1. Home
  2. Electronics Design
  3. ZigBee and alternatives - low power radio links

ZigBee and alternatives - low power radio links

I'm looking for an inexpensive way to poll a device from about 200 feet outdoor, line of sight. USA-only, no FCC license needed, etc...

We need to exchange about 50 characters or so back in forth, a couple times in a session. Data timing is NOT critical. If more than one device is present, we need to know that, avoid data collission, and be able to talk to each device individually. We do not need a network.

ZigBee looks interesting, and many modules seem to be avaialble. Does anyone here have experience with these modules? Will they fit the bill? Are there other off-the-shelf approaches, or ones that we can design-in?

Our device has enough spare microprocessor horsepower to drive the logic signalling, etc... My request here is concerned with the RF interfacing to the devices. It will be a piece of field testing equipment talking wireless to devices, and there is some possibility (slight) of more than one device being present within 200 feet (+/-).

If recommending ZigBee (or ???), is there a royalty fee involved? Do we have to join some group?? If such costs aren't exhorbitant, I wouldn't think that would be a factor on this project.

Appreciate in advance any good URL's resources, etc...

Thanks!!

-mpm

Reply to
mpm
Loading thread data ...

formatting link

The XBee modules are dead easy to work with, relatively cheap, fully licensed, and the newer models (linked above) claim 400 ft ranges. There's also a "Pro" model for slightly more $$ that's spec'd out to one mile. Just be a bit cautious about mixing nodes from different generations/versions.

--
Rich Webb     Norfolk, VA
Reply to
Rich Webb

It's likely overkill for what you need, but take a look at these:

formatting link

You do *not* want to do ZigBee yourself! It's a mess.

The above has a microcontroller that I understand is available for applications (written in Python).

You might also try RFM for wireless modules.

Reply to
keithw86

Thanks Rich, this looks perfect. Have you worked with these modules before?

Do you (or anyone here) know if you can issue a broadcast message and have all units in range respond, or MUST you know in advance the address of each module prior to starting a session with it??

-mpm

Reply to
mpm

I played with them (er ah "evaluated suitability for an application") a couple of years ago.

I *think* that each module "discovers" others in range and can be queried for the IDs of accessible modules. I'll have to dig out the kit (if it's here and not at the office) and play^H^H^H^H evaluate them some more to refresh my memory, though.

--
Rich Webb     Norfolk, VA
Reply to
Rich Webb

Thanks !!! I would really appreciate it!

Reply to
mpm

Short answer: yes. Longer version: Set the modules to a selected channel (one of 15 for XBee and one of 12 for XBee Pro) and PAN (personal area network) ID (one of 65536). Have the base station periodically send a "who's there?" message and/or have individual nodes send an "I'm here" message to the broadcast address. The application firmware would sort out the replies and go on from there.

Modules have a factory-set 64-bit address or can optionally use an end-user selected 16-bit address. One address (0x000000000000FFFF) is reserved as the broadcast address in both the 64- and 16-bit address spaces.

Messages to broadcast addresses are not automatically ack'd by the firmware. Point-to-point traffic (i.e., to a specific address) requires an ack at the transport layer and will retry several times, if needed, transparent to the application layer.

This is from the manual and modules with V 1.06 firmware from back in

2005/6 but I wouldn't expect newer releases to be less capable. 
--
Rich Webb     Norfolk, VA
Reply to
Rich Webb

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.