I am using three Xbees which communicate with each other. One of them is a coordinator (in broadcast mode) and the other two are the end devices. The Xbee have been programmed using AT commands through X-CTU and are set to talk in the transparent mode. Initially I had only one Xbee as an end device and the data reception was fine. However, when the second Xbee was added, both Xbees still started receiving data but in an interrupted manner (i.e. the incoming data was cutting off and then reconnecting continuously).
I had two high gain antennas (one 20 dbi and one 9 dbi) on the end device Xbees and they were placed closed to each other. Could that be causing the issue? The issue would stop once one of the Xbees was disconnected.
In general, is there a limit on how many Xbee end devices I can connect with a coordinator which is broadcasting?
My understanding is that the co-ordinator Xbee is like a teacher and the end-device Xbees are the students waiting and listening to any broadcasted data.
Considereng that I set the co-ordinator to broadcasting mode, I was hoping that it will talk to any number of end-devices which happen to be in the vicinity of its broadcast and receive the radio waves sent from it.
Any ideas what was causing the problem and how this can be prevented?
Many thanks in advanced
Which XBee modules are you working with? Believe it or not it does make a difference in how the modules function and what could be going on.
I am using a pair of XBee Pro 60mW Wire Antenna - Series 1 (802.15.4). Thats quite interesting. Actually, after a bit of study, I realised that one xbee talks to one other xbee at a time. I read about people coming up with interesting ways of allowing one xbee to communicate with multiple xbees, but one at a time, not simultaneously.
Is there an easy way to get around this or maybe do you think I can just use one Xbee end device and use a wifi module like a WiFly Shield to allow multiple devices to connect to a access point and receive the data.
First off, the 802.15.4 and 802.11 (WIFI) standards are not capable of communicating with each other.
Yes, the XBee 802.15.4 modules and associated IEEE standard are half duplex devices. You can only simulate a full duplex connection if the interface data rate (Baud rate) is at least 1/2 of the throughput (80kbps).
No, the product does not support simultaneous transmitting and receiving of data. It can only send or receive. In order for it to transmit and receive at the same time, it would need to have separate transmitters and receivers with each having their own antennas.
If you want to send data to more than one device at a time, try using the Broadcast address of 0xFFFF or just don’t use the Coordinator and End device functions. That is leave them in their default Peer to peer states. Another option is to configure them in a classic Point to multi-point configuration with the base module in Broadcast mode and the remote units in Unicast mode back to the base.
Another option is to use just the two modules and connect one of them to an RS485 bus. The reason for the RS485 connection is that it allows for multiple devices to share one serial port.
Many many thanks mvut.
In regards to the Wi-Fi, I did not mean the series 1 xbee to directly communicate with the Wi-Fi module. I meant that the transmitter xbee (coordinator) sends data and the receiver xbee (end-device) receives it. Then, the received data is stored say in a buffer on a microcontroller board like Arduino Mega. An xbee module is also connected to the Mega which can become an access point for all other devices like laptops or iPad etc, to connect to it and receive the data. I am not sure whether that is possible or not, yet. Nonetheless, your methods are much easier and less complicated.
I really appreciate your help and will try your solution and will let you know how I go.
The 802.15.4 standard is not one that comes on a PC or laptop. If you want to store the data in a processor and then send it to a device on a network via a 2nd COM port, the XBee WIFI may be a good option for that other connection.