need transeivers for system development

[T. Rooks]

Hello,

Please be gentle. This is my first time;) .

I am a retired computer/medical electronics/electromechanical device field engineer.

A friend got me interested in developing an idea he had. It involves having various separate units performing precise high speed operations in a time and security critical network.

I have developed several modules and have them working as intended in a 'hard wired' ring topology configuration. What I now need is to get them converted to wireless using as small packages as possible to get no less than 100 meters range in the outdoors. They must also have an operating temperature range of -50 to +85 C. They will spend most of the time waiting for very short transmissions and will respond with very short transmissions.

I am prepared to develop my own protocols for them to sync up and accept commands/data to and from each other as I already have a rudimentary system doing that task. However I would not mind modules that have embedded 16/32 bit processors if I can get documentation and be able to use Basic or C programming and if it can add an extra level of security with minimal time overhead.

Any and all recommendations, suggestions or ideas will be greatly appreciated and acknowledged.

Thanking all in advance for your help,

Tim

[Brian]

Wow Tim, looks like you have quite a beast to tackle! These don't have the ideal included MCU, but I've just been playing with the nRF24L01+, and they can handle almost all of the protocol for you. A poke around the datasheet will give you a great idea of how useful they will be to you. With two-way payloads, one could easily keep these time-synchronized, and a decent antenna (biquad, perhaps) would increase the range, as well as choosing an open 2.4 GHz channel, but it may require amplification to get your 100 meters. I'm not sure of the true limits of their range, that's up to testing.

I've not done anything of the standard you've described, this is just where I would start out of the gate. Good luck!

-Brian

[T. Rooks]

Brian,

Thank you for your quick response.

The part number you mentioned was indeed one of the reasons I came to this site to post an inquiry. Actually it was the older version of that part that had come up a time or two in my research.

It is indeed a fabulous part and if I had much deeper pockets my search could very well have ended here. In many cases there are whistles and bells all lumped together in the product that do not necessarily fit or even enhance what my design is about.

The process I am about at this time is not so much filling my shopping bag with the best available as it is with finding very good products that I can use in combination and can afford at this time. There is also the problem of new standards and methods that were heretofore unknown to me.

I am a bit curious though as to why the link you provided takes me away to another site entirely. Could you enlighten me a bit about that?

For now I am leaving my query open in hopes of gaining other inputs.

Thanks again for your response,

Tim

[Ole Morten]

Your temperature requirements are pretty wide, and I actually don't think any of our current chips go from -50 to +85 degrees Celsius. The nRF24L01+ comes close at -40 to +85, but that's about it.

However, if you can limit your temperature range to -25 to +75 degrees Celsius, I'd recommend you to look at the nRF51822, which is an improved nRF24L01+ radio plus an ARM Cortex M0 MCU, giving a single-chip solution. The product specification is available here.

If -25 to +75 degrees is too little, but -40 to +85 is sufficient, the nRF24L01+ is our other option. The official specification is here (the one Brian linked to is an old, out-dated version), and as you can see this is a pure transceiver chip, that can be used from any microcontroller with an SPI interface. This has a slightly more limited radio, but should still be usable for your application.

[T. Rooks]

Ole,

Thanks for the info. -25 to +75C will do nicely.

I am giving serious study to the nrf24L01 or actually the newer version. Could you recommend a suitable (25 - 75 C) microcontroller and programming tool for programming everything in Basic

I am having trouble figuring out how to send a broadcast to multiple units at the same time.

The data in the broadcast is a crucial trigger that has to be received simultaneously by multiple remotes.

I was trying to do this with XBee modules even though they did not meet my temperature requirements just so we could put together a demonstration system. One of the three units failed with 8 hours and the two remaining had a .001 failure rate tor Tx/Rcv messages.

Being able to do this will in effect complete what I had developed with all the units hardwired together.

Also are there hobby/developer groups out on the web that you would care to recommend?

Thanks again,

Tim

[Nguyen Hoan Hoang]

The nRF51822 has ARM Cortex-M0 running at 16MHz that you can use without additional MCU. I don't think you can do ring topology with it though. You can get it to do star topology with one acting as Central and the others as Peripheral. It would not be difficult to implement your own protocol by using Buetooth custom service described in NAN-36.