Vaisala WXT520 - Manual (Page 153)

Appendix A ______________________________________________________________ Networking
VAISALA______________________________________________________________________ 151
RS-485 Serial Interface
Wiring
1. Make the RS-485 wiring of WXT520 as described in Chapter 5,
Wiring and Power Management, on page 43 .
2. In the data logger end, combine the "Data +" wires of each
WXT520 to the logger "Data +" wire. Connect the "Data-" wires of
each WXT520 to the logger "Data -" wire.
Communication Protocol
Set the communication protocol to ASCII polled (with or without CRC)
or NMEA query. When using NMEA query, the wind message should
be set to XDR (aWU,N=T).
ASCII, Polled
WXT520s on the bus shall be assigned with different addresses. (for
example: aXU,A=0,1,2, ... ).
Example (a bus with three WXT520s):
WXT520 #1 communication settings:
0XU,A=0,M=P,C=3,I=0,B=19200,D=8,P=N,S=1,L=25
WXT520 #2 communication settings:
1XU,A=1,M=P,C=3,I=0,B=19200,D=8,P=N,S=1,L=25
WXT520 #3 communication settings:
2XU,A=2,M=P,C=3,I=0,B=19200,D=8,P=N,S=1,L=25
NOTE No matter which communication protocol, ASCII polled or NMEA
query is chosen, the error messaging parameter of the supervisor
message must be disactivated with aSU,S=N for each WXT520 on the
bus in order to prevent the units responding to the commands not
assigned to them.