1.2 FAT Filesystem throughput using SDMMC Media

This application calculates throughput by Writing and Reading data into a SD-Card at High Speed using the MPLAB Harmony File System and the SDMMC driver.

Description

Application performs below filesystem operations and throughput calculations on SD-Card using both Aligned and Unaligned buffers

  • Opens a file named throughput.txt in the root directory of the SD card.
  • Writes 10 Megabytes of data to file in chunks of 64 Kilobytes.
  • Once the operation is completed it calculates the time taken and overall throughput for write in Megabytes/second and displays on the console.
  • Reads 10 Megabytes of data from file in chunks of 64 Kilobytes.
  • Once the operation is completed it calculates the time taken and overall throughput for reading in Megabytes/second and displays on the console.
  • Closes the file once read is completed.
  • Checks if the Above steps need to be repeated for Unaligned buffer. If already done then it Glows an LED reporting success and the console will have throughput information for both Aligned and Unaligned buffers.

File system layer uses:

  • SDMMC Driver to communicate to SD Card

Downloading and Building the Application

To clone or download this application from Github, go to the main page of this repository and then click Clone button to clone this repository or download as zip file. This content can also be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/fs/sdmmc_fat_throughput/firmware.

To build the application, refer to the following table and open the project using its IDE.

Project NameDescription
sam_9x75_curiosity.XMPLABX project for SAM9X75 Curiosity Development Board

Setting Up AT91Bootstrap loader

To load the application binary onto the target device, we need to use at91bootstrap loader. Refer to the at91bootstrap loader documentation for details on how to use it to bootstrap the application binaries.

Setting Up the Hardware

The following table shows the target hardware for the application projects.

Project NameDescription
sam_9x75_curiosity.XSAM9X75 Curiosity Development Board

Setting Up SAM9X75 Curiosity Development Board

Additional hardware required:
  • SD Card with FAT32 file system
    • The SD Card should have at least 10MB of free space for the demo to work
Setting up the board:
  • SDMMC slot used is SD BOOT (J14)
  • Connect the UART DEBUG J35 on board to the computer using a UART-FTDI cable (to enable debug com port)
  • Connect the USB port J2 on board to the computer using a micro USB cable (to power the board)

Running the Application

  1. Build the application using its IDE
  2. Open the Terminal application (Ex.:Tera term) on the computer.
  3. Connect to the (USB to Serial) COM port and configure the serial settings as follows:
    • Baud : 115200
    • Data : 8 Bits
    • Parity : None
    • Stop : 1 Bit
    • Flow Control : None
  4. The LED is turned ON if there was no error during the file operations
    Refer to the following table for LED name:
    BoardLED Name
    SAM9X75 Curiosity Development BoardRGB_LED (Green)
  5. Calculated throughput values for Aligned and Un-aligned buffers are displayed on console as below:
    Note: The Values showed in the below output may differ slightly when demo is run.

Additional Steps (Optional)

To increase the throughput for the Un-aligned buffers you can follow below steps

  • Launch MHC for the project
  • Increase the size for the internal aligned buffer used by Filesystem service with some value as shown below. This internal buffer will be used when application buffer is Un-aligned and placed in cacheable region.
    Note: Increasing the size of the aligned buffer will consume more RAM.
  • Regenerate the project
  • Once done repeat the steps mentioned in Running The Application and observe the change in throughput for Un-aligned buffer