Teensy 4.1 SDIO direct multi-sector reads, no FAT

J

jammux

New member
Hoping someone can get me started. As post title says, I wish to perform multi-sector (either 4, 8 or 16) SDIO reads directly to memory using Teensy 4.1. I don't need FAT file system support. Looking at the code in SdioTeensy.cpp, it looks as though some multi-sector read requests end up simply doing "n" single sector reads, which is not what I want. How to I make sure that when I read more than one sector, it's only a single SD operation? Also, not sure where to start since FAT support seems interwoven into the SdFat code, and I just want to read sectors directly. Thanks.
 
I would look at the BlockDeviceInterface or in current version FsBlockDeviceInterface and see if it works for you.

The header file has a few different read operations available:
Code: 
  /**
   * Read a sector.
   *
   * \param[in] sector Logical sector to be read.
   * \param[out] dst Pointer to the location that will receive the data.
   * \return true for success or false for failure.
   */
  virtual bool readSector(uint32_t sector, uint8_t* dst) = 0;

  /**
   * Read multiple sectors.
   *
   * \param[in] sector Logical sector to be read.
   * \param[in] ns Number of sectors to be read.
   * \param[out] dst Pointer to the location that will receive the data.
   * \return true for success or false for failure.
   */
  virtual bool readSectors(uint32_t sector, uint8_t* dst, size_t ns) = 0;

  /**
   * Read multiple sectors with callback as each sector's data
   *
   * \param[in] sector Logical sector to be read.
   * \param[in] ns Number of sectors to be read.
   * \param[out] dst Pointer to the location that will receive the data.
   * \param[in] callback Function to be called with each sector's data
   * \param[in] context Pointer to be passed to the callback function
   * \return true for success or false for failure.
   */
  virtual bool readSectorsCallback(uint32_t sector, uint8_t* dst, size_t ns,
   void (*callback)(uint32_t sector, uint8_t *buf, void *context), void *context) {
     for (size_t i = 0; i < ns; i++) {
       if (!readSector(sector + i, dst)) return false;
       callback(sector + i, dst, context);
     }
     return true;
  }

Then I that if you then setup the destination address to the constraints of the destination adders & 3 == 0... then it will I believe try to DMA the data...
But again I have not tried this...
 
About 3 years ago, I made a FAT free FS called ZeroFS
https://github.com/WMXZ-EU/zeroFS
Not that I suggest you to use this, but it may be easier to digest what I did than analysing FatFs
In general
you only have to initialize SdDisk, and then you can basic read/write commands
 
KurtE said:
I would look at the BlockDeviceInterface or in current version FsBlockDeviceInterface and see if it works for you.
Click to expand...

Thanks for the info. With the latest TeensyDuino installation, the hardware/teensy/avr/libraries/SdFat folder does not have FsBlockDeviceInterface, but I see that the greiman/SdFat GitHub repo does. Does this mean I should update the TeensyDuino SdFat? Not clear about where the official Teensy 4.1 SdFat lives...
 
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