Model VP-EC-RDU Modbus RTU LCD Display 4 Line x 20 Character, RS485, LED Indicators and Audible

  • $95.00

The VP-EC-RDU Remote Display by VP Process Inc. is the perfect addition to any controls system or project that uses the MODBUS RTU protocol and RS485.

The easy to read 4 line x 20 character display is simply written to by writing the applicable holding registers, along with the status LEDs and Audible. The four user buttons are read and can be programmed for different functions as required by the user's application. Arduino and Raspberry Pi projects can also use the VP-EC-RDU when using the Arduino and Raspberry Pi serial ports as RS485.

For complete details on all of our Modbus Interfaces, please visit our website at


  • Low Power (9 - 24 VDC typical, max 28 VDC)
  • LCD Display 4 Line x 20 Character, White Characters, Blue Background (Other colors available upon request)
  • 2 Programmable Status LEDs  ( Green - Amber - Red )
  • Blue Power On Led
  • Audible (Programmable)
  • 4 User Pushbuttons  (Menu, Up, Down, Enter)
  • RS485 Interface 1 External RJ45 (Cat5e), 1 Internal RJ45 (Cat5e) , 1 Internal 4 Pt. Terminal Block
  • Programmable Baud Rates ( 9600 or 19.2K Baud N81 )
  • Easy Front Cover Removal (4 Screws), Rear Panel access cutout
  • Modbus ID Dipswitch Selectable
  • Modbus RTU Protocol
  • Compact, Rugged Case
  • 4x20 LCD Backlight Programmable  Always ON, Timed Off
  • Simple Operation Read and Write Modbus Holding Registers
  • Enclosure Dimensions 4" x 6" x 1.25"
  • Microchip PIC18F45K20 Processor c/w ICSP connection
  • Arduino and Raspberry Pi compatible when using RS485 with Arduino and Raspberry Pi projects

Two versions of this product are available:

Model: VP-EC-RDU is the complete unit with case, assembled and tested
Model: VP-EC-RDU-PCB is the same except without the case and graphic label.

For OEM's, we will provide a custom graphic label on quantities of 25 or greater. Please contact us for further details.


MODBUS Functions

Modbus Function 02  Read Discrete Digital Inputs - User Pushbuttons

Address:  0

Data:   Menu =   0x01

            UP =   0x02
            DOWN =   0x04
            ENTER =   0x08             


Modbus Function 16  Write Multiple Holding Registers

The LCD uses both high and low bytes of the Holding registers and displays the ASCII characters as follows:

Holding Register Address  - Description

0 to 9       LCD Line 1  (20 Character ASCII String)
10 to 19    LCD Line 2  (20 Character ASCII String)
20 to 29    LCD Line 3  (20 Character ASCII String)
30 to 39    LCD Line 4  (20 Character ASCII String)
40             Status LED 1
41             Status LED 2
42             Audible                   0 = OFF, 1 = ON

Status LED States are defined as follows:

OFF                                     0x00
GREEN                                0x01
GREEN SLOW FLASH          0x11
GREEN FAST FLASH            0x21

AMBER                                0x02

AMBER SLOW FLASH          0x12
AMBER FAST FLASH            0x22

RED                                     0x04
RED SLOW FLASH               0x14
RED FAST FLASH                 0x24