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485 to 232 adapter — Parallax Forums

485 to 232 adapter

Eric REric R Posts: 225
edited 2006-01-26 15:49 in General Discussion
I see a lot of RS232 to 485 converters out there but I have not seen much for 485 back to 232.
Whats the best way to bring in a 485 signal and convert it back to 232 for input into the BS2?

I am looking to take 232 further than the recommended 50 foot.

Comments

  • Robert KubichekRobert Kubichek Posts: 343
    edited 2006-01-21 21:15
    Eric R said...
    I see a lot of RS232 to 485 converters out there but I have not seen much for 485 back to 232.
    Whats the best way to bring in a 485 signal and convert it back to 232 for input into the BS2?



    I am looking to take 232 further than the recommended 50 foot.

    idea.gif Put 2 back to back.... turn.gif


    I have done that using cat 5 cable for long runs... yeah.gif

    Bob N9LVU scool.gif
  • John R.John R. Posts: 1,376
    edited 2006-01-21 23:15
    Running RS-232 for more than 50 feet can be done, _usually_ without problems. If the environment is noisy, you may have problems, and at extreme lenghts, your speed will be limited.

    I have successfully run over 150 feet at 9600 baud in a shop environment.

    Note: This is at "full" RS-232 voltage, not the TTL levels direct from a stamp.

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    John R.

    8 + 8 = 10
  • Eric REric R Posts: 225
    edited 2006-01-21 23:41
    Robert Kubichek said...

    idea.gif Put 2 back to back.... turn.gif


    I have done that using cat 5 cable for long runs... yeah.gif

    Bob N9LVU scool.gif
    I was looking at my adapter and I see a TD (A), TD (B), GND, GND and +12v on the terminal strip

    It looks like this is a transmit only.· Any recommendations on a bi-directional adapter?
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-01-21 23:50
    www.bb-elec.com
    · They have a few 232-485 converters (either to the other, bi-directional).· You can likely buy what you need for less than making it, assuming your time is worth money and you really haven't many parts.·

    · If you have the skill and inclination, then MAXIM makes a 232-485 converter IC (it's also the one used in the B&B units), they also make TTL-485 converters [noparse][[/noparse] www.maxim-ic.com ]· You can look them up on their site and go over to DigiKey or Jameco to purchase them.

    · Someone may pop up and post that it's not necessary to "convert" at all.
  • Eric REric R Posts: 225
    edited 2006-01-21 23:57
    PJ Allen said...

    · Someone may pop up and post that it's not necessary to "convert" at all.
    Thanks, I will look into that.

    I should explain, not only will I be taking it past the recommended 50 foot but I would like to use the multidrop party line features where I can use the addressing.

    At any rate, this is something I have not played with and wouldn't hurt to learn about.
  • nick bernardnick bernard Posts: 329
    edited 2006-01-26 14:05
    pop-up!

    is 485-232 neccessary? i interface a 485 network with my projects with a single ic; the SN65LBC182P is available at digikey. but that is strictly asynchronous w/o flow control.

    as for ttl serial. i've tx'd 9600-8-n-1 from stamp to stamp 150ft in a noisy environment and a 500ft spool.

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    engineer, fireman, bowler, father, WoW addict [noparse];)[/noparse]
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-01-26 15:49
    Nick is right.

    485 to TTL and straight in to any of the 16 I/O pins. If you have to invert, I believe that can be specified in the software.
    Using the BasicStamps RS232 progaming port is a bit of a nusance as it has ECHO in the receive. Do you really want or need that?

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
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