Published January 5, 2026 © MIT

Build Your Own SD Card Chip | Arduino compatible

Embedded SD storage: Solder XTSD chip to your PCB, interface with Arduino via SPI. Works like SD card, no drivers needed!

BeginnerFull instructions provided4 hours249

Build Your Own SD Card Chip | Arduino compatible

Things used in this project

Hardware components

Flash Memory Card, SD Card

Breadboard (generic)

Jumper wires (generic)

Arduino Nano R3

JLCPCB Customized PCB

Software apps and online services

Arduino IDE

CircuitMaker by Altium Circuit Maker

Hand tools and fabrication machines

Hot Plate, 800 W

Solder Paste, Rework

Soldering iron (generic)

Solder Wire, Lead Free

Story

Have you ever wanted to integrate permanent storage directly into your PCB designs without using bulky SD card slots? Meet the XTX XTSD04GLGEAG - a tiny SD card chip that works exactly like a standard SD card but can be soldered directly to your circuit board!

In this Instructable, I'll show you how to create a custom breakout board for this chip, interface it with Arduino using SPI, and build a user-friendly serial menu system to manage files. This project is perfect for embedded systems, data loggers, or any application where space is at a premium.

The best part? Once assembled, this chip works seamlessly with computers, 3D printers, and any device that reads standard SD cards - no drivers needed!

Supplies

Hardware Components:

XTX XTSD04GLGEAG SD card chip
Arduino board (Uno, Nano, or compatible)
Custom PCB (design files provided)
2.54mm SIL pin headers (2x5 pins)
Solder paste (type 4 recommended)
Soldering iron with fine tip
Hotplate or reflow oven
Breadboard and jumper wires
SD card reader (for initial testing)

Software Tools:

Arduino IDE (latest version)
SdFat library by Bill Greiman
Altium Develop (or your preferred PCB design tool)
Serial terminal program (like PuTTY or Arduino Serial Monitor)

Manufacturing Services:

JLCPCB or similar PCB fabrication service
(Optional) 3D printer for enclosure

Schematic and PCB Design

Start by designing the breakout board in your preferred PCB design software. I used Altium Develop for this project.

Design Considerations:

Create a schematic that duplicates the XTSD chip for top and bottom assembly
Connect all chip pins to SIL connectors for easy breadboard compatibility

Follow standard SD card layout for the edge connection if you want reader compatibility

Follow standard SD card layout for the edge connection if you want reader compatibility
Set PCB thickness to 0.6mm - this is crucial for fitting into standard SD card readers.
Use 0.2mm trace width for signal line
Add clear pin labeling for easy wiring reference

Manufacturing Preparation:

Generate Gerber files from your design
Choose a solder mask color (I went with JLCPCB's signature blue)
Select ENIG (Gold Nickel) surface finish for better solderability
Verify all design rules before submission

Pro Tip: You can access my complete design files through the GitHub repository linked at the end of this guide.

Circuit Assembly

Once your PCBs arrive, it's time for assembly. The XTSD chip has a QFN package, which requires careful soldering.

Soldering the XTSD Chip:

Apply solder paste to all chip pads using a stencil or careful manual application
Use tweezers to precisely place the chip on the pads
Heat the board using a hotplate or reflow oven until the solder melts and reflows
Allow the board to cool naturally - don't force cool it!

Microscopic Inspection:After soldering, use a microscope or magnifying glass to check for:

Bridging between pins
Proper solder fillets Chip alignment

Adding Connectors:

Insert SIL pin headers into a breadboard
Place the PCB on top, aligning the holes with the pins
Solder each pin using a fine-tip soldering iron
Use copper braid to clean up any excess solder

Safety Note: Work in a well-ventilated area and use ESD protection when handling the chip.

Wiring to Arduino

The XTSD chip uses standard SPI interface, making Arduino integration straightforward.

SPI Connection Diagram:

XTSD04GLGEAG → Arduino Pin─────────────────────────CS (Chip Select) → D10MOSI (Master Out) → D11MISO (Master In) → D12SCK (Clock) → D13VCC (Power) → 3.3VGND (Ground) → GND

Breadboard Setup:

Place the breakout board on your breadboard
Connect power lines first (3.3V and GND)
Connect the four SPI signals (CS, MOSI, MISO, SCK)
Double-check all connections before powering on

Important: The chip requires 3.3V power! Do not connect it to 5V as this will damage the chip.

Final Test and Results

Upload the Code:

Install the SdFat library via Arduino Library Manager
Open the provided Arduino sketch
Select your board and port
Upload the code to your Arduino

Serial Interface Test:

Open Serial Monitor at 9600 baud
You should see the main menu with 8 options

Test each function:

List files (should show any existing files)
Create a new text file
Write data to the file
Read back the data
Delete files (with confirmation)
View SD card information
Test each function:List files (should show any existing files)Create a new text fileWrite data to the fileRead back the dataDelete files (with confirmation)View SD card information

Cross-Platform Testing:

Remove the board from Arduino
Insert it into a computer's SD card reader
Verify the computer recognizes it as a standard SD card
Check that files created via Arduino are accessible
Try copying files from your computer to the chip

Code

Arduino Code

#include <SPI.h>
#include <SdFat.h>

SdFat sd;
SdFile file;

// SD card chip select pin
const uint8_t chipSelect = SS;

// Function declarations
bool initializeSDCard();
void printMenu();
void listFiles();
void createFile();
void writeToFile();
void readFile();
void deleteFile();
void getCardInfo();
String readSerialInput(char endChar = '\n');


void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // Wait for serial port to connect
  }
  
  Serial.println(F(""));
  Serial.println(F("        XTX XTSD04GLGEAG SD Card         "));
  Serial.println(F("           Interface System              "));
  Serial.println(F("       --* BY DIY GUY Chris *--          "));
  Serial.println(F(""));
  Serial.println();
  
  // Initialize SD card
  if (!initializeSDCard()) {
    Serial.println(F(""));
    Serial.println(F("           SD CARD UNAVAILABLE        "));
    Serial.println(F("          System cannot continue        "));
    Serial.println(F(""));
    Serial.println(F(" Please:"));
    Serial.println(F("   1. Check hardware connections"));
    Serial.println(F("   2. Restart the Arduino"));
    Serial.println(F("   3. Ensure SD card is formatted properly"));
    while(true) {
      // Hang here since SD card is essential
      delay(1000);
    }
  }
  
  Serial.println(F(""));
  Serial.println(F("           SD CARD READY FOR USE       "));
  Serial.println(F(""));
  Serial.println();
  printMenu();
}

void loop() {
  if (Serial.available()) {
    char command = Serial.read();
    
    switch (command) {
      case '1':
        Serial.println(F("\n You selected: List all files"));
        listFiles();
        break;
      case '2':
        Serial.println(F("\n You selected: Create a new file"));
        createFile();
        break;
      case '3':
        Serial.println(F("\n  You selected: Write to a file"));
        writeToFile();
        break;
      case '4':
        Serial.println(F("\n  You selected: Read from a file"));
        readFile();
        break;
      case '5':
        Serial.println(F("\n  You selected: Delete a file"));
        deleteFile();
        break;
      case '6':
        Serial.println(F("\n You selected: Show menu"));
        printMenu();
        break;
      case '7':
        Serial.println(F("\n You selected: Show SD card info"));
        getCardInfo();
        break;
      case '8':
        Serial.println(F("\n You selected: Format operations"));
        formatOperations();
        break;
      default:
        if (command != '\n' && command != '\r') {
          Serial.println(F("\n Invalid option! Please choose 1-8"));
          printMenu();
        }
        break;
    }
  }
}

bool initializeSDCard() {
  int retryCount = 0;
  const int maxRetries = 3;
  
  while (retryCount < maxRetries) {
    if (sd.begin(chipSelect, SPI_FULL_SPEED)) {
      return true; // Success
    }
    
    retryCount++;
    
    Serial.println(F(""));
    Serial.println(F("           INITIALIZATION FAILED       "));
    Serial.println(F(""));
    Serial.println(F(" Please check:"));
    Serial.println(F("   1.  SD card is properly inserted"));
    Serial.println(F("   2.  Chip select pin is correct"));
    Serial.println(F("   3.  Wiring is proper"));
    Serial.println(F("   4.  Power cycle the device"));
    Serial.println();
    
    if (retryCount < maxRetries) {
      Serial.print(F(" Attempt "));
      Serial.print(retryCount + 1);
      Serial.print(F(" of "));
      Serial.print(maxRetries);
      Serial.println(F(" - Retrying in 3 seconds..."));
      delay(3000);
    }
  }
  
  // If we get here, all retries failed
  Serial.println();
  Serial.print(F(" Would you like to retry connection? (y/n): "));
  
  String response = readSerialInput();
  response.toLowerCase();
  
  if (response == "y" || response == "yes") {
    Serial.println(F(" Retrying SD card initialization..."));
    Serial.println();
    return initializeSDCard(); // Recursive retry
  }
  
  return false;
}

String readSerialInput(char endChar) {
  String input = "";
  unsigned long startTime = millis();
  
  while (millis() - startTime < 30000) { // 30 second timeout
    if (Serial.available()) {
      char c = Serial.read();
      
      if (c == endChar) {
        break;
      }
      
      if (c == '\b' || c == 127) { // Handle backspace
        if (input.length() > 0) {
          input.remove(input.length() - 1);
          Serial.print(F("\b \b")); // Erase the character
        }
      } else if (c >= 32 && c <= 126) { // Printable characters
        input += c;
        Serial.print(c); // Echo the character
      }
    }
  }
  
  Serial.println(); // New line after input
  return input;
}

void printMenu()
{
  Serial.println(F(""));
  Serial.println(F("               MAIN MENU               "));
  Serial.println(F(""));
  Serial.println(F("  1   List all files                   "));
  Serial.println(F("  2   Create a new file                "));
  Serial.println(F("  3   Write to a file                  "));
  Serial.println(F("  4   Read from a file                 "));
  Serial.println(F("  5   Delete a file                    "));
  Serial.println(F("  6   Show this menu                   "));
  Serial.println(F("  7   Show SD card info                "));
  Serial.println(F("  8   Format operations                "));
  Serial.println(F(""));
  Serial.println(F("      Tip: Use backspace to edit       "));
  Serial.println(F(""));
  Serial.print(F(" Enter your choice (1-8): "));
}

void listFiles() {
  Serial.println(F("\n"));
  Serial.println(F("              FILE LISTING            "));
  Serial.println(F(""));
  Serial.println(F("Files Name: "));
  Serial.println(F(""));
  sd.ls(LS_R);
  Serial.println(F(""));
  Serial.println(F(" Listing completed!"));
  printMenu();
}

void createFile() {
  Serial.println(F("\n"));
  Serial.println(  F("             CREATE NEW FILE          "));
  Serial.println(  F(""));
  
  Serial.println(F(" Available files:"));
  Serial.println(F(""));
  sd.ls(LS_R);
  Serial.println(F(""));
  
  Serial.print(F(" Enter filename to create: "));
  String filename = readSerialInput();
  
  if (filename.length() == 0) {
    Serial.println(F(" Error: No filename provided!"));
    printMenu();
    return;
  }
  
  // Add .txt extension if not present
  if (!filename.endsWith(".txt")) {
    filename += ".txt";
  }
  
  if (sd.exists(filename.c_str())) {
    Serial.println(F(" Error: File already exists!"));
  } else {
    if (file.open(filename.c_str(), O_CREAT | O_WRITE)) {
      file.close();
      Serial.println(F(" File created successfully!"));
      Serial.print(F(" Created: "));
      Serial.println(filename);
    } else {
      Serial.println(F(" Error: Failed to create file!"));
    }
  }
  
  printMenu();
}

void writeToFile() {
  Serial.println(F("\n"));
  Serial.println(  F("               WRITE TO FILE           "));
  Serial.println(  F(""));
  
  Serial.println(F(" Available files:"));
  Serial.println(F(""));
  sd.ls(LS_R);
  Serial.println(F(""));
  
  Serial.print(F(" Enter filename to write to: "));
  String filename = readSerialInput();
  
  if (filename.length() == 0) {
    Serial.println(F(" Error: No filename provided!"));
    printMenu();
    return;
  }
  
  // Add .txt extension if not present
  if (!filename.endsWith(".txt")) {
    filename += ".txt";
  }
  
  if (!sd.exists(filename.c_str())) {
    Serial.println(F(" Error: File doesn't exist!"));
    printMenu();
    return;
  }
  
  Serial.println(F(" Enter text to write (type # on new line to finish):"));
  Serial.println(F(""));
  String text = readSerialInput('#');
  
  if (file.open(filename.c_str(), O_WRITE | O_APPEND)) {
    file.println(text);
    file.close();
    Serial.println(F(""));
    Serial.println(F(" Text written successfully!"));
    Serial.print(F(" Updated: "));
    Serial.println(filename);
  } else {
    Serial.println(F(" Error: Failed to open file for writing!"));
  }
  
  printMenu();
}

void readFile() {
  Serial.println(F("\n"));
  Serial.println(  F("              READ FROM FILE           "));
  Serial.println(  F(""));
  
  Serial.println(F(" Available files:"));
  Serial.println(F(""));
  sd.ls(LS_R);
  Serial.println(F(""));
  
  Serial.print(F(" Enter filename to read: "));
  String filename = readSerialInput();
  
  if (filename.length() == 0) {
    Serial.println(F(" Error: No filename provided!"));
    printMenu();
    return;
  }
  
  // Add .txt extension if not present
  if (!filename.endsWith(".txt")) {
    filename += ".txt";
  }
  
  if (!sd.exists(filename.c_str())) {
    Serial.println(F(" Error: File doesn't exist!"));
    printMenu();
    return;
  }
  
  Serial.println(F("\n"));
  Serial.println(  F("              FILE CONTENT             "));
  Serial.println(  F(""));
  
  if (file.open(filename.c_str(), O_READ)) {
    int data;
    int lineCount = 0;
    while ((data = file.read()) >= 0) {
      Serial.write(data);
      if (data == '\n') lineCount++;
    }
    file.close();
    Serial.println(F("\n"));
    Serial.println(F(" End of file reached"));
    Serial.print(F(" Lines read: "));
    Serial.println(lineCount);
  } else {
    Serial.println(F(" Error: Failed to open file for reading!"));
  }
  
  printMenu();
}

void deleteFile() {
  Serial.println(F("\n"));
  Serial.println(  F("               DELETE FILE              "));
  Serial.println(  F(""));
  
  Serial.println(F(" Available files:"));
  Serial.println(F(""));
  sd.ls(LS_R);
  Serial.println(F(""));
  
  Serial.print(F("  Enter filename to delete: "));
  String filename = readSerialInput();
  
  if (filename.length() == 0) {
    Serial.println(F(" Error: No filename provided!"));
    printMenu();
    return;
  }
  
  // Add .txt extension if not present
  if (!filename.endsWith(".txt")) {
    filename += ".txt";
  }
  
  if (!sd.exists(filename.c_str())) {
    Serial.println(F(" Error: File doesn't exist!"));
  } else {
    Serial.print(F(" Are you sure you want to delete '"));
    Serial.print(filename);
    Serial.print(F("'? (y/n): "));
    String confirmation = readSerialInput();
    
    if (confirmation == "y" || confirmation == "Y") {
      if (sd.remove(filename.c_str())) {
        Serial.println(F(" File deleted successfully!"));
      } else {
        Serial.println(F(" Error: Failed to delete file!"));
      }
    } else {
      Serial.println(F(" Deletion cancelled!"));
    }
  }
  
  printMenu();
}

void getCardInfo() {
  Serial.println(F("\n"));
  Serial.println(  F("             SD CARD INFO              "));
  Serial.println(  F(""));
  
  cid_t cid;
  if (sd.card()->readCID(&cid)) {
    Serial.println(F(" Card Identification Data:"));
    Serial.println(F(""));
    Serial.print(F(" Manufacturer ID: 0x"));
    Serial.println(cid.mid, HEX);
    Serial.print(F(" OEM ID: "));
    Serial.print(char(cid.oid[0]));
    Serial.println(char(cid.oid[1]));
    Serial.print(F(" Product: "));
    for (uint8_t i = 0; i < 5; i++) {
      Serial.print(char(cid.pnm[i]));
    }
    Serial.println();
    Serial.print(F(" Version: "));
    Serial.print(cid.prvN());
    Serial.print(F("."));
    Serial.println(cid.prvM());
    Serial.print(F(" Serial number: 0x"));
    Serial.println(cid.psn(), HEX);
    Serial.println(F(""));
  }
  
  uint32_t totalSectors = sd.card()->sectorCount();
  uint32_t freeClusters = sd.vol()->freeClusterCount();
  uint32_t sectorsPerCluster = sd.vol()->sectorsPerCluster();
  
  Serial.print(F(" Total capacity: "));
  Serial.print(totalSectors * 512E-9);
  Serial.println(F(" GB"));
  
  Serial.print(F(" Used space: "));
  Serial.print((totalSectors - (freeClusters * sectorsPerCluster)) * 512E-9);
  Serial.println(F(" GB"));
  
  Serial.print(F(" Free space: "));
  Serial.print(freeClusters * sectorsPerCluster * 512E-9);
  Serial.println(F(" GB"));
  
  Serial.print(F(" Usage: "));
  Serial.print(100.0 - ((freeClusters * sectorsPerCluster * 100.0) / totalSectors));
  Serial.println(F(" %"));
  
  Serial.println(F(" Card info retrieved successfully!"));
  printMenu();
}

void formatOperations() {
  Serial.println(F("\n"));
  Serial.println(  F("            FORMAT OPERATIONS          "));
  Serial.println(  F(""));
  
  Serial.println(F(" Warning: These operations modify the file system"));
  Serial.println(F(" Available format operations:"));
  Serial.println(F(""));
  Serial.println(F("1.  Show file system status"));
  Serial.println(F("2.    Quick format (delete all files)"));
  Serial.println(F("3.  Back to main menu"));
  Serial.println(F(""));
  Serial.print(F(" Enter your choice (1-3): "));
  
  String choice = readSerialInput();
  
  if (choice == "1") {
    showFileSystemStatus();
  } else if (choice == "2") {
    quickFormat();
  } else if (choice == "3") {
    Serial.println(F(" Returning to main menu..."));
    printMenu();
  } else {
    Serial.println(F(" Invalid choice!"));
    printMenu();
  }
}

void showFileSystemStatus() {
  Serial.println(F("\n"));
  Serial.println(F("           FILE SYSTEM STATUS          "));
  Serial.println(F(""));
  
  uint32_t clusterCount = sd.vol()->clusterCount();
  uint32_t freeClusters = sd.vol()->freeClusterCount();
  uint32_t usedClusters = clusterCount - freeClusters;
  
  Serial.print(F(" Total clusters: "));
  Serial.println(clusterCount);
  Serial.print(F(" Used clusters: "));
  Serial.println(usedClusters);
  Serial.print(F(" Free clusters: "));
  Serial.println(freeClusters);
  Serial.print(F(" Usage: "));
  Serial.print((usedClusters * 100.0) / clusterCount);
  Serial.println(F(" %"));
  
  Serial.println(F("\n Files on card:"));
  Serial.println(F(""));
  sd.ls(LS_R | LS_SIZE);
  Serial.println(F(""));
  
  printMenu();
}

void quickFormat() {
  Serial.print(F(" ARE YOU SURE? This will delete ALL files! (y/n): "));
  String confirmation = readSerialInput();
  
  if (confirmation == "y" || confirmation == "Y") {
    Serial.println(F(" Deleting all files..."));
    
    SdFile root;
    root.openRoot(sd.vol());
    
    SdFile file;
    char fileName[13];
    int deletedCount = 0;
    
    while (file.openNext(&root, O_READ)) {
      file.getName(fileName, sizeof(fileName));
      file.close();
      
      if (sd.remove(fileName)) {
        Serial.print(F(" Deleted: "));
        Serial.println(fileName);
        deletedCount++;
      }
    }
    
    root.close();
    Serial.println(F(""));
    Serial.print(F(" Format completed! Deleted "));
    Serial.print(deletedCount);
    Serial.println(F(" files."));
  } else {
    Serial.println(F(" Format cancelled!"));
  }
  
  printMenu();
}

Credits

DIY GUY Chris

57 projects • 360 followers

I'm having fun while making electronics projects, I am an electrical engineer in love with "Do It Yourself" tasks.

Build Your Own SD Card Chip | Arduino compatible

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Supplies

Schematic and PCB Design

Circuit Assembly

Wiring to Arduino

Final Test and Results

Schematics

GERBER Design files

Code

Arduino Code

Credits

DIY GUY Chris

Comments

Embed the widget on your own site

Build Your Own SD Card Chip | Arduino compatible

Build Your Own SD Card Chip | Arduino compatible

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Supplies

Schematic and PCB Design

Circuit Assembly

Wiring to Arduino

Final Test and Results

Schematics

GERBER Design files

Code

Arduino Code

Credits

DIY GUY Chris

Comments

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