The VP-EC-RDU Remote Display 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.
The VP-EC-RDU
The design is based on the PIC18F45K20 processor, has the ICSP port available for programming and product development, a RS485 port, etc.
Here are the schematics:
Here is the VP-EC-RDU in the enclosure with Graphic Overlay:
Specifications:
- Low Power (9 - 24 VDC typical, max 28 VDC)
- LCD Display 4 Line x 20 Character, White Characters, Blue Background (Other colours 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.
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
Here are other views of the display:
