mamouda@web.de wrote:
> 
> I'd like to design a wireless sensor network (20 sensors) using PIC microcontrollers.
> 
> Which PICs do you think is better for that purpose and which wireless technology (Zigbee. WiMi ?)

I have used XBees for several devices, but would like to move over to 
PICs with a Microchip stack at some point to reduce per-unit cost.

My feeling at this point is that ZigBee has a lot of nice features, but 
if you don't need them, the fact that it's a standard is NOT important, 
because no two ZigBee stacks interoperate yet (as I understand it).  So 
it's really no more "standard," at this point, than Microchip's MiWi.

So - my decision tree goes like this:

A. Is short development time far more important than per-unit cost?  Or, 
are you looking to sell the product commercially?  Go with XBee.  (FCC 
approval is a major cost otherwise.)  There are some other similar 
modules that are no worse, but as far as I can tell, not particularly 
better either.

B. If per-unit cost is important, and FCC approval isn't (or you can 
afford it), try Microchip's ZigBee solution.  Their stack is free, but 
you still have to join the "ZigBee Alliance" ($K).

C. Or if you are OK with the subset included in MiWi (<= 1024 nodes, <= 
8 coordinators), use that.

So far, for home use, I have done (A) but lean toward (C) next.

For small commercial products, I would go with (A) since the FCC 
certification process scares me.

Hope that's of some use.
-- 
Timothy J. Weber
http://timothyweber.org
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