Add SDIO support to SD snf SDFS, document, example

earlephilhower · Jan 17, 2025 · f48f5e8 · f48f5e8
1 parent db8e44e
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Showing 4 changed files with 67 additions and 19 deletions.
diff --git a/docs/fs.rst b/docs/fs.rst
@@ -174,6 +174,23 @@ second SPI port, ``SPI1``.  Just use the following call in place of
 
     SD.begin(cspin, SPI1);
 
+Enabling SDIO operation for SD
+------------------------------
+SDIO support is available thanks to SdFat implementing a PIO-based SDIO controller.
+This mode can significantly increase IO performance to SD cards but it requires that
+all 4 DAT0..DAT3 lines to be wired to the Pico (most SD breakout boards only provide
+1-but SPI mode of operation).
+
+To enable SDIO mode, simply specify the SD_CLK, SD_CMD, and SD_DAT0 GPIO pins.  The clock
+and command pins can be any GPIO (not limited to legal SPI pins).  The DAT0 pin can be any
+GPIO with remaining DAT1...3 pins consecutively connected.
+
+..code:: cpp
+
+    SD.begin(RP_CLK_GPIO, RP_CMD_GPIO, RP_DAT0_GPIO);
+
+No other changes are required in the application to take advantage of this high
+performance mode.
 
 Using VFS (Virtual File System) for POSIX support
 -------------------------------------------------

diff --git a/libraries/SD/examples/CardInfo/CardInfo.ino b/libraries/SD/examples/CardInfo/CardInfo.ino
@@ -37,6 +37,12 @@ const int _MOSI = 7;  // AKA SPI TX
 const int _CS = 5;
 const int _SCK = 6;
 
+// If you have all 4 DAT pins wired up to the Pico you can use SDIO mode
+const int RP_CLK_GPIO = -1; // Set to CLK GPIO
+const int RP_CMD_GPIO = -1; // Set to CMD GPIO
+const int RP_DAT0_GPIO = -1; // Set to DAT0 GPIO. DAT1..3 must be consecutively connected.
+
+
 // include the SD library:
 #include <SPI.h>
 #include <SD.h>
@@ -54,21 +60,26 @@ void setup() {
   Serial.println("\nInitializing SD card...");
 
   bool sdInitialized = false;
-  // Ensure the SPI pinout the SD card is connected to is configured properly
-  // Select the correct SPI based on _MISO pin for the RP2040
-  if (_MISO == 0 || _MISO == 4 || _MISO == 16) {
-    SPI.setRX(_MISO);
-    SPI.setTX(_MOSI);
-    SPI.setSCK(_SCK);
-    sdInitialized = SD.begin(_CS);
-  } else if (_MISO == 8 || _MISO == 12) {
-    SPI1.setRX(_MISO);
-    SPI1.setTX(_MOSI);
-    SPI1.setSCK(_SCK);
-    sdInitialized = SD.begin(_CS, SPI1);
+  if (RP_CLK_GPIO >= 0) {
+    // No special requirements on pin locations, this is PIO programmed
+    sdInitialized = SD.begin(RP_CLK_GPIO, RP_CMD_GPIO, RP_DAT0_GPIO);
   } else {
-    Serial.println(F("ERROR: Unknown SPI Configuration"));
-    return;
+    // Ensure the SPI pinout the SD card is connected to is configured properly
+    // Select the correct SPI based on _MISO pin for the RP2040
+    if (_MISO == 0 || _MISO == 4 || _MISO == 16) {
+      SPI.setRX(_MISO);
+      SPI.setTX(_MOSI);
+      SPI.setSCK(_SCK);
+      sdInitialized = SD.begin(_CS);
+    } else if (_MISO == 8 || _MISO == 12) {
+      SPI1.setRX(_MISO);
+      SPI1.setTX(_MOSI);
+      SPI1.setSCK(_SCK);
+      sdInitialized = SD.begin(_CS, SPI1);
+    } else {
+      Serial.println(F("ERROR: Unknown SPI Configuration"));
+      return;
+    }
   }
 
   if (!sdInitialized) {

diff --git a/libraries/SD/src/SD.h b/libraries/SD/src/SD.h
@@ -36,11 +36,17 @@ class SDClass {
         SDFS.setConfig(SDFSConfig(csPin, SPI_HALF_SPEED, spi));
         return SDFS.begin();
     }
+
     bool begin(uint8_t csPin, uint32_t cfg = SPI_HALF_SPEED, HardwareSPI &spi = SPI) {
         SDFS.setConfig(SDFSConfig(csPin, cfg, spi));
         return SDFS.begin();
     }
 
+    bool begin(uint8_t clkPin, uint8_t cmdPin, uint8_t dat0Pin, uint32_t cfg = SD_SCK_MHZ(50)) {
+        SDFS.setConfig(SDFSConfig(clkPin, cmdPin, dat0Pin, cfg));
+        return SDFS.begin();
+    }
+
     void end(bool endSPI = true) {
         SDFS.end();
         if (endSPI && _spi) {

diff --git a/libraries/SDFS/src/SDFS.h b/libraries/SDFS/src/SDFS.h
@@ -45,7 +45,8 @@ class SDFSConfig : public FSConfig {
 public:
     static constexpr uint32_t FSId = 0x53444653;
 
-    SDFSConfig(uint8_t csPin = 4, uint32_t spi = SD_SCK_MHZ(10), HardwareSPI &port = SPI) : FSConfig(FSId, false), _csPin(csPin), _part(0), _spiSettings(spi), _spi(&port)  { }
+    SDFSConfig(uint8_t csPin = 4, uint32_t spi = SD_SCK_MHZ(10), HardwareSPI &port = SPI) : FSConfig(FSId, false), _sdio(false), _clkPin(255), _csPin(csPin), _cmdPin(255), _dat0Pin(255), _part(0), _spiSettings(spi), _spi(&port)  { }
+    SDFSConfig(uint8_t clkPin, uint8_t cmdPin, uint8_t dataPin, uint32_t spi = SD_SCK_MHZ(10)) : FSConfig(FSId, false), _sdio(true), _clkPin(clkPin), _cmdPin(cmdPin), _dat0Pin(dataPin), _part(0), _spiSettings(spi), _spi(nullptr)  { }
 
     SDFSConfig setAutoFormat(bool val = true) {
         _autoFormat = val;
@@ -69,7 +70,11 @@ class SDFSConfig : public FSConfig {
     }
 
     // Inherit _type and _autoFormat
+    bool      _sdio;
+    uint8_t   _clkPin;  // SDIO only;
     uint8_t   _csPin;
+    uint8_t   _cmdPin;  // SDIO only
+    uint8_t   _dat0Pin; // SDIO only
     uint8_t   _part;
     uint32_t  _spiSettings;
     HardwareSPI *_spi;
@@ -131,11 +136,20 @@ class SDFSImpl : public FSImpl {
         if (_mounted) {
             return true;
         }
-        SdSpiConfig ssc(_cfg._csPin, SHARED_SPI, _cfg._spiSettings, _cfg._spi);
-        _mounted = _fs.begin(ssc);
-        if (!_mounted && _cfg._autoFormat) {
-            format();
+        if (!_cfg._sdio) {
+            SdSpiConfig ssc(_cfg._csPin, SHARED_SPI, _cfg._spiSettings, _cfg._spi);
             _mounted = _fs.begin(ssc);
+            if (!_mounted && _cfg._autoFormat) {
+                format();
+                _mounted = _fs.begin(ssc);
+            }
+        } else {
+            SdioConfig ssc(_cfg._clkPin, _cfg._cmdPin, _cfg._dat0Pin);
+            _mounted = _fs.begin(ssc);
+            if (!_mounted && _cfg._autoFormat) {
+                format();
+                _mounted = _fs.begin(ssc);
+            }
         }
         FsDateTime::setCallback(dateTimeCB);
         return _mounted;