Reverse Engineering LCD Displays

Dorkbot logo on a large LCD display

Over at DorkbotPDX in Portland, a member showed up with a stack of large LCD displays from point of sale terminals. [Paul] took it upon himself to reverse engineer the displays so that they can be recycled in future projects.

The control circuit for this LCD resides on a rather large PCB with quite a variety of components. The board was reduced to three main components: an MSM6255 display controller, a 32k RAM chip which is used as the framebuffer, and a tri-state driver.

With all the unneeded components out of the way, a custom board based around an ATmega88 MCU was added. This board was soldered in to interface with the LCD controller’s bus. This allows data to be written from the 128k flash ROM on the custom board into the frame buffer. Once this is done, the display controller will display the data on the LCD.

Now that data could be written, [Paul] figured out the correct configuration for the display controller. That was the final piece in getting images to show up correctly on the display. If you happen to find some old Micros 2700 POS terminals, [Paul]’s detailed write-up will help you scavenge the displays.

9 thoughts on “Reverse Engineering LCD Displays

  1. Nice one, and a really detailed write up indeed :)

    I… I no. I can’t stop myself from nitpicking:
    Please don’t write LCD displays. Nobody put a display in your display, so you can display while you display or something.

        1. LCD module! Since it’s not only the panel itself, but also control electronics packaged in a modular housing for ease of installation and replacement.

    1. Are liquid crystal LCD displays those things on ATM machines that help you put in your PIN number to get cash money?

      1. Yes, that’s right! But this one is from a point-of-sale POS machine and has been connected to a new PCB board (with RAM memory).

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