Operating Instructions
Combined Wind Sensor ARCO SDI-12
(14582) ARCO SDI-12
Operating Instructions
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SDI-12 Interface
The communication using SDI-12 protocol via SDI-12 interface is based on the ‘SDI-12 A Serial-Digital Interface
Standard for Microprocessor-Based Sensors, Version 1.4, 2017’. The ARCO SDI-12 can be used in bus mode
parallel to other ARCO SDI-12.
The combined wind sensor behaves like two individual bus participants with their own addresses for wind
speed and wind direction.
The following subset of SDI-12 commands were implemented into the ARCO SDI-12.
For more information on the SDI-12 protocol, please refer to the standard documentation mentioned above or the
website www.SDI-12.org.
Implemented SDI-12 commands:
Command
Function
Answer of the sensor
a!
Acknowledge Active
a<CR><LF>
aI!
Send Identification
allccccccccmmmmmmvvvxx...xx<CR><LF>
aAb!
Change Address
b<CR><LF>
aM!
Start Measurement
atttn<CR><LF>
aMC!
Start Measurement and Request CRC atttn<CR><LF>
aC!
Start Concurrent Measurement
atttnn<CR><LF>
aCC!
Start Concurrent Measurement and
Request CRC checksum
atttnn<CR><LF>
aD0!
Send Data (Buffer 0)
a<data<CR><LF>
a<data><CRC><CR><LF>
aV!
Start Verification
atttn<CR><LF>
aX!
Resetting the Addresses
a<CR><LF>
a = address of the respective sensor;
Standard sensor address: Wind speed = 0; Wind direction = 1
SDI-12 commands always start with the address of the appropriate sensor. Therefore all other sensors on the
same bus will ignore these commands. SDI-12 commands end with ‘
!
’. All answers from sensors start with its
address, too, but end with the ASCII characters ‘Carriage Return’
<CR>
and ‘Line Feed’
<LF>
.
The SDI-12 protocol is based on the ASCII character set. The baud rate of the SDI-12 protocol is 1200 Bd and
has the byte frame format:
1 start bit
7 data bits (least significant bit transmitted first)
1 parity bit (even parity)
1 stop bit.
Acknowledge Active - a!
This command ensures that the sensor responds to requests. Basically it asks the sensor to confirm that it is
connected to the bus.
The sensor returns its address and
<CR><LF>
.
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