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Compact, low BAUD, RF TX/RX plans? — Parallax Forums

Compact, low BAUD, RF TX/RX plans?

Bent CarhoodBent Carhood Posts: 10
edited 2004-12-29 01:05 in BASIC Stamp
Does anyone have any circuits·for a low BAUD (~20)·RF TX/RX·that is very compact and reliable? Size, reliability, and cost·is more important that speed.· I'd like to get some stamps to·talk to each other. I don't·need much bandwidth, so I figured I could get·away with some "made from scratch"·circuits.·More crude the better.·

TIA,

Mike

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2004-12-27 14:00
    For stamp to stamp communication, you can easily use SERIN/SEROUT on a single wire between stamp pins. Put a 220 ohm resistor in the line as a current limit resistor. Can't get much simpler or cheaper than that.

    You may be distance limited -- I haven't done a lab to show what the max distance you can get over just a wire. In any event, for a little bit more you can put RS485 Transciever chips to get 4000' distance between boards.
  • Bent CarhoodBent Carhood Posts: 10
    edited 2004-12-27 14:13
    Thanks, but I'm looking for a wireless solution.
  • allanlane5allanlane5 Posts: 3,815
    edited 2004-12-27 14:19
    Aha, I missed that key 'RF' in there. Wireless, hmm? There are three or four vendors of wireless transciever units which take RS-232 and put it out as RF that work OK with the BS2.

    If you are trying to 'roll-your-own' you may quickly run foul of the FCC interference rules. The nice thing of the off-the-shelf units is they are FCC approved (bandwidth, interference, distance, and RF power limits).

    Which raises the question, "How much distance do you need?"· If you're in the same room, IR communication could be enough.
  • Bent CarhoodBent Carhood Posts: 10
    edited 2004-12-27 15:43
    My goal is to create a wireless peer-to-peer network of stamps in my house. This also brings up the dual channel issue. I need a a seperate RF channel for send and receive.
  • K de JongK de Jong Posts: 154
    edited 2004-12-27 15:47
    Take a look at the website of Sid Weaver, he has some not so expensive transmit and receive units.

    www.hometown.aol.com/newzed/index.htm
  • K de JongK de Jong Posts: 154
    edited 2004-12-27 15:49
    Here is the link again, I hope it works now.

    www.hometown.aol.com/newzed/index.html

    Klaus
  • SPENCESPENCE Posts: 204
    edited 2004-12-27 16:03
    DUAL FREQUENCIES ARE NOT NEEDED UNLESS YOUR APPLICATION IS TIME/SPEED CRITICAL.

    STUDY THE SYNTAX IN THE BOTTOM 32 CHARACTERS IN THE ASCII CODE PROTOCAL. THEY GIVE YOU THE BASICS FOR ONE WAY TURN AROUND TO ALLOUW MANY PEER TO PEER UNITS TO COMMUNICATE ON A SIMPLEX FREQUENCY.

    IE
    THIS IS #5,HALLO #1 ARE YOU THERE
    THIS IS #1, RGR #5 i AM READY FOR TRAFFIC GO AHEAD
    TRAFFIC, ( END OR MORE TO FOLLOW)
    RGR GOT IT
    THATS ALL END OF WORK

    OPEN NOW FOR ANOTHER INITIATE.

    73 SPENCE
    K4KEP
  • SPENCESPENCE Posts: 204
    edited 2004-12-27 16:06
    Mike see my "1200 baud modems" in sandbox forum


    73
    spence
  • Bent CarhoodBent Carhood Posts: 10
    edited 2004-12-29 01:05
    Thanks Spence. I tend to over complicate things. My background is controls systems for process/manufacturing. I had figured out that I was going to need to do some handshaking. It just didn't dawn on me that it would also filter out the transmittions to itself.

    Thanks again.
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