AT commands
Networking and security commands
XBee/XBee-PRO S2C 802.15.4 RF Module User Guide
72
Parameter range
0 - 6
Default
0
RN (Random Delay Slots)
Sets or displays the minimum value of the back-off exponent in the CSMA-CA algorithm. The Carrier
Sense Multiple Access - Collision Avoidance (CSMA-CA) algorithm was engineered for collision
avoidance(random delays are inserted to prevent data loss caused by data collisions.
If
RN
= 0, there is no delay between a request to transmit and the first iteration of CSMA-CA.
Unlike CSMA-CD, which reacts to network transmissions after collisions have been detected, CSMA-CA
acts to prevent data collisions before they occur. As soon as a device receives a packet that is to be
transmitted, it checks if the channel is clear (no other device is transmitting). If the channel is clear,
the packet is sent over-the-air. If the channel is not clear, the device waits for a randomly selected
period of time, then checks again to see if the channel is clear. After a time, the process ends and the
data is lost.
Parameter range
0 - 3 (exponent)
Default
0
ND (Network Discovery)
Discovers and reports all devices found in the network. For each discovered device, the following
information is returned after a jittered time delay:
Node discover response when issued in Command mode:
MY<CR> (2 bytes) (always 0xFFFE)
SH<CR> (4 bytes)
SL<CR> (4 bytes)
DB<CR> (Contains the detected signal strength of the response in negative dBm units)
NI <CR> (variable, 0-20 bytes plus 0x00 character)
PARENT_NETWORK ADDRESS<CR> (2 bytes)
DEVICE_TYPE<CR> (1 byte:
0
= Coordinator,
1
= Router,
2
= End Device)
STATUS<CR> (1 byte: reserved)
PROFILE_ID<CR> (2 bytes)
MANUFACTURER_ID<CR> (2 bytes)
DIGI DEVICE TYPE<CR> (4 bytes. Optionally included based on
NO
settings.)
RSSI OF LAST HOP<CR> (1 byte. Optionally included based on
NO
settings.)
A second carriage return will indicate the network discovery timeout (
NT
) has expired.
When operating in API mode and a Network Discovery is issued as a 0x08 or 0x09 frame, the response
will contain binary data except for the
NI
string in the following format:
2 bytes for Short Source Address
4 bytes for Upper Long Address
