Edgi-Talk_SDCARD Example Project

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Introduction

This example project runs on the M33 core with RT-Thread RTOS, demonstrating SD card file operations. It allows users to quickly learn how to mount an SD card, write and read files, and operate files through the serial command line.

SD Card Overview

1. Overview

SD Card (Secure Digital Card) is a compact, portable non-volatile storage device widely used in embedded systems, cameras, smartphones, and data loggers. It consists of a controller + NAND Flash memory and communicates with the host through a standard interface.

Key features:

  • Small size: typically 32 × 24 × 2.1 mm (standard)

  • Non-volatile NAND Flash storage

  • Supports hot-plug and power-loss protection

2. SD Card Types

By size:

Type

Dimensions

Standard SD

32 × 24 mm

Mini SD

21.5 × 20 mm

Micro SD (TF)

15 × 11 mm, most common

By capacity:

Type

Capacity

SDSC

1 MB ~ 2 GB

SDHC

4 GB ~ 32 GB

SDXC

32 GB ~ 2 TB

SDUC

2 TB ~ 128 TB

By speed class:

  • Class 2/4/6/10: minimum write speed 2/4/6/10 MB/s

  • UHS-I/II/III: up to 312 MB/s

  • Video Speed Class V6/V10/V30/V60/V90: suitable for video recording

3. SD Card Interface

  1. SPI mode: uses SPI bus (MISO, MOSI, SCK, CS), simple but slower.

  2. SD mode (1-bit/4-bit): dedicated SD bus, faster data transfer.

  3. UHS mode: high-speed interface, used in cameras and high-performance embedded systems.

4. Working Principle

  1. Command/Data transfer: host sends commands (CMD), card responds (R1, R2, etc.), read/write blocks (512 bytes each).

  2. Controller management: handles bad blocks, ECC, logical-to-physical mapping.

  3. Data storage: stored in NAND Flash, supports multiple erasures (typical 100,000 cycles).

5. Performance

Parameter

Description

Capacity

1 GB ~ 128 TB

Block size

512 Byte

Interface speed

SPI/SD 1-bit/4-bit/UHS

Max transfer

25 MB/s (standard), 312 MB/s (UHS-III)

Voltage

3.3 V (some Micro SD support 1.8 V)

Temperature

-25 ℃ ~ 85 ℃

Endurance

10^4 ~ 10^5 write cycles

6. Applications

  • Consumer electronics: phones, tablets, cameras

  • Embedded systems: MCU/FPGA storage, logging, configuration

  • Industrial: data acquisition, controllers

  • Audio/Video: high-speed video recording

  • Automotive: dashcams, navigation storage

Software Description

  • Developed on Edgi-Talk platform.

  • Example features:

    • Mount and initialize SD card

    • Write file using echo command

    • Read file using cat command

    • Print results on serial terminal

  • Provides a clear example of RT-Thread filesystem and SD card interface usage.

Usage

Build and Download

  1. Open and compile the project.

  2. Connect board USB to PC via DAP.

  3. Flash the compiled firmware.

  4. Insert SD card into the board.

Running Result

  • After powering on, the system mounts the SD card and initializes the filesystem.

  • Use the serial terminal to perform file operations:

  1. Write test.txt:

echo "Hello RT-Thread SDCARD!" ./test.txt

  1. Read file content:

cat ./test.txt

  • Sample serial output:

 \ | /
- RT -     Thread Operating System
 / | \     5.0.2 build Sep  8 2025 11:02:30
 2006 - 2022 Copyright by RT-Thread team
found part[0], begin: 1048576, size: 29.739GB
Hello RT-Thread
This core is cortex-m33
Mount SD card success!

> echo "Hello RT-Thread SDCARD!" ./test.txt
> cat ./test.txt
Hello RT-Thread SDCARD!

  • echo writes strings to files, cat reads and displays file content.

Notes

  • Ensure the SD card is inserted and formatted with FAT filesystem (FAT16/FAT32).

  • To modify graphical configuration:

tools/device-configurator/device-configurator.exe
libs/TARGET_APP_KIT_PSE84_EVAL_EPC2/config/design.modus

  • Save changes and regenerate code.

  • If SD card fails to mount, check hardware connections and power supply.

Startup Sequence

+------------------+
|   Secure M33     |
|  (Secure Core)   |
+------------------+
          |
          v
+------------------+
|       M33        |
| (Non-Secure Core)|
+------------------+
          |
          v
+-------------------+
|       M55         |
| (Application Core)|
+-------------------+

⚠️ Follow this flashing order strictly.

  • If the example does not run, first compile and flash Edgi-Talk_M33_S_Template to ensure core initialization.

  • To enable M55, open:

RT-Thread Settings --> Hardware --> select SOC Multi Core Mode --> Enable CM55 Core