Sildenafile

With the aid of a logic analyzer I Have found that the chip select signal was coming from another pin than the expected.

Now the SD card is working.

It took me a long run to adapt the code, but I could finally boot in on the Blue Pill.

Steps involed:

• Download and install STM32 duino
• Include directives for every hardware dependent instruction (same code can still be compiled to Mega328 based Arduino) 
• Fiddle with one configuration defitinion for SDFat library
• Adapt the code to compile for newer PCD8455 display library