Very Slow speed using RA8875, SD Card and Arduino Mega


I have been working on a project which requires 7inch touch screen driven by Arduino Mega. I have bought the same from ( 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.

Best regards
Anuj Garg

Please don’t duplicate posts. You already have responses to the same question in the older post that you resurrected.