GB2563024A - A method and apparatus for autonomously setting addresses of a plurality of slave devices - Google Patents

A method and apparatus for autonomously setting addresses of a plurality of slave devices Download PDF

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Publication number
GB2563024A
GB2563024A GB1708577.0A GB201708577A GB2563024A GB 2563024 A GB2563024 A GB 2563024A GB 201708577 A GB201708577 A GB 201708577A GB 2563024 A GB2563024 A GB 2563024A
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Prior art keywords
modbus
slave
master
controller
slave devices
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Withdrawn
Application number
GB1708577.0A
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GB201708577D0 (en
Inventor
Sudey Bharath
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Flakt Woods Ltd
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Flakt Woods Ltd
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Publication date
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Priority to GB1708577.0A priority Critical patent/GB2563024A/en
Publication of GB201708577D0 publication Critical patent/GB201708577D0/en
Publication of GB2563024A publication Critical patent/GB2563024A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H04L41/0803—Configuration setting
    • H04L41/0806—Configuration setting for initial configuration or provisioning, e.g. plug-and-play
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L61/00—Network arrangements, protocols or services for addressing or naming
    • H04L61/50—Address allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L61/00—Network arrangements, protocols or services for addressing or naming
    • H04L61/50—Address allocation
    • H04L61/5038—Address allocation for local use, e.g. in LAN or USB networks, or in a controller area network [CAN]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
    • G06F13/38—Information transfer, e.g. on bus
    • G06F13/42—Bus transfer protocol, e.g. handshake; Synchronisation
    • G06F13/4247—Bus transfer protocol, e.g. handshake; Synchronisation on a daisy chain bus
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2213/00—Indexing scheme relating to interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
    • G06F2213/0052—Assignment of addresses or identifiers to the modules of a bus system
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L2012/40208—Bus networks characterized by the use of a particular bus standard
    • H04L2012/40228—Modbus

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)
  • Programmable Controllers (AREA)

Abstract

A method and apparatus for autonomously setting addresses of a plurality of Modbus slave devices, including a Modbus master controller 10, and means to connect the plurality of slave devices 12-18 electronically to the master controller in a daisy chain arrangement, each slave device comprising a switching means, Modbus bridge 24, to internally open or close the bridge between its two communication ports, input 20 and output 22, and having a slave reconfiguration algorithm, set Modbus ID mode, that enables the controller 10 to send messages to the slaves to control their internal Modbus bridge and set unique Modbus IDs to them autonomously in turn. The controller initially opens all of the bridges such that a reset message sent from the controller is acted upon by the first device 12 only [Fig 1.3], once the first device has sets its ID it sends a response to the controller and closes its bridge [Fig 1.4], such that the next reset message from the controller is received by the second device 14 which receives its unique ID from the controller, sends a response and closes its bridge [Fig 1.5] to allow the third slave device to be reset next and so on.

Description

A method and apparatus for autonomously setting addresses of a plurality of slave devices.
The present invention relates to a method and apparatus for autonomously setting addresses of plurality of slave devices such as, a plurality of inverters, motors and/or sensors in a bank of machinery.
It is known to use communication protocols to monitor and control such devices and one known protocol is a widely used standard known as Modbus. In such a system each device, which is typically known as a slave device, has a communications module incorporated therein so that a master device will be able to send messages to the communications module of the slave device or devices to get information or set parameters. For instance, a master device like a PC (Personal Computer) or PLC (Programmable Logic Controller) will be able to send messages to a slave device like an inverter to get information about parameters like temperature, voltage-output, outputfrequency and/or to send control messages instructing it to set its parameters; like voltage-output or output-frequency.
Typically, all the devices will be connected to the same communication infrastructure and hence every message from the master will be received by every slave device on the communication infrastructure. For the master to distinguish between the devices, it is necessary that each slave device has a unique identifier code called Modbus ID. Every message from the master will include the Modbus ID of the intended recipient device so that the unintended recipients of the message can ignore the message while the intended recipient perform the requested function and respond back to the master with a reply message. The slave devices are not allowed to initiate a communication and can only respond to the messages it receives from the master.
Out of the box, every Modbus slave device typically will have a Modbus ID of 1. It is an established practice that each slave device has to be individually powered up and then given a unique Modbus ID, typically using a configuration message from the master device. It is only after allocating each device its own unique Modbus ID that the devices can be connected up into a single common communication infrastructure controllable by the master device. This process is difficult and time-consuming depending on the number of devices as it must be done manually on an individual basis.
In another known system, each device can be given a unique Modbus ID even when connected to a common communication infrastructure if the individual device’s serial number is known. In this system, the master can set Modbus IDs of devices by sending configuration messages with the serial number of the intended device so that only the intended device will process the message while the unintended recipients ignore it. However, this is a manual procedure and relies on the prior knowledge of the serial numbers of devices on the communication infrastructure. Furthermore, different types of devices and/or devices from different manufacturers can have same serial numbers thereby making such a reconfiguration impossible. Although in this system it is not necessary for the devices to be powered up individually, it requires manual intervention of looking up the serial number and of allocating appropriate unique Modbus IDs thereby posing an inevitable risk of human error.
The present invention seeks to provide a solution to the disadvantages of the known systems by enabling unique IDs to be allocated to each device in a plurality of devices by the master device autonomously.
According to the present invention there is provided apparatus for autonomously setting addresses of plurality of slave devices, including:
a master controller, means to connect the plurality of slave devices electronically to the master device in a daisy chain using a communication infrastructure, slave devices with two communication ports and means to electronically disconnect the connection link between the communication ports, each slave device having a unique ID which is used by the master device to designate the intended recipient device on its messages, the master device being adapted to autonomously generate unique IDs for each device in the daisy chain and to configure the device with the unique ID to enable the master device subsequently to communicate specifically with the slave device given that ID.
Preferably, the master controller is able to control the setting of the connection link on slave device, which enables the master to send unique IDs to individual slave devices.
In preferred arrangements, the apparatus enables slave devices to respond to messages from the master to open or close its connection link and allow ID allocation.
The invention also provides a method of controlling the apparatus by utilising a method of communication comprising a standard protocol, which preferably is the Modbus protocol.
An embodiment of the present invention will now be described by way of reference to accompanying drawings, in which:Figure 1.1 shows in schematic form a master device and four slave devices connected in a daisy chain to the master controller,
Figure 1.2a shows schematically the default setup of the proposed internal Modbus bridge between the two communication ports in a slave device,
Figure 1.2b shows schematically the open setup (for device configuration) of the proposed internal Modbus bridge between the communication ports in a slave device, Figure 1.3 shows a daisy chain of four slave devices in which the internal Modbus bridges between the communication ports are open (for device configuration),
Figure 1.4 shows an arrangement in which the second and subsequent devices have open Modbus bridges between their communication ports and the first device has a closed Modbus bridge between its communication ports,
Figure 2 shows a flowchart of an algorithm that enables the master to autonomously reconfigure Modbus IDs of devices in the daisy chain.
Figure 3 shows a flowchart of an algorithm that enables slave devices to get autonomously reconfigured by a master device.
Referring now to Figure 1.1, there is shown in schematic form a layout in which a master controller 10 is connected to four slave devices 12-18 in a daisy chain arrangement. The slave devices 12-18 comprise a controllable device such as an electric motor but it is not necessary for the devices to be identical. The devices may, for example, be airconditioning equipment, cooling equipment, pneumatic pumps, sensors for example, typically mounted in a large industrial complex of machinery.
Each slave device incorporates two connection ports for communication, one input 20 and one output 22. As shown on the slave device 12 the two ports 20, 22 are connected in the slave device through a switch device 24 called Modbus bridge. The switch device 24 are closed by default and can be mechanical or solid state. Each slave device incorporates its own control circuitry (not shown). As shown, the output 22 of the slave device 12 is connected to the input 20 of the slave device 14, the output 22 of which is connected to the input 20 of the third slave device 16 and so on down the daisy chain.
As shown, all the Modbus bridges 24 of the slave devices are shown in the closed position so a message from the master device 10 is transmitted to every slave device in the daisy chain. The default position of each of the Modbus bridges 24 is the closed position as shown in Figure 1.1 to enable messages from the master controller 10 to be transmitted to all slave devices in the chain.
As shown in Figure 1.2a, the slave device 12 is shown with its Modbus bridge 24 closed to provide a connection between the input 20 and the output 22. As shown in Figure 1.2b, the slave device 12 is shown with the Modbus bridge in the open position. In this position the slave device 12 is able to receive a message or control signal from the master controller but this signal is not transmitted to any slave devices further down the daisy chain. In this configuration the functionality of the first device 12 is preset by the automated configuration of setting its unique Modbus ID by the master controller 10.
The process of configuring the devices in the daisy chain is that the master controller 10 sends a Reset command and this message will travel through the entire daisy chain to every slave device in the chain. On receipt of this Reset command, each slave device will go into a rest mode and disconnect its internal Modbus bridge 24, as shown in Figure 1.3.
In the second step, the master controller 10 will send a “set Modbus ID” command with a unique Modbus ID. In this case the message will be received only by the first device at the input 20. On receiving the “set Modbus ID” command, the device will set its Modbus ID as per the received command and will then set itself into its normal mode closing the Modbus Bridge 24. This arrangement is shown schematically in Figure 1.4. The slave also sends a response message back to the master as a confirmation of the procedure.
Subsequent to this, the master controller 10 will send another “set Modbus ID” message to the daisy chain but the first slave device 12 will ignore this command (as it is not in reset mode) and since its switch 24 is closed will be forwarded to the next device 14 in the daisy chain. Since the second device 14 is in the reset mode, it will set its Modbus ID based on the value in the command from the master device 10. Like the first device in the daisy chain the second device 14 will then switch into its normal mode thereby engaging its internal Modbus bridge as shown in Figure 1.5 and send a confirmation message to the master. Likewise, by repeating the process, every device in the daisy chain will be allocated a unique identifier. Once every message on the chain is configured, the master would stop getting configuration response messages back as response to its “set Modbus
ID” commands as all the devices will be in normal mode. So, the lack of confirmation message will thereby confirm that all the devices are configured with unique Modbus IDs. Though the example treats one communication port on each slave as input and the other as output, they are interchangeable as the logic will work regardless of the connection direction.

Claims (6)

1. Apparatus for autonomously setting addresses of plurality of slave devices, including:
a master controller, means to connect the plurality of slave devices electronically to the master device in a daisy chain using a communication infrastructure, slave devices with two communication ports and means to electronically disconnected the connection link between the communication ports, each slave device having a unique ID which is used by the master device to designate the intended recipient device on its messages, the master device being adapted to autonomously generate unique IDs for each device in the daisy chain and to configure the device with the unique ID to enable the master device subsequently to communicate specifically with the slave device given that ID.
2. Apparatus according to claim 1, wherein the master device is able to control the setting of the connection link on slave devices.
3. Apparatus according to claim at 1 or 2, that enables the master to send unique IDs to individual slave devices.
4. Apparatus according to claim at 1, 2 or 3, that enables slave devices to respond to messages from the master to open or close its connection link and allow ID allocation.
5. A method of controlling the apparatus according to claims 1, 2, 3 or 4, by utilising a method of communication comprising a standard protocol.
6. A method of controlling apparatus according to claim 5, wherein the standard protocol is the Modbus protocol.
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GB1708577.0A 2017-05-30 2017-05-30 A method and apparatus for autonomously setting addresses of a plurality of slave devices Withdrawn GB2563024A (en)

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Publication number Priority date Publication date Assignee Title
US10805262B1 (en) * 2019-06-10 2020-10-13 Banner Engineering Corp. Modbus system having actual and virtual slave addresses and slave sensors

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5768277A (en) * 1994-07-25 1998-06-16 Matsushita Electric Works, Ltd. Automatic ID assigning device for network instruments
EP1320222A1 (en) * 2001-12-13 2003-06-18 AMI Semiconductor Belgium BVBA Multiplex transmission system with in-circuit addressing
EP1553726A1 (en) * 2002-10-25 2005-07-13 Citizen Watch Co. Ltd. Electronic device system
US20120221755A1 (en) * 2009-07-27 2012-08-30 Karl-Heinz Schultz Device and method for addressing a slave unit
EP2571200A2 (en) * 2011-09-16 2013-03-20 Nxp B.V. Network communications circuit, system and method
US20160364354A1 (en) * 2015-06-10 2016-12-15 Solomon Systech (Shenzhen) Limited System and method for communicating with serially connected devices

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5768277A (en) * 1994-07-25 1998-06-16 Matsushita Electric Works, Ltd. Automatic ID assigning device for network instruments
EP1320222A1 (en) * 2001-12-13 2003-06-18 AMI Semiconductor Belgium BVBA Multiplex transmission system with in-circuit addressing
EP1553726A1 (en) * 2002-10-25 2005-07-13 Citizen Watch Co. Ltd. Electronic device system
US20120221755A1 (en) * 2009-07-27 2012-08-30 Karl-Heinz Schultz Device and method for addressing a slave unit
EP2571200A2 (en) * 2011-09-16 2013-03-20 Nxp B.V. Network communications circuit, system and method
US20160364354A1 (en) * 2015-06-10 2016-12-15 Solomon Systech (Shenzhen) Limited System and method for communicating with serially connected devices

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