SD卡

介绍

使用 VEX V5 的 SD 卡，您可以将文件存储在插入主机 SD 卡插槽的可移动 SD 卡上，并随时访问这些文件。无论是保存传感器数据还是加载自定义图像，这些方法都能让您完全掌控文件操作。可移动 SD 卡还方便您在主机和计算机之间轻松传输数据。

V5 Brain 需要一张容量不超过 32GB 的 SD 卡，格式为 FAT32。容量大于 32GB 的 SD 卡默认使用 exFAT 格式，这与 V5 Brain 不兼容。请确保您的 SD 卡在使用前已正确格式化为 FAT32。

所有文件必须放置在SD卡的根文件夹中才能访问。

对于以下示例，构造的 Brain 包括对 SD 卡方法的访问，并且在本 API 文档中所有后续示例中引用这些方法时都将使用它。

以下是所有方法的列表：

操作 — 执行文件操作并显示 SD 卡中的图像。

• loadfile — Loads a file from the SD card into a bytearray.

• savefile — Saves a bytearray onto the SD card.

• appendfile — Appends a bytearray to an existing file.

• draw_image_from_file — Displays a Bitmap Image from the SD card.

获取器 — 返回 SD 卡和文件信息。

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

• size — Returns the size of a file in bytes.

• exists — Returns a Boolean indicating whether a file is found on the SD card.

For information on constructing a Brain to gain access to the sdcard methods, see Brain.

行动

loadfile

loadfile loads a file from the SD card into a bytearray.

Usage:
Brain.SDcard.loadfile(filename, buffer);

参数	描述
filename	要加载的文件名（字符串形式）。文件名必须包含文件扩展名。
buffer	一个用于加载文件内容的现有字节数组。如果现有字节数组大于目标数组，则会覆盖其内容。如果现有字节数组小于目标数组，则该方法可能无法加载所有数据。默认情况下，如果没有提供缓冲区，则会返回一个新的字节数组。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // 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");
  }
}

savefile

savefile saves a bytearray onto the SD card.

Usage:
Brain.SDcard.savefile(filename, buffer);

参数	描述
filename	要保存的文件名（字符串类型）。文件名必须包含文件扩展名。如果文件已存在，则会覆盖它；如果文件不存在，则会创建一个新文件。
buffer	要写入文件的字节数组。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // 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

appendfile appends a bytearray to an existing file, adding new data to the end of the file without altering the current contents.

Usage:
Brain.SDcard.appendfile(filename, buffer);

参数	描述
filename	要追加的文件名（字符串形式）。文件名必须包含文件扩展名。
buffer	包含要追加数据的字节数组。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // 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);
}

drawImageFromFile

drawImageFromFile displays a Bitmap Image (BMP) stored on the SD card.

.bmp files are limited to 5120 pixels and 6KB in size.

Note: The V5 Brain only supports displaying .bmp files. 8-bit RLE encoding is recommended to minimize file size.

Usage
Brain.Screen.drawImageFromFile(filename, x, y);

参数	描述
filename	图片的文件名。
x	屏幕上图像左上角的 x 坐标。
y	屏幕上图像左上角的 y 坐标。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // Draw a bmp file on the Brain's screen at coordinate 0, 0
  Brain.Screen.drawImageFromFile("test_image.bmp", 0, 0);
}

获取器

isInserted

isInserted returns a Boolean indicating whether an SD card is currently inserted into the Brain.

• true — The Brain has an SD card inserted.

• false — The Brain does not have an SD card inserted.

Usage:
Brain.SDcard.isInserted()

参数	描述
	此方法没有参数。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // 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

size returns the size of a file in bytes.

Usage:
Brain.SDcard.size(filename);

参数	描述
filename	文件名（字符串形式）。文件名必须包含文件扩展名。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // 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

exists returns a Boolean indicating whether a file is found on the SD card.

• true — The file is on the SD card.

• false — The file is not on the SD card.

Usage:
Brain.SDcard.exists(filename);

参数	描述
filename	文件名（字符串形式）。文件名必须包含文件扩展名。

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();
  // 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);
  }
}