Enable 1bit SDMMC for Olimex ESP32-EVB

Fixes:
https://github.com/espressif/arduino-esp32/issues/495#issuecomment-31604
2612

libraries/SD_MMC/src/SD_MMC.cpp

@@ -34,7 +34,7 @@ SDMMCFS::SDMMCFS(FSImplPtr impl)
     : FS(impl), _card(NULL)
 {}
 
-bool SDMMCFS::begin(const char * mountpoint)
+bool SDMMCFS::begin(const char * mountpoint, bool mode1bit)
 {
     if(_card) {
         return true;
@@ -43,7 +43,12 @@ bool SDMMCFS::begin(const char * mountpoint)
     sdmmc_slot_config_t slot_config = SDMMC_SLOT_CONFIG_DEFAULT();
     sdmmc_host_t host = SDMMC_HOST_DEFAULT();
     host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;
-    //host.flags = SDMMC_HOST_FLAG_1BIT; //use 1-line SD mode
+#ifdef BOARD_HAS_1BIT_SDMMC
+    mode1bit = true;
+#endif
+    if(mode1bit) {
+        host.flags = SDMMC_HOST_FLAG_1BIT; //use 1-line SD mode
+    }
 
     esp_vfs_fat_sdmmc_mount_config_t mount_config = {
         .format_if_mount_failed = false,

libraries/SD_MMC/src/SD_MMC.h

@@ -28,7 +28,7 @@ protected:
 
 public:
     SDMMCFS(FSImplPtr impl);
-    bool begin(const char * mountpoint="/sdcard");
+    bool begin(const char * mountpoint="/sdcard", bool mode1bit=false);
     void end();
     sdcard_type_t cardType();
     uint64_t cardSize();

variants/esp32-evb/pins_arduino.h

@@ -25,4 +25,6 @@ static const uint8_t MOSI  = 2;
 static const uint8_t MISO  = 15;
 static const uint8_t SCK   = 14;
 
+#define BOARD_HAS_1BIT_SDMMC
+
 #endif /* Pins_Arduino_h */