Funnily enough, back in 2013, I came across a geocache in Kassel that had an LED platform display mounted to a lamp post on a sidewalk. When you came close, it showed you the coordinates for the next stage. I have now learned that this was actually right next to SaF's (the manufacturer) premises - hence why there was just a random display mounted there - and the geocache owners got them to collaborate. And now, I finally have a display made by SaF myself. Too bad they're bankrupt now.
@cato This has triggered major nostalgia over here.
One of my earliest projects was an info screen in a Jeweller's window. (1984 at a guess).
I'm tempted to go and try and find the source code on 40 year old 3.5 inch floppies.
UCSD system pascal on an 8086 + z80 assembler on a custom display driver + 3 displays. The rest is a bit misty - although I think we snatched the fonts from the computer's VGA display and sent the bitmaps over serial to the z80 at boot time.
The main control board here is a delight. It's nicely labelled and shows that it supports several communication interfaces, including RS-232, RS-485 2-wire and 4-wire, IBIS and Ethernet. It also explains some DIP switch settings. There's also an EEPROMS labelled "Config" and four EEPROMs labelled "Fonts", even named F1 through F4. That's cute :3
Ah! CCL seems to be the brightness levels as measured by the front and back sensor, branding from 0 to 255. 10V seems to be the brightness level of the display, also 0 to 255!
According to the "Config" EEPROM dump, this thing is called "compact class ZZA", ZZA meaning Zugzielanzeiger (train destination display) in German. They also left a Hello world in there. :D
The fonts are variants of a font called HLB_10, which makes me wonder if they were designed to be used by the Hessische Landesbahn (HLB) train operator...
Interesting - the LED modules in this display aren't actually made by SaF themselves. They're off the shelf LUM-512H modules by Rohm Semiconductor. Never seen that before!
Giving up for now since I have no lead on how to find info about the communication protocol. I could always reverse engineer the protocol between main controller and LED row controllers, or even control the LED modules directly, but that's for another day.
Turns out that bundled with the LED display was another test setup. It seems to be a similar setup to the LCD board, but with just one 8-character LCD and an Ethernet-serial converter (?) attached to it. Curiously, the serial connection is paralleled to the LED display, even though that has an Ethernet cable going into it. I guess it was just a shared data connection for testing.
After replacing a blown fuse, it works, but clearly the firmware on that is not the correct one. It seems to be designed for a different display, that's why it shows garbled pixel data.
The alternative firmware I have sadly also doesn't work correctly. But anyway, the included serial converter seems to be sending data. Maybe this can help me figure out the protocol...
Let's look inside the LCD one first. Some loose parts that I can't see missing anywhere, as well as an entire EPROM that's just loose in there. The display sat out in the rain for some time, luckily upside down, so there's not much damage. It's smelly though...
The loose EPROM might be a spare or alternative firmware. The label says "LCC500 2cm", the same as the EPROM in the lower of a stack of two control boards. The upper one has an EPROM with a label "LCC517a" in that spot.
The display curiously has this board, which has a potentiometer on it. On the front side, there's a small hole that allows access to this potentiometer. I wonder what that's for - I could see it being the brightness adjustment for the backlight, or the contrast adjustment for the LCDs!
Back to the displays! I am taking a closer look at the LCD one now. Since there are several loose cables that don't seem to have a place, some connectors and a lose EPROM in there, I really think that this display was a kind of testing environment for the manufacturer. This would also align with the story told by the seller, who said it was from a liquidation. So it would make sense that this was on their premises.
I dumped some ROMs and found strings hinting at the Darmstadt transportation authority (HEAG) in there, as well as... the Vienna stock exchange? Really seems like they just took some firmwares they had laying around and threw them on there for testing.
The lower of the two boards (the one not connected to anything) has the "LCC500" firmware on the EPROM (with Vienna stock exchange references) and has this jumper in the IC socket. The upper control board (which was fully connected) had the "LCC517a" firmware (with HEAG references). The lose EPROM was a second LCC500. Seems like they added the upper control board later and then updated the firmware at some point...
Hypothesis time! So the left of the two big boards is going to be the main controller. It has two 10-pin ribbon cables going out at the bottom as well as two 4-pin ones. These are probably the data for two rows of LCD modules (the 10-pin ones) as well as their respective alternating blinkers (the 4-pin ones).
There's also a 10-pin ribbon cable at the top, which goes to a third board which I haven't had a closer look at yet, but it looks like the power supply and backlight brightness controller.
The main controller also has a 6-pin ribbon cable which goes to a DE-9 connector and connects to an RS-232 transceiver on the board, so that's our main communication interface. Then there's also the 20-pin ribbon cable at the top left of the main controller, which goes to the bottom expander board on the right.
This has four more pairs of 10 and 4 pin ribbon cables, as well as another 20-pin output, which goes to the top expander board (not shown here), which in turn has two more sets of 10/4 pin cables. In total, this gives us 8 pairs of 10/4 pin cables, which is exactly what we can see in the 8 rows of LCDs.
So this is the power supply unit. The orange twisted pair goes outside and is just cut off there. Not sure what that was for. It also seems like there used to be an additional board on top judging by the plastic spacers. It also has plastic spacers at the bottom, in the holes where the metal pegs in the case would normally go. I'm just going to remove those and mount it as intended.
They really put a bare steel wire in there to keep the front from opening too far. It could easily short some of the display connections or even the lamp sockets...
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