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。

For the examples below, the constructed Brain includes access to the SD card methods and will be used in all subsequent examples throughout this API documentation when referring to those methods.

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.
filesize – Returns the size of a file in bytes.
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`	可选参数。用于加载文件内容的现有字节数组。如果现有字节数组较大，则会覆盖其内容。如果现有字节数组较小，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。

# Check for SD card and show a file's text
if brain.sdcard.is_inserted():
    # Save new text to a file
    brain.sdcard.savefile("Note.txt", bytearray("VEX"))
    # Load the file and print it
    data = brain.sdcard.loadfile("Note.txt")
    brain.screen.print(data.decode("utf-8"))
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`	可选参数。要写入文件的字节数组。

# Check for SD card and show a file's text
if brain.sdcard.is_inserted():
    # Save new text to a file
    brain.sdcard.savefile("Note.txt", bytearray("VEX"))
    # Load the file and print it
    data = brain.sdcard.loadfile("Note.txt")
    brain.screen.print(data.decode("utf-8"))
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。

# Add more text and display file size
if brain.sdcard.exists("Note.txt"):
    brain.sdcard.appendfile("Note.txt", bytearray("code"))
    size = brain.sdcard.size("Note.txt")
    brain.screen.print("Size: ")
    brain.screen.print(size)

draw_image_from_file #

draw_image_from_file 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.draw_image_from_file(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。

# Draw a bmp file on the Brain's screen at coordinate 0, 0
brain.screen.draw_image_from_file('test_image.bmp', 0, 0)

获取器 #

is_inserted #

is_inserted 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.is_inserted()

参数	描述
	此方法没有参数。

# Check for SD card and show a file's text
if brain.sdcard.is_inserted():
    # Save new text to a file
    brain.sdcard.savefile("Note.txt", bytearray("VEX"))
    # Load the file and print it
    data = brain.sdcard.loadfile("Note.txt")
    brain.screen.print(data.decode("utf-8"))
else:
    brain.screen.print("Insert SD card")

filesize #

filesize returns the size of a file in bytes.

Usage:
brain.sdcard.filesize(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。

# Add more text and display file size
if brain.sdcard.exists("Note.txt"):
    brain.sdcard.appendfile("Note.txt", bytearray("code"))
    size = brain.sdcard.filesize("Note.txt")
    brain.screen.print("Size: ")
    brain.screen.print(size)

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。

# Add more text and display file size
if brain.sdcard.exists("Note.txt"):
    brain.sdcard.appendfile("Note.txt", bytearray("code"))
    size = brain.sdcard.size("Note.txt")
    brain.screen.print("Size: ")
    brain.screen.print(size)

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。

# Add more text and display file size
if brain.sdcard.exists("Note.txt"):
    brain.sdcard.appendfile("Note.txt", bytearray(" World"))
    size = brain.sdcard.size("Note.txt")
    brain.screen.print("Size: ")
    brain.screen.print(size)