I have a CPU board that interfaces to a standard 16x2 chars display, based on HD44780 controller.
I'd like to replace this display with a full-color big TFT display, maybe 10", but I can't change the firmware of the CPU (because I don't have the source code and I can't rewrite it, because of cost and time).
The simple idea is to create an interface between the current CPU board and the TFT display. This interface should be able to detect the signals from the CPU and that was directed to HD44780, interpret the instructions (write CGRAM/DDRAM and so on) and write the same things to the big TFT display.
Of course, exactly the same texts will be written on TFT display (of course with a bigger and visible font) and this is acceptable.
So the MCU on the interface should be able to read 8 data bits, RS and R/W signals syncronous to signal E.
I'm thinking to configure E signal as an external interrupt on the falling edge. In the interrupt, I read data bits, R/W and RS and decode the instruction or data.
Any suggestions? Maybe a similar code is already online.