Xylem H-340SDI - Manual (Page 17)

H-340SDI
SDI-12 Command and Response Protocol 2-3
Example of a H340SDI "aM!" command:
Command Response Time Values Description
------------- --------------------- ------- -------- -------------------------------
"aM!" "a0015" 1 sec 5 Return current accumulations
Subsequent Command Response
--------------------------- ------------------------------------
"aD0" a+AA.AAA+BB+CC.CCC+DD.DDD+EE.EEE
Where:
AA.AAA = Rainfall accumulation since last measurement (inches of rain)
BB = Number of bucket tips since last measurement (raw count)
CC.CCC = Total accumulation since reset (inches of rain)
DD.DDD = Total accumulation today (inches of rain)
EE.EEE = Total accumulation yesterday (inches of rain)
2.3 Concurrent Measurement Command
This is a new command for the Version 1.2 SDI-12 Specification. A concurrent measurement is one
which occurs while other SDI-12 sensors on the bus are also taking measurements. This command
is similar to the “aM!” command, however, the nn field has an extra digit and the sensor does not
issue a service request when it has completed the measurement. Communicating with other sensors
will NOT abort a concurrent measurement. Data values generated in response to this command are
stored in the sensor's buffer for subsequent collection using "D" commands. The data will be
retained in the sensor until another "M", “C” or "V" command is executed.
Command Response Description
------------------ ---------------------- ------------------------------------
"aC!" "atttnn" Initiate measurement
Where:
a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
C is an upper-case ASCII character
ttt is a three digit integer (000-999) specifying the maximum time, in seconds,
the sensor will take to complete the command and have measurement data
available in its buffer.
nn is a two digit integer (00-99) specifying the number of values that will be
placed in the data buffer. If "n" is zero (0), no data will be available using
subsequent "D" commands.