I have been working on a project which requires 7inch touch screen driven by Arduino Mega. I have bought the same from buydisplay.com ( Serial SPI Arduino 7"TFT LCD Touch Shield RA8875 for Mega/Due/Uno ).
I have plugged in the screen+shield+mega and uploaded the sample code and it worked fine. Thereafter I googled several different libraries and samples (mostly using Adafruit library) and all worked fine at a basic level.
However here is a problem which I want someone to please help me with. When I am trying to display a BMP (800x480) on the screen from the SD card it is taking around 20seconds to load a single image on the screen. As you can see this much speed is of no good for any practical application.
I am using example code at ( Adafruit_RA8875/examples/ra8875_bitmap at master · adafruit/Adafruit_RA8875 · GitHub )
So my question is that if RS8875 is the bottle neck or SPI is the bottle neck? Because if RA8875 is the bottle neck then I have to look at other options. But if SPI is the bottle neck then will Parallel interface increase the speed? And if yes then anyone have a basic library?
PS: I have converted all the digitalwrite in ra8875 library as well in the native SPI library to direct port manipulation and that did not helped at all.