VP-EC-RDU LCD Display Modbus RTU RS485 DIN  Enclosure

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

Regular price $94.50 USD Sale

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.

An added bonus is the board temperature sensor (10K 3380 Beta Thermisor) that can be displayed and read via it's Holding Register.


  • Low Power (9 - 24 VDC typical, max 28 VDC)
  • Power Consumption: 20mA @ 24VDC, 11mA @ 12VDC
  • 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)
  • Modbus ID Programmable
  • Modbus RTU Protocol
  • Compact, Rugged Case
  • 4x20 LCD Backlight Programmable  Always ON, Timed Off
  • Simple Operation Read and Write Modbus Holding Registers
  • Wall Mount Enclosure Dimensions 4" x 6" x 1.25"
  • DIN Enclosure Dimensions 3.7" x 5.45" x 1.1"
  • Microchip PIC18F Series Processor c/w ICSP connection
  • Arduino and Raspberry Pi compatible when using RS485 with Arduino and Raspberry Pi projects
  • Temperature Sensor (10K 3380 Beta Thermistor), temperature calculated using a Steinhart-Hart equation.

Three versions of this product are available:

Model: VP-EC-RDU-DIN is the complete unit with a DIN Rail mount case, assembled and tested

Model: VP-EC-RDU is the complete unit with a wall mount case, assembled and tested

Model: VP-EC-RDU-PCB is the same except without the case and graphic label.

PCB Dimensions: 5.175" x 3.435"

For OEM's, we will provide a custom graphic label on quantities of 100 or greater. Please contact us for further details.


Field Connections:



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 2
41             Status LED 1
42             Audible                   0 = OFF, 1 = ON

Status LED States are defined as follows:

OFF                                     0x00
GREEN                                0x01
GREEN FAST FLASH         0x21

AMBER                                0x02

AMBER FAST FLASH         0x22

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

Download the User Manual

VP-EC-RDU User Manual

Python Sample Code for the Raspberry Pi 3:

pispi_rdu_lib.py  VP-EC-RDU Python Library

pispi_rdu_test.py  VP-EC-RDU Test Code


For Modbus Registers and programming information, please visit the product page at vpprocess.com.

For a more economical approach, look at the new VP-EC-RDU-MINI display