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I have had this LCD lying on my shelf for the past few years and have not been able to figure out how to use it. It is an LCD from the printer Epson TX710W. I searched for a datasheet, but I couldn't find one. The back of the board contains nothing but traces, the whole module has no ICs on it, I think that's all built into the LCD itself. I don't have the original board that the LCD module connects to.

Could someone tell me how to control this with an Arduino? If that is not possible, could you at least point me in the right direction? What communication protocol does it use?

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    \$\begingroup\$ How much do you really value your time and how much will it cost to buy one that has full design details in a data sheet? \$\endgroup\$
    – Andy aka
    Feb 15, 2018 at 11:16
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    \$\begingroup\$ Without a data sheet, or someone here who knows exactly what it is, how to drive it, and the willingness to document it, you're likely to be out of luck. \$\endgroup\$
    – Colin
    Feb 15, 2018 at 11:17
  • \$\begingroup\$ @Andy aka Yeah I know I can just buy one, I want to do this for the education experience. \$\endgroup\$
    – skillz21
    Feb 15, 2018 at 11:20
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    \$\begingroup\$ @Colin__s Can't you figure out the protocol using the grouping on the ribbon cable? Or something similar? \$\endgroup\$
    – skillz21
    Feb 15, 2018 at 11:20
  • \$\begingroup\$ Education: don't use devices that don't have a data sheet unless you know how to use them. I don't know how many times I've said these basic words.... \$\endgroup\$
    – Andy aka
    Feb 15, 2018 at 11:24

2 Answers 2

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Well there are some things that may be deduced from the two pics you provided. What follows is just what I think about your module and it would be amazing if it was true. Do not take it as correct.

Let's focus on your CN1 connector, the black one. Since this screen needs to be driven by something apart, I would say that connector is the interface to be connect with a microcontroler.

Let's focus on the tracks connected to the back of the CN1 connector (soldered) :

  • PIN 1 & 2 : Probably the power supply of the module (VCC). I say that because of the apparent tracks width and because of what comes next.
  • PIN 4, 9 & 11 : This is GND since the copper connected covers the most of the PCB surface (it is common).
  • PIN 3, 5, 6, 7, 8 & 10 : Those are signals (see how the tracks width is much thinner than the power supply ones).

Two main questions comes to the mind :

  1. What is the power supply voltage to be used ?
  2. What is the protocol used to drive the LCD ?

For the first question, well, generally the voltage used to drive this kind of LCD screen is either 3.3V or 5V. You can try first 3.3V to see if the backlight lights up. If not, try 5V. But be careful ! Maybe one of the signal track is used to enable the backlight (so it won't work even with the proper voltage applied if the backlight enable is not driven correctly).

For the second question... I would bet on SPI interface. Why ? Well, first of all, when it comes to drive a LCD screen with this size, SPI interface can be used. Moreover, there are 6 tracks used as signals type. If this is indeed SPI, 4 tracks are used :

  1. Chip Select ;
  2. MISO ;
  3. MOSI ;
  4. CLK.

This let us 2 signals left.

I have read some datasheets of SPI LCD screen, it is common to find a RESET pin. So, since I am a good player, I'll bet on a RESET signal for the LCD.

1 signal left. I don't really know what it could be used for. Maybe a Backlight Enable command as stated previously ? To be sure, It would be useful to test this screen on the printer to see if it was possible to turn on/off the LCD or to dim it.

Now is the following issue : let's assume it is the correct interface (SPI). Which PIN number is associated with what function ? I have no idea and that's where you will be stuck from. Actually, and this is just an assumption, but since PIN 5, 6, 7 & 8 are routed together (not separated by ground plane like it is for PIN 3 & 10), I would say it is the SPI interface. PIN 3 is either the RESET command or Backlight Enable (if Backlight Enable command there is). Now that we are quite sure about the power supply tracks, you can still try to switch HIGH/LOW some signal traces in the first place to see what happens. But as I said before : Be careful

In any cases, without the datasheet it will be very very difficult to display something. You can still reverse the PCB routing. Will it be useful ? I don't really know.

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    \$\begingroup\$ I agree with your deductions. The screen appears to be a monochrome COG type. The interface protocols on these are quite standard. If they can determine the screen dimensions in pixels, they should be able to narrow down the driver chip being used. Getting a datasheet for similar screens should provide clues about the relative routing order of the SPI pins, since these are largely fixed by the COG pinout. They should be able to figure out the backlight control pin from the board routing. \$\endgroup\$
    – Jon
    Feb 15, 2018 at 14:31
  • \$\begingroup\$ Some LCDs have a Data/Command pin to select the mode where the data will go (to a set of registers controlling the display settings or directly to the frame buffer). \$\endgroup\$
    – Arsenal
    Feb 15, 2018 at 14:51
  • \$\begingroup\$ @Jon No actually, it was a colour display. \$\endgroup\$
    – skillz21
    Feb 15, 2018 at 21:14
  • \$\begingroup\$ The PCB says CMYK on it.... could that be a clue as to what protocol it uses? \$\endgroup\$
    – skillz21
    Feb 15, 2018 at 21:15
  • \$\begingroup\$ Don't think so. CMYK means Cyan Magenta Yellow Key (Black). It is a specific color format for printer. \$\endgroup\$
    – vionyst
    Feb 15, 2018 at 22:42
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I am afraid you are out of luck!

Without the datasheet you have no way of knowing how to properly power the display. How to drive the backlight (LED configuration, recommended limits, etc), what controller is inside the display (which is what you will actually communicate with to control it (example is ST7789V, there are a handful of those) and how it is configured (it can be RGB or a MPU i8080 interface). Sometimes the display manufacturer locks the interface into a single mode, other times they allow you to select it. There is no standard here.

I would say there is no educational value, or highly inefficient one at the very best trying to reverse engineer and operate this display.

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  • \$\begingroup\$ The PCB says CMYK on it.... could that be a clue as to what protocol it uses? \$\endgroup\$
    – skillz21
    Feb 15, 2018 at 21:05

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