unknown display recycling

[amperium]

Hi,
I recently purchased two of these taximeter displays. As the display is quite handy and nice
I'd like to use in for a 'smart clock' project. Unfortunately, I can't find any data for this
display module online. Does anyone know which module that might be, or could guess a
pinout / protocol?
Thanks! 

[james_s]

Is it a dot matrix alphanumeric type? If so then I think there's a reasonable chance that it's compatible with the HD44780, that's a bit of an industry standard. I would start by working out where the power and ground pins are, ground is normally easy since the shield will connect to it, power can be a little trickier but often there will be a capacitor between it and ground. Look up the 44780 display pinout and see if it seems to match.

[amperium]

Thanks for your answer. According to a picture of the device on the companies website, it's a graphical dot matrix one.
Alright, I'll have a look.

[james_s]

Oh that's a graphical display so it won't be a 44780. It may be one of the other fairly standard graphical LCD controllers though. Do you have the equipment they came from? It may be possible to look at the signals it puts out.

[amperium]

Unluckily, I only got the entire display module consisting of the display module itself, the frame and a second PCB attached to it with lots of 20-pin connectors on it.
I don't know if it works as a stand alone device. 

edit: the 7th pin of the 28-pin connector to the display PCB could be GND, 4th pin = Anode of backlight (= vcc?)

[helius]

The 4-pin ribbon might well be I²C or RS232, and the 28-pin ribbon is some kind of parallel connection. Most of them are 4-bit or 8-bit parallel with clocks and R/W and so on. Reverse engineering it can be hard without docs or a working controller

[amperium]

Contrary to what I expected, the company replied to my email asking for the type of the display.
One of the product engineers sent me the data sheet.  It's an EPSON S1D15712 type display module.
Nevertheless, thanks a lot for your help.

[amperium]

Hello,
Today I had a read through the entire data sheet but I still can't figure
out the pinout. Neither of the parallel port nor of the simple I2C connector.
I tried to probe resistance against a ground plane and against the other pins to find pull-up resistors. Unfortunately,
without success, the resistance between those 4 pins is always infinity (O.L.).

I've attached the data sheet. I'd be very happy if anyone could help me. Thanks.

[james_s]

That's the datasheet for the controller chip integrated into the display, so it won't have the pinout of the display itself. You might search for other displays that use the same controller chip and see if you can find a datasheet for one of those displays that shows the pinout.

[bktemp]

Based on the number of pins on the cable, it uses most likely 8bit parallel bus.
The 4 pin connector could be for an optional touchscreen, I doubt it has any connection to the LCD itself.

Since you know the controller, you have the pinout of the LCD itself: Look at page 7 in the datasheet. Often not all pins are used, but they are in the same sequence as the pinout of the chip.
I would start at probing each of the ~50 pins on the LCD. Many of them are probably connectly to the input cable, some are connected to Vcc or GND and some are connected to capacitors on the pcb (C1-C6).
If you measure all signals and give me that table, I can probably figure out the pinout of the 28 pin cable.

[capt bullshot]

Which company did you ask for the datasheet?
The number "EA..." points towards http://www.lcd-module.de/ but I guess this is a non-public OEM display for Kienzle that made the taxameter.
Inside the datasheet is the pinout of the naked controlled chip, by counting and guessing you might be able to figure out the pinout of the large flat cable (ususally there are no or very few crossover lines from the flip chip to the solder ends of the black film).