This page documents the large LED sign acquired by Hackeriet, gifted by pere and asle.

This is an Ericsson-branded, Alpha-American / Adaptive Micro Systems 4200C LED sign.

It is a programmable LED display commonly used for transit, public information, or industrial messaging systems.

• Model: 4200C
• Manufacture Date: 2004-04-08
• Power: 100–240V AC, 50/60Hz, 1.5A
• Status: Fully operational, displaying test message on boot. Unknown operational method.
• For indoor use only.

The Microcontroller is TS80C32x2 which is compatible with Intel 8051.

Datasheet: https://ww1.microchip.com/downloads/en/devicedoc/doc4184.pdf

The device seemingly runs a custom firmware, the label on the epromm is “4200c CUST 1018-6008e”, and it displays CUST during boot.

The firmware is here:

• https://hackeriet.no/tmp/bango/dump01.BIN
• https://hackeriet.no/tmp/bango/dump02.BIN
• https://hackeriet.no/tmp/bango/dump03.BIN
• https://hackeriet.no/tmp/bango/dump04.BIN

The firmware is 128k (131072 bytes). SHA-1: e5e3bdad5e507f658a874d40483de60161152777 The Intel 8051 is designed as a Harvard architecture with two independend 16bit address buses. So the 128k dump is used as two separate ROMs of 64k each (PROM and XRAM).

The sign has a RJ-style modular port on the back panel with:

• RS-232 IN
• RS-485 IN
• RS-485 OUT

It also has an IR sensor hidden behind a red sticker, visible when removing a panel.

A small dongle with resistors was included, likely serving as a RS-485 termination and bias dongle.

The sign probably uses the Alpha Sign Communications Protocol, which is:

• A structured serial protocol using STX/ETX framed packets.
• Allows sending:
  • Text messages
  • Control commands (clear, brightness, modes)
  • Time-based messages
• Multiple signs can be connected via a RS-485 network

Suggestion for initial connection (untested):

• Interface: RS-232 IN (single device)
• Baud rate: 9600 or 19200
• Data bits: 8
• Parity: None
• Stop bits: 1
• Flow control: None

RJ-12 Pinouts, from left, clip down

1. ground → GND TTL / db9 pin 5
2. RS485 (+)
3. RXD → TXD TTL / db9 pin 3
4. TXD → RXD TTL / db9 pin 2
5. RS485 (-)
6. +5V (200ma max)

The driver board consists of: - 2x data lines (R channel + G channel) - 2x clock lines (R channel + G channel) - + 2 more lines

This analysis was performed on a dump with duplicate channels and some missing channels, so some blanks have been filled in by reasoning.

The total pixel surface of this board is 16 rows by 200 columns. We have 8 bits per module, with 25 modules per row. Total of 200 bits per row, per channel.

The entirety of one line is blasted out starting from the bottom row of the display, batched in groups of 8 bits (one-and-one matrix module, left to right). Once the red channel has been output, the same is done for the green channel on separate lines. Afterwards, the row selection is shifted one row up and the next line is output.

The line selection automatically wraps around, however it's suspected that the previous output latches are being reset using a pulse at the end of the _first line_ of a given frame.

It seems that normal configuration of the sign is done over IR with a remote control or with an IR message loader attached via the RJ-12 connector.

The a quick look at the usual resources do not appear to have a capture of the remote.

• LIRC remote configurations
• flipper IRDB

• Alpha American Technical Manuals
• Alpha® Sign Communications Protocol
• alpha - cables adapters interfaces
• C programs to control Adaptive Micro Systems LED signs which may work or may not work with our sign