Chapter Four
Troubleshooting
Man_455U-D Rev 3.05
Page
63
influences, including atmospheric conditions, changing landscape, degradation of antennas or
co-axial cable, low battery voltage etc. Fade margin is an indication of how far a radio path
can deteriorate before reliable communication becomes unreliable.
When using this feature, the current value of the received signal strength is displayed in dBm
(decibels referenced to 1 mW). This value is updated every half second. To check the radio
path between two units, Use the AT#B command to check the signal strength between two
modules. Next, measure the background noise by selecting the AT&T5 command and reading
the value from the terminal. For reliable operation, with a safe margin for changes in the radio
path, the received signal should be better than the following margins:
Radio Baud Rate
Margin above Noise
Minimum Value (dBm)
9600
10
-95
4800
10
-105
AT\S Radio Statistics
The AT\S command returns useful statistics on radio operation, which modems can be heard
from a particular modem, and how good the signal strength is from each modem.
AT\S
Radio Statistics
\S
Display stats including last received signal strength from all module
addresses – 1 – 127 (only modules that have been received are
displayed).
1 RSSI: -98dBm Rx: 95 Fwd: 0 Err: 72 Last: 0d03h19m18s
Stats are: Last Received signal strength, Number of Messages Received
from this address, Number of messages Forwarded from this address,
and Number of received messages with errors from this address. Also
indicates the time since last received a message from this address.
\Snn
Display Stats for remote number nn only
4.4.3 On-line diagnostics
Diagnostic values may be read by the 455U Configuration program or by a host device, using AT
commands. These values include the radio signal strength of the last message received (ATS9?)
and the reason for the communication link resetting in Acknowledged mode (ATS12?) - refer
Appendix C.
Diagnostic registers are:
S-Register
Meaning
S9
Radio signal strength of last radio message received
S12
Reason for radio link resetting in Acknowledged mode - refer App C for codes.
