Modbus

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Modbus is a serial communication protocol developed for use with its programmable logic controllers (PLCs).

Website: www.modbus.org

About

Modbus is a serial communications protocol originally published by Modicon (now Schneider Electric) for use with its programmable logic controllers (PLCs). Simple and robust, it has since become a de facto standard communication protocol, and it is now a commonly available means of connecting industrial electronic devices. The main reasons for the use of Modbus in the industrial environment are:

  • developed with industrial applications in mind
  • openly published and royalty-free
  • easy to deploy and maintain
  • moves raw bits or words without placing many restrictions on vendors

The development and update of Modbus protocols has been managed by the Modbus Organization since April 2004, when Schneider Electric transferred rights to that organization, signaling a clear commitment to openness.

Before creating the bOS configuration, configure the Modbus device according to the manufacturer's instructions or contact your installer to get a configuration report (list of modbus addresses).


Help

bOS Modbus device is usually used for industrial solutions such as energy consumption metering and more advanced HVAC systems.

Modbus

Picture 1: Modbus node

Modbus driver acts as a Modbus master device. Driver offers two types of connections (TCP or RTU) defined by the Connection Type setting. TCP connection has IP and Port settings. RTU connection has serial port settings (Serial Port, Baud Rate, Data Bits, Parity, Stop Bits and Handshake). RS-232 or RS-485 serial communication can be used with a suitable USB converter. Additional timeout delay can be set.

Modbus slave devices store data in four Modbus tables:

  • Discrete Output Coils: Read, Write
  • Discrete Input Contacts: Read only
  • Analog Input Registers: Read only
  • Analog Output Holding Registers: Read, Write

Each table has 9999 values. Each coil or contact is 1 bit and assigned a data address between 0000 and 9998. Each register is 1 word = 16 bits = 2 bytes and also has data address between 0000 and 9998.

Modbus data is converted by the following data point nodes: DPT Boolean, DPT Double, DPT Integer, DPT UInt. The apropriate data Address should be entered for each data point. Slave addressing can be used for each data point. Use Slave Addressing and Slave Address settings are available. The data point nodes offers Value value to use on user interface and in tasks.

Folder node can be used to group different zones and partitions.

DPT Boolean

Node converts the data from Coils and Inputs table, defined by the Table setting.

DPT Double

Node converts the data from Input Registers and Holding Registers table, defined by the Table setting. The data can be converted from IEEE 32 Bit Float, Signed 16 Bit Integer, Unsigned 16 Bit Integer or Signed 32 Bit Integer. In case of IEEE 32 Bit Float and Signed 32 Bit Integer, 2 holding registers (4 bytes) will be read.

DPT Integer

Node converts the data from Input Registers and Holding Registers table, defined by the Table setting. The appropriate data Address should be entered. The data can be converted from Signed 16 Bit Integer, Unsigned 16 Bit Integer or Signed 32 Bit Integer. In case of Signed 32 Bit Integer, 2 holding registers (4 bytes) will be read.

DPT UInt

Node converts the data from Input Registers and Holding Registers table, defined by the Table setting. The appropriate data Address should be entered. The data can be converted from Unsigned 32 Bit Integer. 2 holding registers (4 bytes) will be read.