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Need a LONG serial cable for the SXKey — Parallax Forums

Need a LONG serial cable for the SXKey

cbmeekscbmeeks Posts: 634
edited 2005-09-25 00:54 in General Discussion
My work bench is now behind my computer desk (instead of being crammed onto one desk).

This is working out well but I now want to run a long serial cable to the workbench. It will have to run up the wall, over the ceiling, and down the wall to the bench. So, I guestimate 25-35 feet.

Is this even possible? Can you still program the key with a long cable like that? If so, where would I get one? I assume the cable is straight-through?

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Comments

  • John CoutureJohn Couture Posts: 370
    edited 2005-09-20 01:32
    DB9 to DB9, 25ft, $17 http://www.cablestogo.com/product_list.asp?cat_id=919&engine=adwords!654&keyword=(db9+extension)

    There are also WIRELESS serial cable extenders (saves you climbing through the attic)

    There are some fancy devices that run over CAT5 up to 3300 ft. http://www.minicom.com/kvm_232.htm

    The only limitation is your pocketbook.

    I did google search on RS-232 Extender.

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    John J. Couture

    San Diego Miramar College
  • cbmeekscbmeeks Posts: 634
    edited 2005-09-20 01:35
    thanks!

    But am I correct? Straight through?

    Cause I could probably make one using CAT5

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  • John CoutureJohn Couture Posts: 370
    edited 2005-09-20 03:13
    Hey another resource is Jan Axelson's book "Serial Port Complete" (ISBN 0965081923).

    His book states that RS-232 length can work up to 50-100 feet (pg 6 & pg 118). Yes, straight through because you use a straight through cable when you connect using a short cable. In other words you do not use a null modem.

    As far as using Cat 5 which is actually four twisted pairs. Hmmm. I don't see why not. I don't think an RS-232 cable is shielded. I would just avoid things like flourescent fixtures which have transformers and ionized tubes.

    Also there are RS-232 to RS-485 converters which can communicate in the 4000 foot range.

    I'm not aware of any schematic on the SX-Key but if one is not public, Gunther Daubach or Jon Williams can probably tell you how many wires in the DB-9 connector will be needed. I think the buzzword is experiment here.

    Heck, you probably have an extra RS-232 cable laying around. Cut it in half, put the cat 5 in the middle and connect it up. It's either going to work or not. Could be done in less time that it took both of us to write about it. (grin).

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    John J. Couture

    San Diego Miramar College
  • Robert KubichekRobert Kubichek Posts: 343
    edited 2005-09-20 03:23
    cbmeeks said...
    thanks!

    But am I correct? Straight through?

    Cause I could probably make one using CAT5

    Get, or wire up a 50 ft cat5 cable, and get a pair of db9 to rj45 adapters.
    The idea of rs232 to rs485 is better, and will resist noise/interfearence better.

    Bob N9LVU scool.gif
  • cbmeekscbmeeks Posts: 634
    edited 2005-09-20 12:16
    thanks guys

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  • Guenther DaubachGuenther Daubach Posts: 1,321
    edited 2005-09-20 15:53
    cbmeeks,

    yes, it is straight through. See the attached picture for an example how you could extend the serial cable length. Using flat cable removes quite a bit of mechanical stress from the SX-Key, so I also have prepared a "short extender", better called a "stress reliever".

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    Greetings from Germany,

    G
    Serial Cable.jpg
    833 x 1343 - 47K
  • PJMontyPJMonty Posts: 983
    edited 2005-09-20 18:00
    John,
    John Couture said...
    Hey another resource is Jan Axelson's book "Serial Port Complete" (ISBN 0965081923).

    His book states that RS-232...

    Just for clarity, Jan Axelson is a woman, not a man.

      Thanks, PeterM
  • John CoutureJohn Couture Posts: 370
    edited 2005-09-20 18:24
    Funny. You know I looked on the "about the author" on the book and such trying to determine the gender and finally just had to take a guess. Nonetheless, HER book and her series of books are EXCELLENT!

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    John J. Couture

    San Diego Miramar College
  • PJMontyPJMonty Posts: 983
    edited 2005-09-20 19:59
    John,

    Yes, they are.
      Thanks, PeterM
  • John CoutureJohn Couture Posts: 370
    edited 2005-09-21 23:11
    Gunther,

    You mentioned your cable above provides mechanical strain relief for the SX-Key. Have you found any distance limitations FROM the SX-KEY TO the SX? In other words, what if one were to make a little 4 conductor cable that plugged into the key and into the MCU assembly.

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    John J. Couture

    San Diego Miramar College
  • PJMontyPJMonty Posts: 983
    edited 2005-09-22 06:58
    John,

    Some people have successfully extended leads from the sxKey to the chip being programmed and debugged. However, it is not recommended as the clock that drives the SX chip is on those leads. If you're working on a project with a 50 or 75 MHz clock, that means you'll be sending that high speed signal across your extensions. If it works - great. If not, don't be surprised.

    Extending the serial cable and using a ribbon cable for strain relief is a safe approach.
      Thanks, PeterM
  • Guenther DaubachGuenther Daubach Posts: 1,321
    edited 2005-09-22 08:31
    John,

    I agree with Peter - extending the four-pin ISP side can be critical when you use the SX-Key as clock generator while debugging, or using the IDE's "Run-Run", or "Run-Clock" options. When you use the SX-Key for programming only, extending the ISP side is less critical because the communication between the SX-Key and the SX is performed at a much lower speed.

    I never tried to extend the ISP side of the SK-Key, therefore, my opinion is theoretical only. Mybe, you just give it a try, and share your experience with the group.

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    Greetings from Germany,

    G
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-09-22 09:43
    Personally, I can't seem to operate without the computer and the SX project on the same table.
    {I suppose that I just think I have to tinker with connections and work with the robot.}

    But for those who do or must, a couple of rs-232 to rs-485 adapters would nicely remove the distance limitations.

    I am not sure, but maybe USB is an improvement too.

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    G. Herzog in Taiwan

    Post Edited (Kramer) : 9/23/2005 9:12:48 AM GMT
  • PJMontyPJMonty Posts: 983
    edited 2005-09-22 19:35
    G. Herzog,

    No, USB has a rip roaring distance limitation of 16 whole feet. RS-232 can go much farther (~50 feet or so) and RS-422 or RS-485 will take you into the thousands of feet range.
      Thanks, PeterM
  • cbmeekscbmeeks Posts: 634
    edited 2005-09-22 20:01
    But then again, USB2.0 is 480 mb/S. How fast is RS232? 19kb/S??

    So, there's your distance problem. smile.gif

    Thanks for all of your suggestions guys.

    Now here's another. Which of the 9 pins are actually used in the SXKey? Cat 5 only has 8 but surely not all 9 are needed for the SXKey.

    thanks

    cbmeeks

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  • John CoutureJohn Couture Posts: 370
    edited 2005-09-23 04:42
    The top of the SX key has 5 connections. Just use a continuity tester?

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    John J. Couture

    San Diego Miramar College
  • Guenther DaubachGuenther Daubach Posts: 1,321
    edited 2005-09-23 08:10
    All you need are pins 2, 3, and 5 of the 9 pins.

    The baud rate for communication between the PC and the SX-Key is 57.6 kBaud.

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    Greetings from Germany,

    G
  • cbmeekscbmeeks Posts: 634
    edited 2005-09-25 00:54
    G
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