If they don't have receivers built into the modules, you're pretty up
a creek without a paddle (well unless you add a receiver to each
module which increases the cost), but you could make your information
protocol have an Sequence number field and randomly adjust the
interval between packets.  Also you can transmit every packet twice
with the same sequence number so the controller doesn't get confused
or think its seen two packets.

if newseq <= curseq dump packet
if newseq > lastseq keep packet

If the chips do have receievers, make the sensors transmit, then if it
doesnt hear an Acknowledge (with unit #) back within X ms then
retransmit.  You could also decide if the information needs to be
retransmitted as is or if you want to wait for an update.

andrew

On 2/11/06, Dumitru Stama <list@mirosat.com> wrote:
>
> Hello guys,
> I want to implement a few wireless sensors in my home and i was
> thinking about using nordic-based modules like the ones sold on
> sparkfun.com. My question is how can i implement a working
> anti-collision communication between the sensors and base station ?
> If three sensors broadcast at the same time then i might have a
> problem. I was thinking about a token sent by the base station to one
> sensor after which it waits a period of time for the feedback and then
> move to the next sensor and so on. Is this a good way of doing things?
> I can also detect if on sensor has been disabled very easy and maybe
> (if it is a security system) to issue some warnings if the problem
> is still there after a few minutes or a few unsuccessful tries.
>
> Dumitru Stama
>
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