#include <SdFat.h>

const uint8_t chipSelect = 53; // Chip select pin

// Use SdFs for modern library compatibility
SdFs sd; 

// A 512-byte buffer is required for block transfers.
uint8_t writeBuffer[512];
uint8_t readBuffer[512];
const uint32_t testBlock = 100; // The block address to read/write

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

  Serial.println("\nInitializing SD card...");

  if (!sd.begin(chipSelect, SPI_FULL_SPEED)) {
    Serial.println("SD card initialization failed or card not present.");
    sd.initErrorHalt(); 
  }
  Serial.println("SD card initialized.");

  // --- Write a block ---
  for (uint16_t i = 0; i < 512; i++) {
    writeBuffer[i] = i % 256; // Fill with repeating pattern 0-255
  }

  Serial.print("Writing block ");
  Serial.print(testBlock);
  Serial.println("...");

  // Start the write operation for a single block
  if (!sd.card()->writeStart(testBlock)) { 
    Serial.println("Write start failed.");
    sd.initErrorHalt();
  }
  // Write the data to the started block
  if (!sd.card()->writeData(writeBuffer)) {
    Serial.println("Write data failed.");
    sd.initErrorHalt();
  }
  // Stop the write operation
  if (!sd.card()->writeStop()) {
     Serial.println("Write stop failed.");
     sd.initErrorHalt();
  }
  
  Serial.println("Write block success.");

  // --- Read the block back ---
  Serial.print("Reading block ");
  Serial.print(testBlock);
  Serial.println("...");

  // Start the read operation for a single block
  if (!sd.card()->readStart(testBlock)) {
    Serial.println("Read start failed.");
    sd.initErrorHalt();
  }
  // Read the data from the started block
  if (!sd.card()->readData(readBuffer)) {
    Serial.println("Read data failed.");
    sd.initErrorHalt();
  }
  // Stop the read operation (this function might not exist in your version, but it's safe to try)
  // if (!sd.card()->readStop()) { 
  //   Serial.println("Read stop failed.");
  //   sd.initErrorHalt();
  // }
  
  Serial.println("Read block success.");
  // Serial.println(readBuffer);

  // --- Verify the data ---
  bool success = true;
  for (uint16_t i = 0; i < 512; i++) {
    Serial.println(readBuffer[i]);
    if (readBuffer[i] != writeBuffer[i]) {
      // ... (error printing code remains the same) ...
      success = false;
      break;
    }
  }

  if (success) {
    Serial.println("Data verification successful!");
  } else {
    Serial.println("Data verification failed.");
  }
}

void loop() {
  // Nothing to do in loop
}