Does anyone know how to connect multiple XBee transmitters to communicate with one base? They each have a sensor attached to them and they need to send data to a main XBee receiver. I also need to be able to identify each XBee transmitter as its own so I know what happened to which one.
How do I do this?
Hi iRagDoll,
I do really like the XBee modules, but they can be a little tricky to setup. I'm assuming you know you need to download the X-CTU software at http://www.digi.com/support/productdetl.jsp?pid=3352&osvid=57&s=316&tp=5&tp2=0.
Using this software you will need to setup one node (probably the base) as the coordinator and the others as end devices. This will require that you burn the software to each of them.
You will need to set the destination address to the base.
Are you just running serial through the XBees and receiving it on the other end?
Yes... sorry for the late reply by the way. There will be multiple XBee transmitters with sensors on each that will need to transmit data to one XBee receiver. There will not be any two way communication.
What are you planning to do about synchronization so that one packet isn't sent in the middle of the other one?
Just get a bunch of these: http://www.moderndevice.com/products/jeenode-kit and implement CTP (http://hinrg.cs.jhu.edu/uploads/CS450/ctp.pdf) to get a nice and robust collection tree to sink.
XBEE+arduino is way too expensive and overkill if you just want to measure a few data points and multihop to a base station.
I really do not know about synchronization, Is there a way to solve this problem?
I'm assuming that by 'synchronisation' you mean media access control (MAC). These fall into two main groups, CSMA- and TDMA-based schemes. Then there's the issue of power consumption, low-power listening MACs save energy by putting the entire board into sleep-mode 99% of the time and wake up periodically to exchange data. The problem with this is time synchronisation.
If you don't care too much about energy consumption (i.e. you don't mind swapping out the batteries every two months or so, which is reasonable if you're not deploying your network on top of a mountain or in a tropical forest) just use CSMA (Carrier-sense multiple access - Wikipedia) without low-power listening, or just use no MAC at all.
Think about it, the odds that the messages of two nodes will collide is extremely low when you have only a few nodes and you're sending data once every minute or so. As long as they are not accidentally perfectly synchronised you will have no problems.
The other option you have is porting Contiki to the JeeNode (http://www.sics.se/contiki/). That will give you ipv6/6lowpan and a bunch of other cool things.