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How to program an LCD

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cool.man

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Hi guys
I have an LCD, see the attached files. I want to interface it with microcontroller, but i don't have its datasheet nor it has any model no or company name. Currently it is connected with some circuit, which is driving it. What i come to know is that it's 3 pins are connected to microcontroller as mentioned in the schematic
1- CS
2- DATA
3- WR

IMG_20171019_160156.jpgIMG_20171019_130333.jpg

someone tell me how to start programming it?
I have check the connections with microcontroller to find out if its I2C, SPI or UART based but its not. Pins are connected to the normal I/O pins of microcontroller.
Thanks
 

Just do a reverse engineering of the protocol - use scope to record transmission and then guess how to drive the lcd.
 

Hi,

I agree... first you need to find out the meaning of the connector signals, the signal levels and the protocol.
Not that easy.

This seems not to be a dot matrix display. It seems to have a limited number of "symbols" that can be activated or not.

Klaus
 

I agree with Klaus, it is very doubtful that you can use the display for anything other than it's original purpose. The symbols on the LCD are not programmed to look like that, they are manufactured as characters on the LCD glass itself.

Brian.
 

it is very doubtful that you can use the display for anything other than it's original purpose. The symbols on the LCD are not programmed to look like that, they are manufactured as characters on the LCD glass itself.

You are right bitwixt its on LCD glass itself. The LCD is being used in UPS that's why it has custom icons. I also want to use it in the same scenario that's why i have choose this LCD.
 

Hi guys
I have made videos of signals going to LCD.


can anyone tell me how to start decoding the signals?
The Blue waveform is at WR pin of LCD and yellow waveform is at DATA pin of LCD.

Thanks
 

This whole project begs the question, why do this?
1) because you are interested in figuring out how to control this LCD because you think it might be fun.
Might be worthwhile
2) you bought it on ebay really cheap and were hoping to use it in your application.
Not worth the effort, unless you don't care and are really doing this for 1.
3) you like to waste time reverse engineering someone else's product so you can clone it.
This might be worthwhile, but also gets into a grey area of legality.

As you have no datasheet nor any user guide, you will have to capture all the data, not on a scope but all the data for all possible transfers to the LCD using something like a logic analyzer. Then you have to start trying to determine the protocol from all that data, by trying to see if you can figure out what part of the serial data is address and data. Then you will have to determine which bits affect what parts of the LCD screen based on the numerous transfers you've captured.

I expect this may take weeks of work to figure all this out and then you will likely still end up with some mysterious transfers that magically make it work/not_work.
 

Screen shots like those are like seeing a single word from a book and trying to work out the rest.

Signals like those alone mean nothing except that something was sent to the LCD. At the very least you need to know what was happening when the signals were captured. I would suggest you start by capturing the LCD initialization commands to see if they fit the pattern of any of the standard LCD controllers. To do that you need to capture 'E', 'RS' and the data lines simultaneously. An oscilloscope isn't the ideal tool, a logic analyzer is best. The initialization commands will be the first things sent to the LCD when it is first powered up so they should be easy to identify. Typically expect to see as many as 10 commands to prepare the LCD before it is ready to display information.

Brian.
 

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