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:
The module back reveals the controller board and connectors:
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:
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:
