I have been playing with nRF24L01+ transceivers controlled by PIC
microcontrollers.
http://www.libstock.com/projects/view/992/nrf24l01-with-pic16f877a-and-no-l=
i
braries

They would probably meet your needs on a clean channel.  I use a small
spectrum analyzer to pick one that isn't too busy. I believe the US limits
it to the first 83 channels.

This transceiver can send packets of up to 32 bytes of data at a time. It
handles checksums and acknowledgments automatically. You can also set the
number and interval for retries. Right now I'm just using it to send
temperature and door status information but people use them for just about
everything. Small modules with PCB antennas or SMA connectors are very chea=
p
also.

It is also easy for the PIC to switch it from a primary transmitter to a
primary receiver or vice versa.

I am using these:
http://www.ebay.com/itm/10Pcs-NRF24L01-2-4GHz-Antenna-Wireless-Transceiver-=
F
or-Microcontroller-EP98-New-/131026249961?pt=3DLH_DefaultDomain_0&hash=3Dit=
em1e8
1c5e8e9
and these:
http://www.ebay.com/itm/111201706929?_trksid=3Dp2060778.m2749.l2649&ssPageN=
ame
=3DSTRK%3AMEBIDX%3AIT

As for checking the distance, I think most such techniques use phase
relationships. Perhaps you could compare the phase of your outbound carrier
to that of the return signal. I've never tried anything like that.

Allen

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of
> Denny Esterline
> Sent: Wednesday, July 30, 2014 1:39 PM
> To: Microcontroller discussion list - Public.
> Subject: [EE] Recommend a wireless module
>=20
> Needed - wireless transceiver module for north american operation. I have
> control over both ends, so most any protocol is reasonably possible
> (Bluetooth, zigbee, wifi, etc) Likely a 16bit micro on both ends.
> Functionally I need bi-directional control and status information on the
> order of 100 bytes a second, desired latency under 50mS.
> Minimum range of 100 feet line of sight. (practical operating range 30-50
> feet)
> Unit cost not too-too critical $50 ea ok, $20 ea better.
> Relatively small, has to fit into a hand held device about the size of a
> DMM.
> Integrated antenna desirable.
> Power requirements not constraining - other parts of the system use 10's
of
> watts, shaving milliwats here somewhat pointless.
> Immediate demand perhaps 100 units, if all goes well, may need to scale u=
p
> to 1000 units a year.
>=20
> (This next bit is the difficult part)
>=20
> I need a way to measure the distance between two operating modules.
> I'm thinking I can get a reasonable approximation from signal strength -
so
> I would need to be able to read signal strength information at least.
> Other option I'm chewing on is time of flight. It's at least theoreticall=
y
> possible to query remote module and measure the time from query to
> response. Any digital signal processing is going to take vastly more time
> than the signal takes to travel, so this may be challenging :-) I have
some
> thoughts, but this would be vastly easier if there were some supporting
> functions in the radio module.
>=20
> -Denny
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist


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