How to Use Adafruit SDIO microSD Breakout: Examples, Pinouts, and Specs

The Adafruit SDIO microSD Breakout is a versatile and compact breakout board designed for interfacing microSD cards with microcontrollers and other digital devices using the SD Input/Output (SDIO) protocol. This breakout board is particularly useful for applications requiring high-speed data logging, multimedia storage, or extending the storage capabilities of a device.

• Data logging with high write/read speeds
• Storing configuration files for embedded systems
• Multimedia storage for audio and video playback
• IoT devices requiring additional storage
• Portable storage solutions for microcontroller projects

• Interface: SDIO (3.0 compatible)
• Voltage: 3.3V input
• Current: Depends on microSD card and usage
• Dimensions: 25mm x 28mm x 2.5mm

1. Power Supply: Connect the 3V3 pin to a 3.3V power source and the GND pin to the ground.
2. SDIO Interface: Connect the CLK, CMD, and DAT0 (mandatory) pins to the corresponding SDIO pins on your microcontroller. DAT1, DAT2, and DAT3 are optional for 4-bit data transfer mode.
3. Card Detect (CD): Optionally, connect the CD pin to a GPIO pin on your microcontroller to detect the presence of a microSD card.

• Ensure that the power supply is stable and clean to prevent data corruption.
• Use a level shifter if your microcontroller operates at a voltage higher than 3.3V.
• Format the microSD card to the appropriate file system that your microcontroller supports (e.g., FAT32).
• For high-speed data transfer, use a microSD card with a fast read/write speed.
• Always safely eject the microSD card from your computer before removing it to prevent data loss.

• MicroSD card not recognized: Check the connections and ensure that the card is inserted correctly. Also, verify that the microSD card is formatted properly.
• Data corruption: Ensure a stable power supply and avoid removing the microSD card while writing/reading data.
• Slow data transfer: Use a class 10 or higher microSD card for better speed.

• If the microSD card is not detected, try using another card to rule out a defective card.
• For data corruption issues, reformat the microSD card and check the power supply for fluctuations.
• For slow data transfer, ensure that the SDIO interface is configured correctly for the maximum supported bus width.

#include <SPI.h>
#include <SD.h>

// Pin configuration for the Adafruit SDIO microSD Breakout
const int chipSelect = 10; // Chip select pin for the SD card

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // Wait for serial port to connect.
  }

  Serial.print("Initializing SD card...");

  // Note: The following line is for compatibility with default SPI pins
  if (!SD.begin(chipSelect)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  // Rest of the setup code
}

void loop() {
  // Main code to read/write from/to the SD card
}

Note: This example assumes that the SD library is compatible with the Adafruit SDIO microSD Breakout and that the breakout board is wired to the SPI pins of the Arduino UNO. The chip select pin can be connected to any available digital pin, but pin 10 is commonly used for this purpose.