LCD Panel - Creating a basic controller board

Thread Starter

ClementVH

Joined May 11, 2020
11
Hello there,

I want to take a dive in electronic by creating a basic controller board for a scavenged LCD panel from a laptop. I couldn't find information about this process online so here I am.

My panel specifications : Link

My question is about the challenges of such a project.
So far I found out that I have to generate a LVDS signal to send to the panel and connect it to power. The LVDS specifications is clear enough that I think I can generate one on a breadboard with some experimenting.

But are there any other thing to do to make it work ?

For example I don't quite understand the power sequence part. Do I have to send it ? or is it managed by the panel ?
 

MrChips

Joined Oct 2, 2009
21,079
This is an advanced project and not a good way to dive in.
Learn to get your toes wet before learning to thread water.

You need to start with a microcontroller prototyping/develoment kit and learn how to flash an LED, the classic "blinky" program before moving on to "Hello World" program.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
This is an advanced project and not a good way to dive in.
Learn to get your toes wet before learning to thread water.

You need to start with a microcontroller prototyping/develoment kit and learn how to flash an LED, the classic "blinky" program before moving on to "Hello World" program.
Hi,

I'm already familiar with blinking an LED, so far I've managed to read/write to an EEPROM on a breadboard with an arduino ( writing an entire 'array' of bytes ).
Next when I will receive a microprocessor I'll make it use the EEPROM.

But in the mean time I wanted to gather more information on the feasibility of my LCD panel project.
 

MrChips

Joined Oct 2, 2009
21,079
This is still a very advanced project. You would be more successful using an LCD screen designed to work with Arduino boards. These would have library codes already written in order to put data to the screen.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
This is still a very advanced project. You would be more successful using an LCD screen designed to work with Arduino boards. These would have library codes already written in order to put data to the screen.
Of course but I'm not interested in that kind of project. Where is the challenge ? It looks very straight forward. with millions of tutorials about it.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
But never mind about my potential failure on this project, do you know what has to be done in order to make it work ?

Example: the power sequence ?
 

Thread Starter

ClementVH

Joined May 11, 2020
11
Sure, but I need more information and I think that a forum is a good place to gather them.

Do you know if one would need to send the power sequence described in the datasheet to light up a LCD panel ?
 

jpanhalt

Joined Jan 18, 2008
9,386
Sure, but I need more information and I think that a forum is a good place to gather them.

Do you know if one would need to send the power sequence described in the datasheet to light up a LCD panel ?
What more information do you need? As Mr. Chips said, it is in the datasheet. Power on sequence is on or about page 17.

... described in the datasheet to light up a LCD panel
LCD's do not inherently generate light. In this case, the backlight is provided by LED's. Those are described earlier in the manual. I did not read it carefully, but in many cases, turning on the backlight is like a simple switch. However, many LCD's can be read without the backlight on, if the room lighting is good. In fact, in my current project, the backlight draws about 100 mA (yours draws about twice that), so I keep the backlight off most of the time when running from a battery. You can still see changes on the screen. Then when it is turned on, brightness is controlled by the MCU using PWM.

Have you searched the manufacturer's site for application notes? They might give give a flowchart for the POR.
 

jpanhalt

Joined Jan 18, 2008
9,386
Have you ever worked with an HD44780or ST7xxx controller? If not, which controllers have you worked with?

The top part of 6.4 is apparently the power on sequence, that is, the sequence that should be followed for power on and power off. The bottom of that page seems to show how to initialize the screen. The datasheets for the controllers I mention above are explicit on the commands that need to be sent to initialize the display. Maybe yours has a simpler sequence. That's where an application note will help, particularly if you have had experience with those other display controllers.

You have a sophisticated screen that I have not used, nor does it seem Mr. Chips has either. Maybe someone here has used that exact screen. If not, you are going to have to be comfortable writing code for it after you find out what "it" is. Check out pages 20-21 and page 30 and later for what "it" is for the ST7567 controller: https://www.crystalfontz.com/controllers/Sitronix/ST7567/ or pages 36-38 and 49 and later here: https://www.mikrocontroller.net/attachment/343874/ST7567A_V1.2a.pdf
 

Thread Starter

ClementVH

Joined May 11, 2020
11
Oh I see,

No I have no experience with these controllers.

And I can't find more info on this panel indeed.

I have an other panel with this datasheet : Link

It has more infos on the timings for the power on/of sequences
1589289752199.png

Do you think this is enough informations ?
 

jpanhalt

Joined Jan 18, 2008
9,386
Power on and off is a different process than initializing the LCD. One is like starting or stopping the engine in a car; the other is putting it into the proper gear, backing up, changing gears and going somewhere, to use a poor analogy.

Here is the sequence for the HD44780 (a very common controller):
1589290547719.png

That could easily be made smaller, like the bottom of Figure 6.4. I am not sure that is complete, but it has a sequence that one follows AFTER power up. Remember, the controller(s) for your display is/are MCU's too. They need to be initialized, not just turned on with a switch. Many times you will also need to initialize the display memory, or the screen will come up with garbage on it. With LCD's, that garbage will stay until it is written over. So, I initialize my screen by writing 0x00 to every byte in that memory.

This discussion certainly supports the need for you to get familiar with a simpler display before trying to write a controller for a complicated graphical display. Having copied and loaded a library for an arduino to run a character display is not enough.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
I don't quite understand,

You are telling me that the panel needs me to send data over the LVDS connector to initialize the MCU built-in the panel ? Where on the datasheet of the panel is written which MCU is behind the connector and the format of that data ?

Thanks for your replies so far, I feel like I'm learning :).

What display could be simpler yet harder than a character LCD display ?
 

Thread Starter

ClementVH

Joined May 11, 2020
11

dendad

Joined Feb 20, 2016
3,517
I think you may be best served by just purchasing a monitor.
Or, if you want to get a controller board for your LCD, first look carefully to see if you can figure out if it will drive your LCD. And don't forget you will need to add a back light driver. It may not be a simple thing to get going. But then again, it could be if you can find the correct drive board. Then you will need an enclosure and power supply.
A monitor sounds good to me. A lot easier anyway.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
I think you may be best served by just purchasing a monitor.
Or, if you want to get a controller board for your LCD, first look carefully to see if you can figure out if it will drive your LCD. And don't forget you will need to add a back light driver. It may not be a simple thing to get going. But then again, it could be if you can find the correct drive board. Then you will need an enclosure and power supply.
A monitor sounds good to me. A lot easier anyway.
I'm sorry but you are missing the point of my thread here. I want to create a simple controller board for my panel, to learn about electronics.
My goal is to light up this panel and make it display a simple testing pattern like black lines or event just flat red.
 

Thread Starter

ClementVH

Joined May 11, 2020
11
You might be able to cobble something using a PIC with a Integrated Graphics Controller but I don't think you really understand the complexity of the process.
http://ww1.microchip.com/downloads/en/appnotes/01368a.pdf
http://l1demo.org/wiki/_media/39731a.pdf
https://github.com/MicrochipTech/mla_gfx/blob/master/framework/driver/gfx/src/drv_gfx_da210.c
Indeed there is something I don't understand. The panels that I have, come from old laptops and the only connector available is LVDS. Also, there is already a board on the display itself that probably house a lot of logic. My assumption was that this board is already taking care of what you mentioned above, or at least par of it. Tell me if I'm wrong but I think with my panels, I just need few steps to make them work:
  1. plug them to power ( voltage depends on the panel )
  2. plug the LED power ( voltage depends on the panel )
  3. Send a pulse for settings the brightness of the backlight
  4. generate suitable LVDS signal over 3 channels for the colors of each pixels ( can be all '1' to make it white )
  5. Manage the h_sync, v_sync, and all the blanking signals ( maybe not, I saw that one of the panel doesn't even need the h_sync, v_sync )
  6. And the clock signal

What do you think ?
 
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