PROTEUS SDI-12 Integrated Modbus Output Instruction Manual

Proteus Integrated
SDI-12 and MODBUS Output
Operating Manual
V1.1 December 2021

Introduction

In March of 2020, Proteus introduced integrated SDI-12 and RS-422 MODBUS data outputs for the Proteus water quality multiprobe product line. This optional feature replaces the external converter units previously required for those output formats. The new feature is called “Multi-Protocol Interface Board”, or MIB. One adapter cable provides MODBUS output, and a different adapter cable provides SDI-12 output. The MIB is normally built into the Proteus at the time of the unit’s manufacture; it cannot be seen from outside the instrument and does not alter the Proteus’ size or appearance. The photo below shows a Proteus, Underwater Cable, and at the top of the photo, the short SDI-12 Adapter Cable. The SDI-12 master is attached to the three bare wires on one end of the Adapter Cable. The MODBUS Adapter Cable works the same way.

If you wish to retrofit a Proteus with the MIB option, please contact us. If you wish to build your own MODBUS or SDI-12 converter cable, or convert your Underwater Cable into a converter cable, use the wiring diagrams in Appendices One and Two.
Note that Proteus Data Cables (the short cables used for tasks such as calibration) will communicate with a PC or laptop, but do not support MODBUS or SDI-12 operation.

MIB-equipped Proteus can communicate with a PC and other RS-232 devices as usual (this is the “transparent” mode). Most MIB-equipped Proteus’ can be operated with USB power as usual. However, some of the larger Proteus’ and/ or longer cables (>20m cable or P35/P40 with >250mA consumption – Use Battery life Calculator to check) may require the USB Converter’s  12V adapter to communicate with that Proteus. The photo at right shows a “wall wart” that provides 12 volts to the USB Adapter that connects an Underwater Cable or Data Cable to the USB port on a PC or laptop. You can use a 12-volt battery as well.
Note also that early Proteus Data Cables will work only in transparent mode; the Modbus and SDI-12 features work only with an Underwater Cable.

MODBUS Operation

a) How It Works

For MODBUS communication, simply connect the MODBUS Adapter Cable to the nine- pin connector on the Underwater Cable attached to your MIB-equipped Proteus. The Adapter Cable gives you the wires you need to connect the Proteus to a MODBUS device and is wired to inform the Proteus that you wish to communicate in the MODBUS format instead of the usual RS-232.
Note that the MODBUS interface can use either half-duplex differential RS-485 or full-duplex RS-232 (separate transmit and receive).

b) The MODBUS Technical Details
A MIB-equipped Proteus uses MODBUS protocol over RS-485 or RS-232 to read the parameters processed by the unit. The upstream communication functions either as a full-duplex RS-232 standard interface or as a half-duplex, RS-485 standard interface. The data format is 8-bits with no parity, one stop bit. Baud’s rate is 19,200.
The MODBUS interface provides measurement values, beginning at holding register 40001 (see Table 1), for all enabled Proteus parameters, with each measurement value occupying 2 MODBUS registers. Values are formatted in IEEE-754 32-bit floating-point representation.

Table 1: Mapping MODBUS Parameter Measurement Values

MODBUS Holding Register| Bus Address| Read Value| Format
40001| 0| Parameter 1 MSW| IEEE32
40002| 1| Parameter 1 MSW|
40003| 2| Parameter 2 MSW|
40004| 3| Parameter 1 MSW| IEEE32
..| ..| |
40035| 34| Parameter 18 MSW| IEEE32
40036| 35| Parameter 1 MSW|

In RS-485 operation, two communication lines to the MIB are used for the differential lines Data+ and Data- (see Appendix 1). In RS-232 operation, the Data+ line is connected to the Proteus Rx line, and the Data- line is connected to the Proteus Tx line. A negative voltage on the Proteus Rx signals the MIB that the Tx line from an RS-232 host is connected so that the MIB operates in MODBUS/RS-232 format; otherwise, RS-485 format is assumed. The data format is 8-bits with no parity and one-stop bit. The MIB normally operates at 19,200 baud. If you wish to change that rate, please see Table 2.

The MIB provides store/update read-only registers and reads/write settings for communicating with common SCADA systems, PLC interfaces, or other data collection platforms. A built-in MODBUS map provides aggregated sensor readings and other equipment information. The MODBUS interface provides measurement values, beginning at holding register 40001 (see Table 3), for all enabled Proteus parameters, with each measurement value occupying two MODBUS registers. Values are formatted in IEEE-754 32-bit floating-point representation. The MIB’s address is register-programmable (the default value is 1). The MIB will always respond to MODBUS address 0 if you don’t know the real address.

Table 2: MODBUS Baud Rate Indicies

Index| BaudRate
0| 9600
1| 19200 (default)
2| 38400
3| 57600
4| 115200

Table 3: MODBUS Control Register Mapping

Register| Bus Address| Read/Write Value| Format
40201| 200| Baud Rate – Upstream| Fixed at 19, 200 baud
40202| 201| MODBUS Device Address| 0
40203| 202| Baud Rate- Downstream| Integer index, 0-4
40204| 203| SDI-12 Address| Integer 0-9, A-Z, a-z
40205| 204| Power Switch Delay| Integer 0-60
40206| 205| Proteus Wipe Interval| Integer 0-1440 (minutes)
40207| 206| Proteus Wipe Freeze Time| Integer 0-60 (seconds)

c) MIB Commands for MODBUS
A MIB-equipped Proteus can be connected to a host PC or laptop to send commands directly to the Proteus CPU, as well as special commands (see Table 4) to the MIB itself. This mode of communication – using the Proteus’ normal RS-232 output and not MODBUS – is called the “transparent mode”.
When a terminal emulator, such as TeraTerm or Hyperterminal, is used to talk to the Proteus in this transparent mode, the MIB recognizes and responds to certain ASCII commands to allow the programming/verifying of some parameters, as shown below. The format of this MIB command is “$ccxxx”, where:
‘$’ indicates a MIB command
cc is a two-character MIB command identifier
xxx is a parameter value specific to the command

Table 4: Special MIB Commands

Command| Description| Parameters| Response
SAMxxx| Set MODBUS
Address| xxx ; 001 to 250| OK
$AM?| Read MODBUS
Address| none; default= 1| xxx ; 001 to 250
$WPxxxx| Write Proteus
wiper interval| xxxx ; 0000 to 1440 minutes,
default= 0| OK
$WP?| Read Proteus
wiper interval| none| xxxx ; 0000 to 1440
minutes
$WFxx| Write wipe data
freeze time| xx ; 0 to 60 seconds, default=15| OK
$WF?| Read Proteus
wipe data freeze
time| None| xx ; 0 to 60 seconds
$FV?| Read IB firmware
revision| None| IB Firmware revision

d) MODBUS Automatic Wiper Operation
Some Proteus models include a sensor-cleaning wiper built into the turbidity sensor. The wiper clears debris, foulants, and bubbles from the sensors’ active faces when the Proteus is first powered-up, and when a WIPE command is sent to the Proteus. If your Proteus is continuously powered during MODBUS operation, you may wish to periodically initiate wipe cycles using MIB commands (see Table 4). The Wipe Interval is the number of minutes between wipe cycles.
Note that setting the Wipe Interval to 0 disables automatic wiping.
Some parameter values are invalid during normal wiper cycles because of the movement of the wiper. When the cycle ends, the data resume their real-time format. But if your MODBUS controller may create an alarm on account of the invalid data during the wipe cycle, you can use MIB WIPE commands (see Table 4) to “freeze” all sensor data while the wiper is cycling. That means that all data coming from the Proteus during the wiper cycle is the same data sent in the last data transmission before the wipe cycle started, i.e. the readings stay the same during the wiper cycle.
This programmable freeze time sets the number of seconds (default is 15 seconds) that the data are frozen after the Proteus is given a WIPE command. The data resume their real-time format after that number of seconds has passed.

Using the MIB for SDI-12 Communication

a) How It Works

For SDI-12 communication, simply connect the SDI-12 Adapter Cable to the nine- pin connector on the Data Cable or Underwater Cable attached to your MIB- equipped Proteus. The Adapter Cable gives you the wires you need to connect the Proteus to an SDI-12 device and is wired to inform the Proteus that you wish to communicate in the SDI12 format instead of the usual RS-232 format (i.e. transparent mode). Appendix One shows the wire assignments by color.

b) The SDI-12 Technical Details
The host computer-to-Proteus communication adheres to requirements of the SDI-12 Support Group, Version 1.3. Table 5 summarizes the implemented SDI-12 commands. If you are not familiar with the SDI-12 Protocol, the SDI-12 Support Group website (www.sdi-12.org) provides more detail.

Table 5: MIB SDI-12 Commands (a = SDI-12 address)

a!| Empty Command|
aAl| Change address|
aC!| Request a concurrent
measurement| returns up to 20 values
aM!| Request a
measurement| returns up to 9 values
aMl!| Request an additional
measurement| returns up to 9 additional values
aM2!| Request an additional
measurement| returns up to 2 additional values
aCC!| Request a concurrent measurement with CRC|
aMCI| Request a measurement with
CRC|
aDn!| Read measurement results data| n=0..2
all| Request device identification string|

c) Special MIB Commands for SDI-12
A MIB-equipped Proteus can be connected to a host PC or laptop to send commands directly to the Proteus CPU, as well as special commands to the MIB itself. Using the Proteus’ normal RS-232 output and not SDI-12 output is called the “transparent mode”.
When a terminal emulator, such as TeraTerm or Hyperterminal, is used to talk to the Proteus in this transparent mode, the MIB recognizes and responds to certain ASCII commands (see Table 6) to allow the programming/verifying some parameters, as shown below. The format of this MIB command is “$ccxxx”, where:
‘$’ indicates a MIB command
cc is a two-character MIB command identifier
xxx is a parameter value specific to the command

Table 6: MIB Transparent-Mode Commands

Command| Description| Parameter(s)| Response
$ASx| Set SDI-12
Address| x= 0-9, A-Z, a-z; default= 0| OK
$AS?| Read SDI-12
Address| None| x ; x= 0 to 9, A-Z, and a-z
$PDxx| Set power-off
delay (extend
Proteus+ power
ON-time from
the last measure
command)| xxx= ) to 60 seconds; default= 30
seconds| OK
$PD?| Read power-off
delay| None| xxx ; x= 0 to 60 seconds
$FV?| Read IB-
firmware
revision| None| IB Fireware revision

Table 7 shows example SDI-12 commands and responses for a Proteus for which 10 parameters have been selected for SDI-12 monitoring.

Table 7: Sample 501-12 Commands and Responses for a Proteus with 10 Parameters
Selected

Command| Response
0!| O
01!| 013 PROTEUS 711SN10162469
OV!| 00000
OM!| 00169
000!| 0+0+408.6999+4938.999+489.3999
1!| 0+4494.399+132.6000+3651.699+131.2000
2!| 0+2269.900
0M1!| 00031cLF>
000!| 0+11.70000
OC!| 000310
000!| 0+0+1.800000+2.100000+489.6999
1!|
0+4523.299+133.1000+3591.099+132.2000
2!| 0+2243.600+11.72000
OMC!| 00039
000!| 0+0+1.900000+2.100000+488.999AD
1!| 0+4538.699+133.0000+3557.699+132.4000@Zy
2!| 0+2224.000NWS
OMC I!| 00031
000!| 0+11.680008S
OCC!| 000310
000!| 0+0+1.900000+2.000000+489.0999EHG
1!| 0+4546.699+133.100.3540.199+132.600001X
2!| 0+2214.500+11.70000CSh