YSI Data Scout Advanced - Manual (Page 104)

A P P E N D I X B
SDI-12 COMMUNICATION
SDI-12 is an industry standard serial digital interface bus. The bus was designed to allow compatibility between data collection devices
of various manufacturers. SDI-12 is a single master multi drop bus and command protocol. As many as 10 sensors can be connected
to the bus as a time. Each sensor is pre-assigned a unique address (0-9, a-z, or A-Z). Each Level Scout is factory-set to address 0
(zero).
This appendix documents some of the SDI-12 commands supported by the Level Scout transducer. All commands listed alphabetically
have the following information:
Command a 1-3 letter abbreviation (operation code for the command)
Function a description of the command
Syntax a complete rendering of the command’s structure
Sensor Response a description of the response(s) returned by the Level Scout
Some commands require another special Get Data command (“D0”) to follow them (immediately or after a delay of “ttt” seconds, as
indicated by a parameter in the “main” response). Also, some command responses generate a “main” response, which is followed “ttt”
seconds later by a second response: called the Service Request response. In both cases, a standalone colon (:) will indicate this required
following relationship between two commands and two responses.
To avoid unnecessary repetition of frequently-used parameter descriptions in the table entries, each occurrence of a simple “a” item
always represents the address of the sensor. Also, “ttt” represents a common parameter of a “main” response: time in seconds until
data will be ready to read with a following “D0” command. All responses end with a non-printable <CR><LF> character pair, which
is not shown in the table.
Command Function Syntax Sensor Response
I Identify Sensor aI! A13—YSI---AS2---hhh-ssssss-vvv
13 Supports SDI Version 1.3
commands
YSI Manufacturer
AS2 Model Number
hhh Hardware revision
ssssss Serial Number
vvv Software revision
D0 Get Data aD0!
Note:
This command is only issued
after a Start Measurement
command (various “M[v]” or
“C[v]“). It should not be
issued until measurement time
(returned in response) has
expired or extra Service
Request response has been
received after a Start Non-
Concurrent Measurement
(various “M[v]”) command is
issued.
Example: 0D0! (Send Get Data
command to sensor “0)) av or apu
avu or aputu or avv or avvvv
p is ± pressure value.
t is ± temperature value.
“v” is other non-specific value
“u” is + units indicator
Example: 0-10.23-0
If previous measurement command was
“M” or “C” above example response
would be “avu” form and would indicate
that the water level of sensor “0” is a
10.23 feet.
Note: If address is returned alone with
no data and unit values, this indicates
that there is no data available. Either a
Start Measurement command was not
issued, the command was aborted by
sending a new command before the
measurement time expired, or an
expected Service Request response was
not yet received.
M or M0 Start non concurrent
pressure measurement aM!
: attt2
:
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