user can change SPI frequency

Author: LynnL4

src/SD/Seeed_SD.cpp

@@ -19,12 +19,12 @@ extern SD_CardInfo cardinfo; //the cardinfo
 
 namespace fs {
 
-boolean SDFS::begin(uint8_t ssPin, SPIClass &spi)
+boolean SDFS::begin(uint8_t ssPin, SPIClass &spi, int hz)
 {
    card = &cardinfo;
    card->ssPin = ssPin; 
    card->spi = &spi;
-
+   card->frequency = hz;
    spi.begin();
 
    FRESULT status = FR_OK;

src/SD/Seeed_sdcard_hal.cpp

@@ -62,18 +62,18 @@ void SD_CS_LOW(void)
 void SD_HIGH_SPEED_ENABLE(void)
 {
     #ifdef KENDRYTE_K210
-      cardinfo.spi->beginTransaction(SPISettings(4000000, LSBFIRST, 0));
+      cardinfo.spi->beginTransaction(SPISettings(cardinfo.frequency, LSBFIRST, 0));
     #else
-       cardinfo.spi->beginTransaction(SPISettings(4000000, MSBFIRST, SPI_MODE0));
+       cardinfo.spi->beginTransaction(SPISettings(cardinfo.frequency, MSBFIRST, SPI_MODE0));
     #endif
 }
 
 static void SD_HIGH_SPEED_DISABLE(void)
 {
     #ifdef KENDRYTE_K210
-      cardinfo.spi->beginTransaction(SPISettings(200000, LSBFIRST, 0));
+      cardinfo.spi->beginTransaction(SPISettings(400000, LSBFIRST, 0));
     #else
-       cardinfo.spi->beginTransaction(SPISettings(200000, MSBFIRST, SPI_MODE0));
+       cardinfo.spi->beginTransaction(SPISettings(400000, MSBFIRST, SPI_MODE0));
     #endif
 }