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One Rx with Multiple Tx's — Parallax Forums

One Rx with Multiple Tx's

FalconFalcon Posts: 191
edited 2011-09-12 06:25 in Accessories
I'm trying to make some wireless window alarm sensors. The required range is < 50 ft. I initially planned to use some 433 MHz Tx's and Rx's from http://www.rentron.com/remote_control/TWS-434.htm. I have some of their TWS/RWS units working now with Holtek Encoders and Decoders in a mock-up on my bench. I spoke to Bruce Reynolds the other day about this. He said a typical configuration uses one Tx with multiple Rx's. The Holtek addressing lets that one Tx "connect" to the various Rx's. However, the reverse is not necessarily possible. Multiple Tx's sending to one Rx, as my configuration requires, is not too reliable as the signals from the different Tx's will step on each other causing some inputs to be missed.

What are my options for multiple Tx's communicating with one Rx?

I see some Nordic units at Sparkfun but I don't see many examples af them in use with the BS2 family.

I also see the X-Bee units but they might be overkill for sending just one bit of data indicating whether a window is open or closed.

Are there any possabilities that I may have missed?

Thanks,

falcon

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-09-10 17:59
    Have you seen Ron's code for using the Nordic modules with a BS2?

    You probably want to send more than one bit of information. In my panic button project, each transceiver had an ID number. Each unit would wait a certain about of time after receiving a transmission before resending the information. Each unit was only allowed to transmit during its own time window. These time windows were based on each units ID. This way the different units wouldn't all transmit at once.

    There are some relatively inexpensive Nordic modules available. (I forget which thread has the link to the cheap Nordic modules.) I think the Nordic modules cost about $7 each (from ebay).

    Duane
  • john_sjohn_s Posts: 369
    edited 2011-09-11 00:38
    I'd say try this http://www.ckuehnel.ch/PDF/bs2pCommnFeat.pdf and read about S.N.A.P protocol starting from page 260.

    That's what I used over 10 years ago when communicating multiple LINX 433MHz and 418MHz radio modules to a single base station.
    It was just a proof of concept demo and used TxRx in every single unit that communicated sensor data to a single RxTx base station.
  • FalconFalcon Posts: 191
    edited 2011-09-11 14:47
    Duane,
    I looked at the Code by Ron and I have to say it was over my head. If I could have 5 Tx's each transmit just one of those 5 button codes, I'd be able to distinguish individual Tx's. Would the various Tx's interfere with each other. In other words, in a one Tx/One Rx situation, what happens if you press several buttons at one time. I'll have to take a closer look and see if I can work it into my project.

    john_s,
    I downloaded that document. I'll have to find some time to read it.

    I appreciate the replies.

    falcon
  • Mike GMike G Posts: 2,702
    edited 2011-09-12 06:25
    Falcon instead of guessing what wireless device to use, why not simulate the wireless network using hardwired connections. It would be a lot easier to test your Rx/Tx code and find a scheme that works for your project. The final step is matching a wireless unit to your requirements.
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