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SDI-12 COMMAND &
RESPONSE PROTOCOL
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.
n
is a single digit integer (0-9) 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.
Upon completion of the measurement, a service request "a<cr><lf>" is sent to the data recorder
indicating the sensor data is ready. The data recorder may wake the sensor with a break and collect
the data anytime after the service request is received or the specified processing time has elapsed.
Example of an 'aM!' Command:
Command
Response
'aM!'
"a0012<cr><lf>"
Subsequent Command
"aD0"
Where:
X.XX
= Current position (stage), in user programmable units
NNNN
= Current position, in raw position counts
Measure Command with CRC
This "Measure" command causes a measurement sequence to be performed with a CRC appended
to the data. 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
"aMC!"
Where:
a
is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
M
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.
n
is a single digit integer (0-9) 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
Upon completion of the measurement, a service request "a<cr><lf>" is sent to the data recorder
indicating the sensor data is ready. The data recorder may wake the sensor with a break and
12
collect the data anytime after the service request is received or the specified processing time has
elapsed.
Time
1 sec
Response
a+X.XX+NNNN<cr><lf>
Response
"atttn<cr><lf>"
Values
Description
2
Return encoder position
Description
Initiate measurement
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