Unknown LCD 54 pins used in a "pricer"

Hello u all :)

Here is a challenge !! last week, I found this "pricer" on the parking lot of an hypermarket. It didn't display anything, but anyway, I brought it home :grin: ! I changed the batteries, and OK, it works. Now, I'd like to try to make it work with my arduino Uno. The problem is that I don't know how to interface with it. as you can see, the "controller" is hidden ! I suspect it to be an atmega 169, but ..... As far as I know, the display can be changed with IR command. maybe I will be able to send a signal directly on the right pin (bypassing the IR receiver) ? Here is an overview of the item. I've also made some copies of the signals on each pin, depending of what is displayed. There is a "8888" display when I power it on, which last only about 30 seconds, the a "AAAA" display wich is there as long as it is ON. I'll put them here ASAP (it's not really easy with imageshack, because of the names, and I couldn't join the files directly from my drive, I don't know why) , but if anyone has already an idea about it....

thanks a lot for your help, I really would like to make it work :)

Here is the signal on pin "1" (the one near the quartz) when "8888" is displayed :

and here, the same pin, when "AAAA" is displayed :

The quartz sends a 32kHz signal (sine wave actually) and the frequency on the pins are 32Hz (in some cases 96Hz)

Here the signal on the next pins, when "AAAA" is displayed (i call "AAAA" the display shown on the 3rd image in my first post )

pin 2 :

pin 3 :

pin 4 :

next images to come (don't panic, there are not much left ;) )

pins 5 to 21 :

pin 22 :

pin 23 :

pin 24 :

OK, we're almost done (sorry for the number of pictures, but...)

pin 25 :

pin 26-54 :

and here is a closer view of the PCB:

I think that the device where there is "D1" is the IR receiver, no ? It shows a 1Hz signal on the "+"

OK, you have all that I have Excuse me again for the posts and pictures, but I think it is better to give all the details than to wait for questions.

Thank you for any help :)


Oh, one last thing : for now, I don't want to use all the LCD possibilities, just the 4 "big" digits will do for a try :) Then if any of you know the pinouts of this LCD , or could give me an advice about how to find out, it's OK . I'm doubtful about using the controller hidden, but if I know the pinout of the LCD I'll be able to connect it with another one ;)

Thanks again :)

PS : maybe I should have posted this topic in the "display" section ? Modos/admins, please feel free to move it if you think it is not the right section

A 32.768KHz crystal and a 1Hz output on a pin? Sounds like you are looking at an Real Time Clock circuit. I wouldn't rule out using the built in control chip just yet. It is hard to see on your pictures, but how was this board originally connected in the circuit?

no, the crystal is a 32.768KHz, but, on the LCD pins, the signal is mostly at 32,1Hz , except on pin "23" (or "31" depending on the real number "1" ) on which it is at 96,2 Hz It seems to be OK as far as I know, for a LCD display.

The 1Hz signal is the one on the "+" pin of the component (maybe the IR receiver ? ) which on the right on the photo, just under the letters "D1" . I guess that the signal changes there only when they send an IR signal in order to change the informations displayed (new price ...) .

The connexions are as they were. I've just replaced the original batteries bay a new one, and put a red wire on the "+" and a blue one at the "-"

I agree, and I don't really hope to use the control chip. I'd be happy if I could get a "datasheet" of the LCD alone, or at least a pinout of it.

So this originally worked only wireless? Something sent information over IR and it displayed. You can likely eventually reverse engineer it but in the end you will need either an FPGA/CPLD or a full LCD segment driver to control the bare LCD. I don’t think it would be worth it to me. You can buy fully documented LCDs pretty cheap.

Personally (and this is just me) I would do all I could to attempt to hack the control circuit and if I couldn’t get anywhere with that, it would end up in my junk bin.

However, if you persist, your next step would be to find the “common” pin and the other 53 pins will be the segment pins. The common is likely your 96Hz pin as it would want to cycle through the segments quickly so you didn’t see flicker. During each cycle, the 53 different segments will be set to on or off. So once you find the common, you can sort out the segments by driving each pin individually and noting what segment lights up (or turns off since your board is already driving it.) And again, in the end, you will need to build some circuit that can drive the 53 segments or use a segment driver. These are what you would be working with:


The question still remains… why would you see a 1HZ pulse OUTPUT going to an IR RECEIVER? Typically an IR receiver would be connected an interrupt input on a controller. My guess is that you are either just seeing noise or it is something different than you think.

thanks for your answer and advice :slight_smile:

yes, it works only wireless, I think it comes from here : http://www.pricer.com/fr/Solutions/Etiquettes/

I want to try, yes, just for fun and because I like it, and I’ll do what you suggested to find the common and other pins.
And if I find the pinout, yes I’ll buy a cheap LCD controller.
Hacking the control circuit was my 1st idea, but I still don’t know which controller it is, and it is impossible to remove the black “cap” on it !!
Maybe I’ll try 2 or 3 things anyway :wink: -

The problem is that most controllers are for 14 or 16 pins LCDs … this one has 54 ! that’s why I need to find the pinout and I’ll drive only the segments I need (driving the others so they stay OFF)

Yes again, the question remains about the 1Hz signal. I’m pretty sure it is no noise, because it is a square 3V signal, 1Hz steady. But I’m not
sure that it is the IR receiver :wink:

Thanks again, I’ll have a look at the link you posted :slight_smile:

alnath: The problem is that most controllers are for 14 or 16 pins LCDs .... this one has 54 ! that's why I need to find the pinout and I'll drive only the segments I need (driving the others so they stay OFF)

Well, not when you start looking at raw segment decoders. Typically they are arranged in commons and segments. The ATMegq169 used in the AVR butterfly for example controls 4 commons and up to 25 segments. Your LCD probably also has multiple commons, I'm sure. In fact, the ATMEGA169 might even possibly work for you and there was some work done to get Arduino working on it.

Take a look at the datasheet. It has a pretty good explanation of how a raw LCD controller works and might give you some information to help you reverse engineer this: http://www.atmel.com/images/doc2514.pdf

yes, I think it has multiple commons too. I saw the atmega169 datasheet, two days ago, and downloaded it, but I just looked quickly . I'll read it thoroughly . You are right, it might work, and even if it didn't, I'll learn a lot :)