Re: Please Recommend Wireless Protocol and How-To/Tutorial

Actually, TCP/IP probably isn't a good example, as what is on the lower

> layers can be entirely different and encoded and error corrected however > you like, as long as the other end brings it back to the same data. Ok, > that's probably a bit picky, but it is true. ;^)

Right, the point I was after is that even though TCP/IP has plenty of its own error correction built-in, it assumes the lower level has a 'reasonable' bit error rate (perhaps 10^4-10^-6) and using it _without_ further encoding (i.e., with simple CW/AM/FM) over the typical radio link will kill it.

I mention this primarily because I've been told that approach has been tried and the progenators apparently surprised at the results... ;-)

Reply to
Joel Kolstad
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"Joel Kolstad" wrote in news: snipped-for-privacy@comcast.com:

Ok, almost totally off topic, but did you see the EDN article about

10GbaseT, 10GBPS over copper? What these guys are doing for error detection/correction must be orders of magnitude over orders of magnitude beyond what I am capable of. To bring it slightly back on topic, I doubt many of those techniques apply to wireless, unless you are looking at spread spectrum. Certainly beyond the OP's request, though.

Jeff.

Reply to
Jeffrey A. Wormsley

Hi, I have had some of my students do such things in the past, I lecture at the University of Ulster (and am a radio amateur)

A fully fledged protocol that is robust has a lot in it

If all you want to do is pass keystrokes, or some application that just demonstrates the technology then it is not too difficult.

My students just used three remote stations and demonstrated switching a relay on and off, sending back their status when asked and sending back temperatures when asked, all very low volume stuff.

The students spent their time getting the modules going, aerial (i.e antenna (sic) ) working and handling a crude master slave protocol.

The only "gotcha" ( unexpected feature 8-) ) was that if receivers and transmittes are close to each other then switching the transmitter on saturates the receiver and the particular modules we used it took over half a second before the receiver could receive anything after the transmitter was switched off.

(the standard fix for this would be to design a little pin diode switch that shorts out the receiver input so it doesn't see a massive signal from the transmitter. Or to use distance to separate tx and rx aerials, there are other fixes...)

The expedient solution was to add a one second delay!

We just used RS232 and the RTS control line to enable the transmitter (AFAIR). Each transmission was a single line of simple text readable ASCII, with a end of line sequence of CKSM> and a start of line sequence of where n is 1,2,3 or the letter 'M' for slaves 1,2 or 3 or the master. I used the bracket symbols so that if you clip a second PC onto the system you can use hyperterminal to monitor traffic, ( also I implemented the first version of this protocol on 8-bit apple microcomputers ][ )

Hope that helps, I may have a machine readbale version of the student's report, but the info above should get you started. I would only email the report to your prof in any case,

Don't forget to tell the group how you get on!

Regards and good luck Ian McCrum, MI5AFL, lecturer in Digital systems Unversity of Ulster. __

Reply to
Ian McCrum MI5AFL

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