Rssi Indicators; Device Discovery; Network Discovery - Digi XBee ZigBee S2D User Manual

Device discovery

The configuration steps to send data to the loopback cluster ID depend on the serial port mode as determined by
the AP command.
Transparent Mode
To send data to the loopback cluster ID on the data endpoint of a remote device, set the CI command value to
0x12. The SE and DE commands should be set to 0xE8 (default value). The DH and DL commands should be set to
the address of the remote (0 for the coordinator, or the 64-bit address of the remote). After exiting command
mode, any received serial characters will be transmitted to the remote device, and returned to the sender.
API Mode
Send an Explicit Addressing ZigBee Command API frame (0x11) using 0x12 as the cluster ID and 0xE8 as the
source and destination endpoint. Data packets received by the remote will be echoed back to the sender.

RSSI indicators

It is possible to measure the received signal strength on a device using the DB command. DB returns the RSSI
value (measured in –dBm) of the last received packet. However, this number can be misleading. The DB value
only indicates the received signal strength of the last hop. If a transmission spans multiple hops, the DB value
provides no indication of the overall transmission path, or the quality of the worst link – it only indicates the
quality of the last link and should be used sparingly.
The DB value can be determined in hardware using the RSSI/PWM module pin (pin 6). If the RSSI PWM
functionality is enabled (P0 command), when the module receives data, the RSSI PWM is set to a value based on
the RSSI of the received packet. (Again, this value only indicates the quality of the last hop.) This pin could
potentially be connected to an LED to indicate if the link is stable or not.
Device discovery

Network discovery

The network discovery command can be used to discover all Digi modules that have joined a network. Issuing the
ND command sends a broadcast node discovery command throughout the network. All devices that receive the
command will send a response that includes the device's addressing information, node identifier string (see NI
command), and other relevant information. This command is useful for generating a list of all module addresses
in a network.
When a device receives the node discovery command, it waits a random time before sending its own response.
The maximum time delay is set on the ND sender with the NT command. The ND originator includes its NT setting
XBee/XBee-PRO ZigBee RF Modules User Guide 92