ZNET 2.5 performance issue

XBee & XBee Gateway XBee - Zigbee
1

Hi I am developing an wireless sensor network and using xbee 24-B modules.

I am using the “Transparent Operation” (As the documentation explains it is supposed to be just a wire replacement).

My issue is that data flow is too slow.If I replace the xbee modules with a wire to connect micros UARTs, I get the proper data speed.But even if I have placed the xbee cordinator and end device 1cm apart to test it , still the rate of data flow is slow.I have put “GTCCGT” at the end of the data packet to see whether that makes any difference if incase data is buffered but that didnt make any difference either(I use “Packetization Timeout” as 0).When I say slow I mean it is about 20 times slower than the wired connection.I think it is something to do with the configuring xbees (May be xbee cordinator automaticaly scan for other modules after serving one modules,does it automatically do that? By the way I use the default setting except for baudrate,panID and packetization timeout).

I get some odd corrupt packets but that is something I expected in the wireless medium and my application layer program can handle that but I haven’t expected this extreme slow data transfer speed and I have been trying different ways to fix it for weeks without any success.

The deployment date of the project is getting very close so your urgent reply is highly appreciated.

thanks,
MaxD

2

Try setting the RO parameter to a higher value. Setting it to zero means the XBee tries to send each character as an individual RF transmission, which slows things down considerably.

3

Thanks for the reply.Actually RO was initially 3 but later I reduced it to 0 to check whether that would make any difference.So unfortunately that’s not the issue.

4

MaxD,
How come your using Znet? The last version was released 30 months ago. You might be able to get slightly better performance with ZB firmware.

Here are a few suggestions to optimize your modules:
-set each modules PAN id to something other than default (0x234)
-set each modules DH to the other devices SH.
-set each modules DL to the other devices SL.
-set each BD (baud rate) to 7 (115.2k)
-set each D6 to 1 (enable RTS flow control)

It sounds like you’re streaming data between the two. Is that correct? How freqently and how much data are you sending? Are you writing to the serial port many times a second? what kind of throughput rate are you getting? how may other zigbee device do you have on the PAN?