Over the years, I've accumulated numerous LCD panels and controller boards salvaged from TVs, Monitors, Cell Phones, digital picture frames, GPS devices and tablets. I would like to reuse the panels with the discrete controllers in my electronics projects.
I may have some proprietary panel and controller configurations, but I presume the vast majority are just stock. Is there a "rule of thumb" or a specification list for determining the compatibility of a controller with an LCD panel?
The way to interface to these is sheer will and a lot of skill. You will need an oscilloscope.
There is no specification list, because the amount of devices you have could include several ranges of manufacturers and technologies.
If the controller is on the back of the LCD, then you are in luck. If it's not, then you will have to find an equivalent LCD controller and design a PCB with a microcontroller on it.
The first thing to do is find the datasheet for the LCD controller chip, without this you have a real uphill battle. If you know the manufacturer and find the package this might help you reverse engineer your module. Some companies only provide datasheets on request, some you have to have an agreement with them.
If what you have salvaged is an LCD module that is manufactured, this will be easier to interface to as the manufacturer will in all likely hood have the datasheet and drivers.
Once you have found the datasheet, you can then figure out how to interface to it. The LCD controller will either be a parallel (for the bigger screens with a faster update) or a serial (smaller screens with a slower update). Some of the serial screens use SPI. The parallel ones will have data and address lines and control lines similar to writing to memory.
Check the timing in the datasheet, if you needs speeds more than 40Mhz this may be difficult to prototype. If you need impedance controlled lines these will be more difficult to prototype and you may need a network analyzer.
Then connect your microprocessor to the data (and or address lines) and see if you can access a register and read and write data to the LCD (preferably control registers to test communication).
The last step will be writing drivers, the manufacturer may be generous and provide some C code to make it so you don't have to write the drivers from scratch.
Here are some links to help get a feel for how this is done for different displays:
TFT hacking discussion
Epson LCD hack
Reverse engineering character LCD display
Remember that to implement one interface to an LCD can take man months of time to implement for a product, a project like this can really help you appreciate economies of scale.
