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Xbee/Zigbee embedded radio devices.

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Patrick

Mon May 27 2013, 11:20PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

deos anyone have experience with these?

im planning on using the Xbee PRO ZB, 63mW transmit power 250kbps, 34 US$. My purpose is to link through UART or SPI across a transparent radio duplex a flying drone to a simple base station, (a STM32F4 to a F1 or Basic stamp, or PIC) range should be 100 feet high certainty in a Wifi/blutooth/brushed motor saturated enviroment

link: (because i cant find the PDF),

Can anyone advise me on these so-called indoor/outdoor range estimates of 300ft Indoor/urban and 10,000 ft line of sight/outdoor? are these estimates for 63mW credible? or just guess work on corporate advertisments?

it does use Direct sequence spred spectrum... (DSSS) if that helps fidelity of low power radio transmission...

Carbon_Rod

Tue May 28 2013, 02:01AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Xbee is not Xbee pro, and ranges vary with antennas.
Also, most people only buy modules with a FCC stamped transceiver and on-board certified antenna.
Most kits require programming the interface context, and are not truly ad-hoc to configure.

Simply put, a short-range bluetooth rs232 adapter is usually an order of magnitude cheaper to deploy.

Cheers,
Rod

2Spoons

Tue May 28 2013, 02:03AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

I've used the Xbee pro extensively, and I was reasonably impressed with the range. I was getting reception over 300m, behind a small hill. I never hit the LOS limit (not enough room at ground level). This was about 5 years ago when the claims were more like 50m indoors and 300m LOS outdoors. Best range is with the 1/4 wave whip antenna. Don't forget : 250kbps is the transmission symbol rate, not the data throughput, which will be somewhat lower ( thanks to protocol overheads, interference, etc)

These are really good modules, I found them ridiculously easy to set up.
For reference, my use was streaming gps data off 8-10 greyhounds at a race track. That gives you some idea of the environment I was working in.

The downside of those cheap chinese bluetooth modules is the generally terrible documentation. So while they cost less $, they can easily cost more time. Specs can be dubious too.

Patrick

Tue May 28 2013, 04:09AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

spoon, carbon,

do i need a $400 developement kit?
why does the serial data rate get listed as high as 1mbps?
I was planning on using the whip antenna.

i did expect some moderate programming to be nessacary, and it not to be plug an play.

Carbon_Rod

Tue May 28 2013, 06:02AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

If you have time, there are the WiFly RN-171-XV which actually support TCP instead of orphan standards:

$34.95 from Microchip:

Note the WPA2 setup is easier if you have a good router around..

Cheers,
Rod

Patrick

Tue May 28 2013, 03:39PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

there is no way i can use wifi, it just wont be reliable, ive seen the other teams panic and try to deploy wireless-N routers right in the arena.

and i dont think radio capable SPI is a "orphan" standard. In fact, there could be huge potential for corporations, garage tinkerers and students. ..

2Spoons

Tue May 28 2013, 11:17PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

No, you don't need the development kit. Just rig up a pcb with an Xbee and an RS232 interface. You may benefit from building a better base station by getting the Xbee with the antenna connector and attaching a decent wifi antenna - depends on the range you need.

1Mbps is the rate at which the serial interface talks to the micro on the xbee, not the module to module throughput. Look at page 64 of the Xbee manual. Throughput in a zigbee network is listed as 35kbps best case.

You might want to look at some of the point to point modules for better throughput - the zigbee protocol layer is designed for building robust, low data rate networks around a mesh topology - not really what you are doing. One of the 802.15.4 modules would be better, though I can't find the throughput figures for that, pretty sure thats what I was using (names have changed). Don't forget : Zigbee sits on top of the 802.15.4 protocol layer, and so adds more overhead.

Carbon_Rod

Wed May 29 2013, 05:19AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

@Patric, remember when we discussed why UDP was better for some things...

The modules are cheap enough that you may want to buy both to evaluate.

There are "paired" ZigBee Pro kits for around $90 to $250. Some people like the perceived simplicity, and they are usually wrong.

...Its probably even easier to condition a pigeon to fetch with servo controlled French-fries...
what do the rules state about cybernetic organisms...?

tobias

Wed May 29 2013, 01:36PM

Registered Member #1956 Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172

Patrick, I am working on a electric plane/quadcopter/car/boat controller system just for some fun learning. I chose the rfm22b for TX/RX. OpenLRS uses it, so it is proven =)

We already tested our own brushless motor driver and the idea is to integrate everything in one modular pcb =)

Take a look at this module (if you haven't done already) and let me know what you think!

Patrick

Wed May 29 2013, 03:21PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

i have to admit this does look simple and more like what I want :

"RFM22B-S2 SMD Wireless Transceiver" so input of the TX and output of the RX is more direct while still using SPI? right tobias? this is the direction carbon whats me to look at.

spark fun is selling them at 12 US$, so that's good.

and yes electro-shock and French fries for a pigeon would be easier...

tobias did you use SPI?

the Xbee wqith zigbee overhead does transmit farther in a urban environment...

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