MODBUS

Based on MODBUS Application Protocol Specification V1.1b3

This capability is provided by LiveRig Collector 2.28.0 or higher

The MODBUS protocol is capable of receiving data from a PLC (programmable logic controllers) device via TCP connections if LiveRig is older than 5.0.0, otherwise the data can be received via TCP, UDP and Serial connections.

There are a number of memory areas defined in the MODBUS specification. Here, are the types of data supported, by the LiveRig Collector:

• Coils

  • Discrete Input - Boolean input value, usually representing a binary input to the PLC

  • Coil - Boolean value, usually representing a binary output from the PLC

• Registers

  • Input Register - Short input value, usually representing an analog input to the PLC

  • Holding Register - Short value, usually representing an analog output from the PLC

Configuring the endpoint field for Modbus sources

LiveRig Collector 5.0.0 or above

If you are using a LiveRig version 5.0.0 or above, you can change the connection protocol by declaring the endpoint using the format: {code}:{transport}://{ip-address}:{port}?{options}. Here is a list of options:

• code: modbus-tcp(default), modbus-adu, modbus-ascii;

• transport: tcp(default), udp, serial;

• options: request-timeout, unit-identifier (This will use the following structure: ?{option-1-name}={option-1-value}&{option-2-name}={option-2-value})

The transport, port and options fields are optional. The default port value is 502 and if the code value is just modbus, it will default to the modbus-tcp value.

Example TCP Modbus endpoint:

modbus-tcp:tcp//127.0.0.1:1552

Example Serial Modbus endpoint:

• For Linux Systems: modbus-adu:serial:/dev/ttyUSB0

• For Windows Systems: modbus-adu:serial:COM1

Note: You need to add a special permission to access serial Sources on Linux. This can be done by adding the user to the dialout group using a sudo usermod -a -G dialout $USER command.

LiveRig Collector previous than 5.0.0

If you are using a LiveRig 4.x or bellow, you cannot change the connection protocol, so the endpoint format must be modbus://{ip-address}:{port}

Example

The configuration below opens a new connection on port 1552 (default is 502)

    <source>
        <name>Modbus TCP</name>
        <enabled>true</enabled>
        <mode>client</mode>
        <rig_name>NS03</rig_name>
        <service_company>intelie</service_company>
        <protocol_name>modbus</protocol_name>
        <protocol_version>1.1b3</protocol_version>
        <endpoint>modbus://127.0.0.1:1552</endpoint>
        <requests>
            <request>
                <revisionWaitingTime>3000</revisionWaitingTime>
                <object>pump-pressure-1</object>
                <query_period>25</query_period>
                <uid_log>1</uid_log>
            </request>
            <request>
                <revisionWaitingTime>3000</revisionWaitingTime>
                <object>water-flow-1</object>
                <query_period>10</query_period>
                <uid_log>2</uid_log>
            </request>
        </requests>
    </source>

In this example we have two PLC devices, identified by <request> node and the following information must be provided:

Name	Description	Is required?	Default value
revisionWaitingTime	Timeout, in milliseconds, after which a request is terminated.	No	Infinity
object	Name that will be fetched in modbus.json to get more information about the memory area	Yes
query_period	Interval, in seconds, for the execution of each request	Yes
uid_log	A number, between 1 and 255, that identifies the target PLC	No	1

A modbus.json is also needed to be configured in the collector, so the data can be properly retrieved.