SDcard#

Introduction#

The sdcard class is derived from the brain base class and provides access to files stored on a removable SD card inserted into the V5 Brain.

Using the SD card, your robot can load data such as images, read and write files, and store information for later use or transfer to a computer.

Access#

Brain.SDcard

Notes#

  • The V5 Brain supports SD cards up to 32GB in size.

  • The SD card must be formatted as FAT32.

    • SD cards larger than 32GB are typically formatted as exFAT, which is not compatible with the V5 Brain.

  • All files must be placed in the root directory of the SD card to be accessible.

  • The SD card must be inserted into the Brain before file operations can be performed.

  • File names and paths are case-sensitive.

Example#

/* This constructor is required when using VS Code.
A Brain is generated automatically at the start of
VEXcode projects. */

// Create the V5 Brain
brain Brain = brain();


// Add more text and display file size
if (Brain.SDcard.exists("Text.txt")) {
  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
}

Member Functions#

The sdcard class includes the following member functions:

  • loadfile — Loads the contents of a file from the SD card into a user-provided memory buffer.

  • savefile — Saves data from a user-provided buffer to a file on the V5 Brain’s SD card.

  • appendfile — Appends data from a user-provided buffer to the end of an existing file on the V5 Brain’s SD card.

  • isInserted — Returns a Boolean indicating whether an SD card is inserted into the Brain.

  • size — Returns the size, in bytes, of a file stored on the V5 Brain’s SD card.

  • exists — Returns a Boolean indicating whether a file with the specified name exists on the V5 Brain’s SD card.

.bmp and .png files stored on the SD card can be displayed on the V5 Brain screen using drawImageFromFile, which is accessed through Brain.Screen.

Before calling any sdcard member functions, a brain instance must be created, as shown below:

// Create the V5 Brain
brain Brain = brain();

loadfile#

Loads the contents of a file from the SD card into a user-provided memory buffer.

Available Functions 
int32_t loadfile(
  const char* name,
  uint8_t* buffer,
  int32_t len );
Parameters

Parameter

Type

Description

name

const char*

The name of the file to load from the SD card. The file’s name must include the file extension.

buffer

uint8_t*

A pointer to a buffer where the file data will be stored.

len

int32_t

The maximum number of bytes to read from the file, typically set to the size of the buffer.
Return Values

Returns the number of bytes successfully read from the file:

  • A positive value indicates how many bytes were loaded into the buffer.

  • 0 indicates that no data was read.

Notes

  • If the file is larger than len, only the first len bytes are read.

  • The buffer must be large enough to hold the requested data.

  • This function reads raw bytes and does not append a null terminator.

Examples 
// Check for SD card and show a file's text
if (Brain.SDcard.isInserted()) {
  // Create a message to save to the SD card
  uint8_t message[] = "Hello from VEX!";

  // Save the message into "Text.txt"
  Brain.SDcard.savefile("Text.txt", message, sizeof(message));

  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
} else {
  Brain.Screen.print("Insert SD card");
}

aavefile#

Saves data from a user-provided buffer to a file on the V5 Brain’s SD card.

Available Functions 
int32_t savefile(
  const char* name,
  uint8_t* buffer,
  int32_t len );
Parameters

Parameter

Type

Description

name

const char*

The name of the file to save as a string. The file’s name must include the file extension.

buffer

uint8_t*

A pointer to a memory buffer containing the data to be written to the file.

len

int32_t

The number of bytes to write from the buffer to the file.
Return Values

Returns the number of bytes successfully written to the file:

  • A positive value indicates how many bytes were saved.

  • 0 indicates that no data was written.

Notes

  • If the file is larger than len, only the first len bytes are read.

  • If a file with the same name already exists, it will be overwritten.

  • This function does not allocate memory; the buffer must be created and managed by the user.

  • The function writes raw bytes and does not append a null terminator.

Examples 
// Check for SD card and show a file's text
if (Brain.SDcard.isInserted()) {
  // Create a message to save to the SD card
  uint8_t message[] = "Hello from VEX!";

  // Save the message into "Text.txt"
  Brain.SDcard.savefile("Text.txt", message, sizeof(message));

  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
} else {
  Brain.Screen.print("Insert SD card");
}

appendfile#

Appends data from a user-provided buffer to the end of an existing file on the V5 Brain’s SD card.

Available Functions 
int32_t appendfile(
  const char* name,
  uint8_t* buffer,
  int32_t len );
Parameters

Parameter

Type

Description

name

const char*

The name of the file to append data to on the SD card. The file’s name must include the file extension.

buffer

uint8_t*

A pointer to a memory buffer containing the data to be appended to the file.

len

int32_t

The number of bytes to append from the buffer to the file.
Return Values

Returns the number of bytes successfully appended to the file:

  • A positive value indicates how many bytes were appended.

  • 0 indicates that no data was appended.

Notes

  • If the file is larger than len, only the first len bytes are read.

  • The file must already exist on the SD card; this function does not create a new file.

  • This function does not allocate memory; the buffer must be created and managed by the user.

  • The function appends raw bytes and does not append a null terminator.

Examples 
// Create a message to save to a new file
uint8_t message[] = "Hello";

// Save only the characters, not the null terminator
Brain.SDcard.savefile("Message.txt", message, sizeof(message) - 1);

// Load the file
int fileSize = Brain.SDcard.size("Message.txt");
uint8_t buffer[fileSize + 1];
Brain.SDcard.loadfile("Message.txt", buffer, fileSize);

// Add null terminator so it can be printed safely
buffer[fileSize] = 0;
Brain.Screen.print("%s\n", buffer);

// Create more text to append to the same file
uint8_t moreText[] = " World!";

// Append only the characters, not the null terminator
Brain.SDcard.appendfile("Message.txt", moreText, sizeof(moreText) - 1);

// Load the updated file
fileSize = Brain.SDcard.size("Message.txt");
uint8_t buffer2[fileSize + 1];
Brain.SDcard.loadfile("Message.txt", buffer2, fileSize);

// Add null terminator
buffer2[fileSize] = 0;
Brain.Screen.newLine();
Brain.Screen.print("%s", buffer2);

isInserted#

Returns whether an SD card is currently inserted in the V5 Brain.

Available Functions 
bool isInserted();
Parameters

This function does not accept any parameters.

Return Values

Returns a Boolean indicating whether an SD card is inserted:

  • true — An SD card is inserted in the V5 Brain.

  • false — No SD card is inserted.

Notes

  • This function only checks for the presence of an SD card; it does not verify that the card is formatted or readable.

Examples 
// Check for SD card and show a file's text
if (Brain.SDcard.isInserted()) {
  // Create a message to save to the SD card
  uint8_t message[] = "Hello from VEX!";

  // Save the message into "Text.txt"
  Brain.SDcard.savefile("Text.txt", message, sizeof(message));

  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
} else {
  Brain.Screen.print("Insert SD card");
  }

size#

Returns the size, in bytes, of a file stored on the V5 Brain’s SD card.

Available Functions 
int32_t size(
  const char* name );
Parameters

Parameter

Type

Description

name

const char*

The name of the file on the SD card. The file’s name must include the file extension.
Return Values

Returns an int32_t representing the size of the file in bytes:

  • A positive value indicates the file size in bytes.

  • 0 indicates an empty file or that the file could not be found.

Notes

  • The returned size can be used to allocate a buffer before calling loadfile.

Examples 
// Check for SD card and show a file's text
if (Brain.SDcard.isInserted()) {
  // Create a message to save to the SD card
  uint8_t message[] = "Hello from VEX!";

  // Save the message into "Text.txt"
  Brain.SDcard.savefile("Text.txt", message, sizeof(message));

  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
} else {
  Brain.Screen.print("Insert SD card");
}

exists#

Returns whether a file with the specified name exists on the V5 Brain’s SD card.

Available Functions 
bool exists(
  const char* name );
Parameters

Parameter

Type

Description

name

const char*

The name of the file to check on the SD card. The file’s name must include the file extension.
Return Values

Returns a Boolean indicating whether the file exists:

  • true — A file with the specified name exists on the SD card.

  • false — No file with the specified name exists.

Examples 
// Add more text and display file size
if (Brain.SDcard.exists("Text.txt")) {
  // Get the size of the file
  int fileSize = Brain.SDcard.size("Text.txt");

  // Make a buffer to hold the file data
  uint8_t buffer[fileSize];

  // Load the file from the SD card into the buffer
  Brain.SDcard.loadfile("Text.txt", buffer, sizeof(buffer));

  // Display the file contents on the screen
  Brain.Screen.print("%s", buffer);
}
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