SD:

- optimize SPI usage 148% write speed (24kB/s -> 37kB/s) and 127% read speed (121kB/s -> 155kB/s) at 8MHz
 - add clock frequency as parameter for begin(csPin, frequency)
 - SD @80MHz write: 84kB/s read: 231kB/s

SPI add functions:
 - void write32(uint32_t data);
 - void write32(uint32_t data, bool msb);
 - void transferBytes(uint8_t * out, uint8_t * in, uint32_t size);

Adafruit_ILI9341:
 - code clean

libraries/SD/src/SD.cpp

@@ -326,13 +326,7 @@ boolean callback_rmdir(SdFile& parentDir, char *filePathComponent,
   return true;
 }
 
-
-
-/* Implementation of class used to create `SDCard` object. */
-
-
-
-boolean SDClass::begin(uint8_t csPin) {
+boolean SDClass::begin(uint8_t csPin, uint32_t sckRateID) {
   /*
 
     Performs the initialisation required by the sdfatlib library.
@@ -340,13 +334,11 @@ boolean SDClass::begin(uint8_t csPin) {
     Return true if initialization succeeds, false otherwise.
 
    */
-  return card.init(SPI_HALF_SPEED, csPin) &&
+  return card.init(sckRateID, csPin) &&
          volume.init(card) &&
          root.openRoot(volume);
 }
 
-
-
 // this little helper is used to traverse paths
 SdFile SDClass::getParentDir(const char *filepath, int *index) {
   // get parent directory