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How quickly can an xbee pair connect (Coordinator always on, end device powers on)?

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I have an application that requires a quick connection upon end device powering on. The coordinator is always on. How long does it theoretically take to establish a connection?

Currently, it seems to take 2-3 seconds, but I suspect it could be faster and would like it to take less than 500ms. Any ideas are much appreciated.

-- more details --
Sleep is disabled on the end device. It simply powers off and on to save energy. There are only 2 nodes: coordinator and end device.
asked Jun 25, 2015 in IEEE 802.15.4 by gwentecch New to the Community (1 point)

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1 Answer

+1 vote
If you use the 802.15.4 XBee modules, the ability to send data from an node that has been off to a Node that is always on and in range can be done within 100ms or considerably less. For that matter, as soon as /.CTS goes active, you can send data. That is generally less than 20ms after a power on occurs.
answered Jun 26, 2015 by mvut Veteran of the Digi Community (15,323 points)
Thank you for your answer.  It is nice to know it is possible.  Currently, I'm trial-and-error trying different configurations on the end device and coordinator to figure out what is causing the delay.  Using the SMT Xbee (part XB24CZ7PIS-004), I use the following configuration once before normal operation.  Does anything jump out as causing the coordinator to forget its child when the end device powers down (or end device to forget its parent)?  I'm guessing that one or both of them are forgetting the other when the end device powers down.

ATRE (factory defaults)
ATCE1 (coordinator enable)
ATID1234 (set ID)
ATSC0800 (set scan channel)
ATDH0 (destination address high)
ATDLFFFF (destination address low)
ATWR (write values to flash)

End Device:
ATRE (factory defaults)
ATID1234 (set ID)
ATSC0800 (set scan channel)
ATSM0 (sleep disable)
ATWR (write values to flash)
Try looking at he PO command.
Even though PO (polling timeout) is default 0 (100ms), I tried setting it to 0 anyway - didn't seem to change things.  Open to other ideas.  Thank you.
The PO command on a ZB module allows you to tell the end device how often it is to poll its parent for data and how often you can send data to its parent.  Setting it to 0 will not do anything. But setting it to a value of 1 will.