Advantech LCD module

Table of Contents

1 Intro

The Advantech LCD manipulator is a simple module which contains a text LCD, a keypad all connected to a controller board. Advantech is a industrial and embedded computer manufacturer. Unfortunately there are no labels or P/N information on the module or the board so it's not possible to exactly identify this part. The controller has a PIC processor and an RS-232 interface chip which drives an interface connecting to a PC mainboard. This module was installed in some kind of networking appliance which I disasembled some time ago and I decided to reverse engineer the communication protocol in order to be able to use the module in my own projects. The module front looks like this:

thumb-module.jpg

The module back reveals the controller board and connectors:

thumb-module-back.jpg

2 Hardware

2.0.1 Chips

Label Type Notes
U1 PIC16F873 Placed in a precision socket
U2 ADM213  

Both chips and their surroundings have been documented on the photos below:

thumb-U1-closeup.jpg thumb-U2-closeup.jpg

2.1 Interfaces

The RS-232 interface runs at 2400 bps with 8n1 configuration. This interface uses RS-232 voltage levels therefore can't be connected directly to a microcontroller. When the module boots it sends out an "ADVANTECH CORP" string:

--- Miniterm on /dev/ttyUSB0  2400,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
 ADVANTECH CORP

Each keypress generates a 2 byte packet transmitted from the module. The keys map to the packets in the following way:

Keypress Packet
UP 0xFD 0x41
DOWN 0xFD 0x42
LEFT 0xFD 0x44
RIGHT 0xFD 0x48
ENTER 0xFD 0x50

The display protocol is also very simple. In order to display text on the LCD you need to send a string of 80 bytes to the serial port. The way the string needs to be built is show in the following code:

#!/usr/bin/env python3

import serial, sys

serial_port = sys.argv[1]
line1 = sys.argv[2]
line2 = sys.argv[3]

ser = serial.Serial(port=serial_port, baudrate=2400)

ser.write(bytes("{}{:<16}{}{:<16}".format("\x00" * 24, line1, "\x00" * 24, line2), 'ascii'))

For example, by running the command:

➜  advantech-lcd-module git:(master) ✗ python3 lcd_update.py /dev/ttyUSB0 'this is a test' '12345678'

We get the following result:

thumb-test-lines-displayed.jpg

Created: 2020-06-24 17:57

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