Warning: This version has major internal changes.

SdFat version 2.3.0 has major changes to implement RP2040/RP2350 SDIO.

In addition there a number of bug fixes.

Begin by running the Rp2040SdioSetup example to try RP2040/RP2350 SDIO.

This example requires a SDIO Card socket with the following six lines.

CLK - A clock signal sent to the card by the MCU. CMD - A bidirectional line for for commands and responses. DAT[0:3] - Four bidirectional lines for data transfer.

CLK and CMD can be connected to any GPIO pins. DAT[0:3] can be connected to any four consecutive GPIO pins in the order DAT0, DAT1, DAT2, DAT3.

Here is an example of SDIO for Pico using an Adafruit socket, PiCowbell Proto and PiCowbell Proto Doubler.

This Socket supports SDIO with:

#define RP_CLK_GPIO 10
#define RP_CMD_GPIO 11
#define RP_DAT0_GPIO 12  // DAT1: GPIO13 DAT2: GPIO14, DAT3: GPIO15.

It also can be used on SPI1 with:

const uint8_t SD_CS_PIN = 15;
#define SD_CONFIG SdSpiConfig(SD_CS_PIN, DEDICATED_SPI, SPI_CLOCK, &SPI1)

  // In setup
  SPI1.setSCK(10);
  SPI1.setTX(11);
  SPI1.setRX(12);

The release version of SdFat Version 2 is here:

https://github.com/greiman/SdFat

This library is in development, features may change and it may have bugs. I am posting this version to get comments and help finding bugs/compatibility problems.

You can help by posting issues for problems you find. I am doing a great deal of testing but actual applications make the best test cases.

SdFat Version 2 supports FAT16/FAT32 and exFAT SD cards. It is mostly backward compatible with SdFat Version 1 for FAT16/FAT32 cards.

exFAT supports files larger than 4GB so files sizes and positions are type uint64_t for classes that support exFAT.

exFAT has many features not available in FAT16/FAT32. exFAT has excellent support for contiguous files on flash devices and supports preallocation.

If the SD card is the only SPI device, use dedicated SPI mode. This can greatly improve performance. See the bench example.

Here is write performance for an old, 2011, card on a Due board.

Shared SPI:
write speed and latency
speed,max,min,avg
KB/Sec,usec,usec,usec
294.45,24944,1398,1737

Dedicated SPI:
write speed and latency
speed,max,min,avg
KB/Sec,usec,usec,usec
3965.11,16733,110,127

The default version of SdFatConfig.h enables support for dedicated SPI and optimized access to contiguous files. This makes SdFat Version 2 slightly larger than Version 1. If these features are disabled, Version 2 is smaller than Version 1.

The types for the classes SdFat and File are defined in SdFatConfig.h. The default version of SdFatConfig.h defines SdFat to only support FAT16/FAT32. SdFat and File are defined in terms of more basic classes by typedefs. You can use these basic classes in applications.

Support for exFAT requires a substantial amount of flash. Here are sizes on an UNO for a simple program that opens a file, prints one line, and closes the file.

FAT16/FAT32 only: 9780 bytes flash, 875 bytes SRAM.

exFAT only: 13830 bytes flash, 938 bytes SRAM.

FAT16/FAT32/exFAT: 19326 bytes flash, 928 bytes SRAM.

The section below of SdFatConfig.h has been edited to uses FAT16/FAT32 for small AVR boards and FAT16/FAT32/exFAT for all other boards.

/**
 * File types for SdFat, File, SdFile, SdBaseFile, fstream,
 * ifstream, and ofstream.
 *
 * Set SDFAT_FILE_TYPE to:
 *
 * 1 for FAT16/FAT32, 2 for exFAT, 3 for FAT16/FAT32 and exFAT.
 */
#if defined(__AVR__) && FLASHEND < 0X8000
// FAT16/FAT32 for 32K AVR boards.
#define SDFAT_FILE_TYPE 1
#else  // defined(__AVR__) && FLASHEND < 0X8000
// FAT16/FAT32 and exFAT for all other boards.
#define SDFAT_FILE_TYPE 3
#endif  // defined(__AVR__) && FLASHEND < 0X8000

The SdBaseFile class has no Arduino Stream or Print support.

The File class is derived from Stream and SdBaseFile.

The SdFile class is derived from SdBaseFile and Print.

Please try the examples. Start with SdInfo, bench, and ExFatLogger.

To use SdFat Version 2, unzip the download file, rename the library folder SdFat and place the SdFat folder into the libraries sub-folder in your main sketch folder.

For more information see the Manual installation section of this guide:

http://arduino.cc/en/Guide/Libraries

A number of configuration options can be set by editing SdFatConfig.h define macros. See the html documentation File tab for details.

Please read the html documentation for this library in SdFat/doc/SdFat.html. Start with the Main Page. Next go to the Classes tab and read the documentation for the classes SdFat32, SdExFat, SdFs, File32, ExFile, FsFile.

The SdFat and File classes are defined in terms of the above classes by typedefs. Edit SdFatConfig.h to select class options.

Please continue by reading the html documentation in the SdFat/doc folder.