Wireless communication between more than two Microchip PIC microcontrollers

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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 )