Basic SDI-12 Interface Parameters
Up to five devices/commands can be accessed using the SDI-12 interface. There are three parameters for each device/
command: Enable, Device Address, Device Command. For more information, refer to the SDI-12 Technical Notes.
Enable. Instructs the DXM Controller device to activate or deactivate the SDI-12 device. Write a 1 to enable, and write a 0
to disable. The factory default for device 1 is enabled; devices 2 through 5 are disabled.
Device Address. Each SDI-12 device must have a unique device address. This parameter is the ASCII code for the device
address. Valid device addresses are
0–9
and
a–z
that map to ASCII codes
48–57
and
97–122
, respectively. The factory
default addresses are:
•
SDI-12 Device 0 uses ASCII code 48
•
SDI-12 Device 1 uses ASCII code 49
•
SDI-12 Device 2 uses ASCII code 50
•
SDI-12 Device 3 uses ASCII code 51
•
SDI-12 Device 4 uses ASCII code 52
Device Command The SDI-12 interface supports "M!" or "C!" commands. Use the Device Command parameter to define
which command to use for this device. The factory default is "M!" commands for all devices (value of 10 in the Modbus
register).
Supported M! Commands
SDI-12 Command
Register Value
xM!
0 or 10
xM1!
11
xM2!
12
xM3!
13
xM4!
14
xM5!
15
xM6!
16
xM7!
17
xM8!
18
xM9!
19
Supported C! Commands
SDI-12 Command
Register Value
xC!
1 or 20
xC1!
21
xC2!
22
xC3!
23
xC4!
24
xC5!
25
xC6!
26
xC7!
27
xC8!
28
xC9!
29
The Modbus configuration registers are listed. All registers are defined as Modbus holding registers. The factory default
values are shown in parentheses. All values are in decimal, unless noted otherwise.
Device/CMD Configuration
Registers (Default Value)
Enable
Device Address
Device Command
SDI-12 Device/CMD 1
1751 (1)
11001 (48) 7
11002 (10)
SDI-12 Device/CMD 2
1701 (0)
11201 (49)
11202 (10)
SDI-12 Device/CMD 3
1651 (0)
11401 (50)
11402 (10)
SDI-12 Device/CMD 4
1601 (0)
11601 (51)
11602 (10)
SDI-12 Device/CMD 5
1551 (0)
11801 (52)
11802 (10)
SDI-12 Device Result Registers
The result registers store all information received from the SDI-12 devices.
The registers are 16-bit registers and require two registers to store a 32-bit value. The factory default configuration
defines the result registers as 32-bit registers, floating point format, and the first nine result registers are enabled for use.
A host system reads the SDI-12 device data from these registers.
Result Registers
Register 1
Register 2
Register 3
Register 4
Register 5
Register 6
SDI-12 Device/CMD 1 Result Upper
11101
11103
11105
11107
11109
11111
7 The default device addresses 48 through 52 are in ASCII.
DXM100-Bx Wireless Controller Instruction Manual
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