I wanted to connect FEZ Cobra with FEZ Domino using XBee. I bought XBee shields from GHI. Those shields are designed to work with Digi XBee modules (former MaxStream). First problem is that Digi offers a whole variety of modules which are divided into:
Point to Point & Point to Multipoint (P2P & P2M)
ZigBee/Mesh
I have no knowledge about industrial wireless technologies but as I read I found out that the first kind (P2P and P2M) uses 802.15.4 protocol and second kind (ZigBee/Mesh) is the actual ZigBee technology that is build on top of 802.15.4. For my first demo project I wanted only to connect two devices so I have chosen:
XB24-ACI-001
This is a P2P/P2M module with on-chip antenna. I set up my demo by connecting each module to each board. FEZ Domino was programmed to increment int counter and send its value every second, and FEZ Cobra was programmed to receive the data and display it on the screen. Both boards were laying next to each other. I have encountered two problems:
Each board was connected to my PC with its own USB cable. This caused some data loss (Cobra displayed e.g. 10, 12, 16, 19). After I unplugged FEZ Domino from PC and plugged it into FEZ Cobra USB Host port everything works with no problem. Is this some GROUND issue ?
I have performed a range test by connecting the FEZ Domino board to a laptop and trying to determine how far can I go with it (line of sight). I wasn’t able to reach more than 5 m because nothing was being displayed on Cobra! Datasheet tells me that this module should be able to work within 30 m range indoors !
I would be grateful for some tips from those that have some XBee experience
I did read the example on microframeworkprojects.com before i started playing of course. I’ve made an USB <-> TTL converter and I’m able to configure my modules using XCTU. I’ve updated the firmware and restored the default values on them. Then I changed the channel and PID numbers from default values. Also I’ve changed the baud rate to 57600 kbps.
Funny thing. I’ve changed the power source of Domino from laptop USB to a 12V power adapter. It seems that the range has gotten better a bit. Maybe if i change Cobra power source to 6V adapter the result will be better… ?
My xbee modules run 112500 baud and have high range.
one thing you might want to check out is the transmit power.
You can check this in X-ctu (attachment)
Which model do you use by the way?
Please note that some countries have a limited power level (for example Europe and Japan) as found in the datasheet on the digi website. By law you may not over exceed this limit, it’s your choice to do this or not(!)
Also, changing to a different channel might work.
My test setup was a cobra and domino. The cobra was inside on USB power and the domino was in the backyard with a regulated power supply (6v)]
You mean 115200 ? I don’t think setting serial baud rate has anything to do with wireless range. This only determins how fast can you transmit data to be send over air by the module (correct me if I’m wrong). What type of antenna are you using?
I use Digi XBee XB24-ACI-001
Did it, the same for PID
The thing that bothers mi is the power supply issue. If i have both device connected to each other the wireless communication is flawless. When i unplug Domino from Cobra and plug in a power adapter, i lose the communication. When i plug Domino back to Cobra, communication comes back
Well, in my case it did. I could receive valid data (sometimes not) for a certain range. After cranking up the baud rate I got valid data over long distances.
Wired. Both modules.
Have you tried to check if this also works with 2 separate power supplies and a common ground?
I’m thinking about writing my master thesis using FEZ components and ZigBee technology and I think this title can come in handy. Can i ask where you bught it ? It seems that it has not been released yet
You can buy the book on safari online , I bought it "Online Access: $17.99"
Then You can download the PDF File of early version.
I will also include the FEZ and .NET MF part in my PhD thesis.
