I'm going to develop a project where a small 2.4" TFT display module with resistive touch panel will be used.
I'd like to use free emWin libraries distributed from NXP or ST for their Cortex-M3/M4 MCUs.
At first, I was thinking to use MCUs with integrated TFT controller that would drive "directly" the display through RGB interface (vsync, hsync, dotclock, red, green, blue). The problem arrived when I started finding a suitable display: it's very difficult to find a small 2.4" TFT with RGB interface. Most of them provide only a parallel 8/16-bits MPU interface.
I think because, at small sizes, the parallel MPU interface is generally sufficient for most applications, where the graphics aren't too complex. So the RGB interface isn't necessary.
Parallel MPU interface could save me an external SDRAM for framebuffer (with parallel interface, the framebuffer is inside the external TFT controlle) and simplify the PCB. I'm not able to understand if the parallel bandwidth is sufficient for my application, but I'd like to give it a try.
I have two questions related to drive the TFT module through parallel interface.
The first: are emWin libraries released by NXP (and ST) compatible with parallel interface? The original product (from Segger) is surely compatible, but it's not clear to me if the compiled version released by NXP (or ST) is compatible. I worry the compiler library could work only with RGB interface.
The second question: should the MCU have an external memory bus for interfacing the display? I know I can use a generic GPIO port as the parallel port for the display, but I think the performance won't be good. I think it should be better to interface the parallel port of TFT to the external memory bus of the MCU. In this case, I'm not sure how to make a good connection, how to manage all the signals (chip select, write enable, read enable, ...). Do you know any demo board with such kind of connection with publicly available schematics?