Telegesis (UK) Limited
TG-ETRXn-UG-01-103
11
User Guide
1.04
ETRX1 and ETRX2
©2008 Telegesis (UK) Ltd
ETRXn User Guide (Rev 1.04)
changes its physical location; the key point is it that moves enough within the area covered by a
PAN to need a new parent. If, for example, the PAN only contains one parent and a number of
end devices (a “star” topology), there is no point in defining the ZEDs as mobile since there is no
other parent to adopt them.
In the Telegesis AT command software each routing device can have up to eight sleepy end
devices and up to eight mobile end devices.
A module becomes a coordinator by issuing AT+EN as described above. Whether a device joins
as a ZigBee Router or sleepy/mobile end device is determined by the settings in S06 at the instant
the device joins a PAN, so if you are currently joined as a router and want to become a mobile end
device you have to complete the following steps:
1. Leave the network
2. Change S06 accordingly
3. Re-join the network
An end device will always keep its radio switched off (unless used) and therefore consume less
power than a router, even when fully awake.
In power levels 0 to 2 (see section 5) by default an end device will poll its parent for new data once
every second via the built-in functionality. This timing can be altered or disabled altogether if
required. Polling takes less than 10ms, so the battery life of end devices can be maximised. Up to
three incoming broadcasts are stored on each parent until overwritten by new broadcasts.
Unicasts can only be stored for as long as the timeout period on the sending device, so when
expecting to receive unicasts you are required to poll at least in the default interval of once every
second.
When sending a unicast from an end device the unit will keep polling for the acknowledgement
until it has been received or the transmission has timed out regardless of the configured polling
interval.
3.3 Network Establishment and Maintenance
3.3.1 AT+EN
– Establish Network
When the local module is not a member of a network, it can initiate a new one and become that
network‟s coordinator. Issuing the “AT+EN” command scans all the available channels, looking for
the one with the lowest energy level; it then generates a random PAN ID, checks to ensure that a
network with this PAN ID does not already exist and then starts a PAN. A unit on which this
command has been executed automatically becomes the network‟s coordinator and remains the
coordinator until it leaves the network using “AT+DASSL”. Neighbouring nodes can now join this
newly established network
using “AT+JN”.
[If you are familiar with EmberNet R1** meshing technology and preferred the old way of picking
the channel and PAN ID manually, there is no need to worry as this is still possible. S-Register 00
holds a 16-bit word in which each bit represents one of the available 802.15.4 channels 11-26.
Setting a bit to 1 enables a channel, and setting a bit to 0 disables it. It is therefore possible to
mask out channels which are known to be noisy in the chosen application environment. Setting
the mask to fifteen 0s and a single 1 will force operation on one radio channel. (The mask can also
be used to block ETRXn transmission on channels that you wish to reserve for other systems that
may not yet be in operation.)]
Register S01 allows you to select a preferred PAN ID. By default this register is set to FFFF, which
causes the coordinator to pick a random PAN ID when establishing a PAN. Any number between
0000 and 3FFF will cause the unit to start a PAN with the specified PAN ID unless that particular