MODBUS

Modbus is a serial communication protocol developed by Modicon published by Modicon® in 1979 for use with its programmable logic controllers (PLCs). In simple terms, it is a method used for transmitting information over serial lines between electronic devices. The device requesting the information is called the Modbus Master and the devices supplying information are Modbus Slaves. In a standard Modbus network, there is one Master and up to 247 Slaves, each with a unique Slave Address from 1 to 247. The Master can also write information to the Slaves. Read more about MODBUS here.

General

How is ModBus used with DDUtil? Just about any hardware can be controlled using ModBus here are a few examples.

• Generate TTL BCD band data to band switch amps, antenna switches, low-pass filters.
• Generate Voltage Level band data.
• Split a single key-line into multiple key-lines for transverters.
• Generate sequencing events for transverters.
• Select one of multiple antennas using band data or macros.
• Monitor (scan) digital or analog lines for predefined changes and then operate on these changes.
  • Monitor a temp sensor and turn a cooling fan on/off.
  • Monitor SWR and open the PTT line if a predetermined value is reached.
  • Monitor the PTT line and turn on an On-Air sign.
• Activate/control remote tuners

Setup

Controls

Scan Parameters

This is data contained in the MODBUS data file and represents the inputs that need to be scanned by the PLC.

• Addr → The location on the MODBUS of the PLC and modules.
• Point → The specific point address of the Input or Output bit to be scanned on.
• OnMacro → Macro to execute if the point changes from false to true.
• OffMacro → Macro to execute if the point changes from true to false.

File Controls

• File Name → A unique file name to hold the scan data. This file is located in the %APPDATA%/DDUtil_V3?ModBus/ directory.
• Load → When pressed this button will open a file input dialog box so a file may be selected and loaded.
• Save → When pressed this button will open a file save dialog box so the loaded data can be saved.

Warning! The file name needs to be unique to prevent future versions of DDUtil from over-writing the data file.

Port Controls

• Comm → The MODBUS port communication Baud Rate.

Note: all baud rates default to Eight Data Bits, No Parity and One Stop Bit (8N1).

• Port → Serial port to connect with the MODBUS PLC.

Scan Controls

• Enable Scanning → When selected will cause DDUtil to read the data points in the Scan Parameters file and execute the macros as required.

BCD Output

This is intended as another output port for the Band Data file on the LPT tab. This feature requires a Digital Output Module capable of sourcing 5 vdc at a few mills.