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I have been using LCD screens (with the controllers) for my projects for a long time. Now I thought of learning how these screens actually work, the part before they go to the controllers.

Well the idea came to my mind when I managed to scavenge an old working screen out of my old tablet. It has 60 pins and I managed to find a datasheet for it. The model number is: AU OPTRONICS A080SN03 (datasheet here).

What does each pin of a 60 pin TFT display do? And how can I use it?

David
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Nilanjan
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  • @RogerRowland yeah it maybe can be called a datasheet cause it atleast has some data about the pinouts, some schematics for power and signals... – Nilanjan Dec 24 '14 at 07:22
  • the only think i want is understanding the pinouts, what they mean and moreover how to use them... do you think u have some help for me? – Nilanjan Dec 24 '14 at 07:24
  • @Nilanjan Sorry, I could read the pdf like you could, but I wouldn't be able to add anything beyond that. – Roger Rowland Dec 24 '14 at 07:31
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    @RogerRowland I was wrong, I thought that the preview was all there was. – Nick Alexeev Dec 24 '14 at 08:53

2 Answers2

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The datasheet seems pretty thorough, and the core functionality looks pretty straightforward. Once everything is set up, you clock in RGB values one pixel at a time. First you go across a row, then down a column.The relevant control signals are:

DR[7:0] - 8-bit red value for the current pixel

DG[7:0] - 8-bit green value for the current pixel

DB[7:0] - 8-bit blue value for the current pixel

DCLK - When this goes high, the pixel data is latched. When it goes low, the LCD switches to the next horizontal pixel

DE - When this is high, pixel data can be latched. I think when it goes low the LCD switches to the next row, but I'm not sure whether it's independent of DCLK.

U/D - Selects whether to go up or down a row when DE toggles

R/L - Selects whether to go left or right a pixel when DCLK toggles

So the basic flow will be (from the start of the first row)

Initial conditions: DE=1, DCLK=0

Step 1: Set the RGB values for the pixel via DR, DG, and DB.

Step 2: Drive DCLK high to latch the RGB values.

Step 3: Drive DCLK low to select the next pixel in the row.

Step 4: Repeat steps 1-3 800 times total to set every pixel in the row.

Step 5: Drive DE low to select the next row.

Step 6: Drive DE high to enable pixel writes.

Step 7: Repeat steps 1-6 600 times total to cover every row.

There are lots of timing constraints on these steps. Section 5 has the specs for those.

There are some other control signals, voltage references, and a serial interface. I'm not sure what the serial interface is for, but I didn't look very thoroughly. None of them looks terribly complicated.

All that being said, using this LCD will be very difficult. This is a complex mixed-signal system. Plus, as described in section 4a, you need six separate voltage supplies. There are some example schematics for switching regulators in section G, but each of those is a project in itself.

Studying the datasheet could be very educational, but I don't recommend this as a project for a beginner.

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Adam Haun
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  • Thanks a lot, ya i can understand that its a complex project but i am ready to take it up. This part is mostly cleared but what i still cannot understand is why are so many power sources needed and why is the gamma correction voltage refference needeed. – Nilanjan Dec 24 '14 at 10:37
  • Lots of oddball voltage are needed because the LCD chemistry is analog, and quirky. All LCDs require lots of oddball waveforms, it's just most pre-packaged LCDs generate the voltages internally. – Connor Wolf Dec 24 '14 at 11:06
  • Gamma correction is a nonlinear brightness correction that tries to match the display to the human eye. I suppose if you wanted to be really fancy, you could make those voltages adjustable. I'd start with the recommended ones, though. – Adam Haun Dec 24 '14 at 17:59
  • @Adam Huan Ok, thats understandable but why so many pins for that? – Nilanjan Dec 25 '14 at 04:08
  • My guess is that they have some sort of comparator network set up for the gamma adjustment. Probably they need a lot of reference voltages because each color has 256 brightness levels. – Adam Haun Dec 25 '14 at 05:36
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check out this chip which I have seen used on a board that controls that exact tft display: THC63LVD104C

CMB
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