKid

    AnalogKid

    2,305
    648
    Jun 10, 2015
    485 and 422 are essentially identical hardware protocols with one major exception. 422 allows for only one transmitter on a bus, and it is permanently enabled. 485 allows multiple transmitters; only one at a time can be enabled, and the others are in tri-state (high-impedance) mode, If you are dealing with a dedicated comm link with one transmitter at one end and one receiver at the other, chips for either protocol should perform identically.

    The link you posted is for a 232-to-485/422 converter. That is a very different thing, because the 232 signal voltage levels are quite different. Note that the other end works for both 485 and 422 with no changes of adjustments.

    If 232-485 is what you really are after, I can walk you through it. It basically is 2 chips (although today there probably is a single chip that does both functions), a 232-to-TTL interface and a TTL-to-422/485 interface. Both parts run on +5 V only. The 232 chip uses on-board charge pumps to generate +/-9 V for the 232 signal lines.

    ak
     
    Last edited: Feb 27, 2018
  3. ErichP

    ErichP

    2
    0
    Feb 27, 2018
    thanks for your answer, do you know where I can buy this product 484 to 422 converter?
     
  4. AnalogKid

    AnalogKid

    2,305
    648
    Jun 10, 2015
    As far as I know, there is no such thing. In a single-channel application like yours, RS-422 and RS-485 are identical.

    ak

    ak
     
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