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I would like to create wireless communication between Microchip PICs for my simple project. It's actually an one way communication but there is one server and more than one client (about 2-4, all client needs to the same number at the same time, so they are identical). I have to push through very few bytes.

Im absolutely beginner with wireless communication, or almost any hardware communication at all. So please help me, what kind of wireless transceiver should I use?

I have some conditions:

  • It must be relatively cheap.
  • It must be easily available.
  • It would be nice if it easy to use.
  • about 10 meter range (at least)

Firstly I found "Serial Bluetooth RF Transceiver Module rs232" but I can't find any info about how to use. (I guess, it's too simple?) And I also don't know is it capable to connect to more clients. And I also saw ZigBee, but I found it a "little" overpowered for my needs. (And also complicated.)

So what kind of wireless transceiver do you recommend me?

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6 Answers 6

The Nordic Semi nRF24L01+ is ideal for that sort of thing, low-cost modules are available on Ebay:

http://cgi.ebay.co.uk/Arduino-NRF24L01-Wireless-Transceiver-Module-2pcs-/280640828189?pt=LH_DefaultDomain_0&hash=item41577f331d

The nRF24L01+ is often used in wireless sensor networks.

An MCU is required. I have a suitable design and test software here. It uses the much more expensive Sparkfun module, I've designed a board for the cheaper modules but haven't had one made for testing.

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I remember you posted about Nordic before. Can you compare them with XBee? –  Federico Russo Jun 26 '11 at 18:43
    
Completely different. The Nordic devices offer: short range, high data rate, low-power, need low-level programming, and low-cost. –  Leon Heller Jun 26 '11 at 19:06

You may want to have a look at Digi XBee. They have both point-to-point and point-to-multipoint solutions. They're easy to use as you simply connect them to your microcontroller via its UART connections; the complete IEEE 802.15.4 implementation is transparent. I found the price OK (something like 18 euro for a point-to-point module, IIRC).

edit
Indoor range up to 30m, but you probably know that this depends very much on the building's construction. Line-of-sight up to 90m. XBee-PRO version: up to 90m and 1.6km resp.

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Do you know how this compares to the Nordic modules @Leon Heller refers to? –  Federico Russo Jun 26 '11 at 18:44
    
@Federico - No, sorry. –  stevenvh Jun 26 '11 at 18:52
    
Thanks for suggestion it seems friendly. Now I'm going to read a lot of about it. http://cgi.ebay.co.uk/XRF-wireless-UART-serial-data-module-XBee-shape-arduino-/‌​320706374372 Is it what you talk about? –  Felician Jun 26 '11 at 19:53
    
@Felician - seems to be a comparable module based on the same chipset(?), but from another manufacturer. The comparison table shows that this one doesn't support IEEE 802.15.4, so I guess it won't do point-to-multipoint. –  stevenvh Jun 26 '11 at 23:59

You might take a look at Microchip's 802.15 radio modules and the MiWi stack that can use them. This kind of radio is intended for low power and relatively low data rate.

Otherwise, your question is too broad to give a meaningful answer.

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Is line of sight enough, perhaps with a transmitter or reflector in the ceiling? If so, you don't get much easier or cheaper than infrared. You can use a common 38kHz demodulating IC for reception, and send using a 38kHz clock (perhaps off a microcontroller timer) and a digital pin. One example of this is the Lego RCX and Power Functions remotes.

Bluetooth is designed for point to point links, not broadcasts like these.

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Felician doesn't say anything about speed requirements, but a network suggests things like handshaking, error correction and other overhead, and then you often want more speed than a 38kHz can deliver. XBee does 250kbps, Nordic even more. OTOH, RC5 (as a typical 38kHz IR protocol) bursts at 562.5bps, on average 123bps. –  stevenvh Jun 28 '11 at 18:02
    
Wow, infrared is a great idea, I like it, currently it could work! (btw I specified the speed reqs, "I have to push through very few bytes". The clients are numeric displays, they need about 20bytes/minute :)) I would accept your answer, but currently I thinking in radiowave. –  Felician Jun 29 '11 at 14:35

You can use pretty much anything for the communication - it all depends on how abstracted you want the system to be.

You could use something like the XBee, which handles the node linking for you and abstracts the communication for you.

Or you could be more ambitious and use a bunch of discrete ISM transceivers (Industrial/Scientific/Medical - refers to the frequency range it works in) and write your own protocol (maybe something along the lines of how I²C works) for the communication. The fact that you have one master and a number of slaves makes it easier to do.

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1  
if you are interesting in using the transceivers I would avoid the trouble of things like writing your own protocol. That's nice if you are interested in the development itself, for instance if it's a project you have to do for college/university. –  Federico Russo Jun 26 '11 at 18:27
    
@Federico Maybe the OP is interested in the development side of things - I know I am ;) - Just throwing ideas into the mix. That's the glory of this site. –  Majenko Jun 26 '11 at 18:29

I sell RFM70 modules (so I might be biased, beware!). These are cheap, but maybe not that easy to use: 3.3V (but 5V-tolerant data pins), 1.28mm pin grid, Chinese-English datasheet, software interface is a bit complex and the explanation in the datasheet 'could be better'. Range ~ 70 m line-of-sight, but 'within one room' is more realistic. I read somewhere that the chip (RF70) is a lot like the Nordic chip.

I am working on a C library with a better explanation of the interface (for now for LPC2148/GCC and 16F887/HiTech-C, which are so different that other chips should be no problem). (update: the library is available from http://www.voti.nl/rfm70 )

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