MicroSD basics

The built-in microSD card slot on Inkplate 6 MOTION can be of great use for your project. It can store a very large number of quality image files to be displayed and read and write data between deep sleeps. This page contains basic examples which will help you quickly get started with using the built-in microSDs card slot.

8GB microSD card inserted in Inkplate 6 MOTION

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Inkplate 6 MOTION uses the SdFat library

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All supported card formats are: FAT16, FAT32, exFAT

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All supported card types are: SD, SDHC and SDXC

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Preparing the microSD card before usage

For best results, use the official SD card formatter to format the card to FAT32 before usage.

The official SD Card formatter

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Initializing

Before the microSD card can be used in code, it must first be initialized, this powers on the microSD card circuitry and does all the nescessary memory allocations. In this code snippet, the microSD card is initialized and the result of the initialization is checked:

// Inkplate must be initialized before this

// Let's init the microSD card
if (!inkplate.microSDCardInit())
{
    // Print error message if the card could not be initialized
    inkplate.print("Couldn't init microSD card!");
    inkplate.partialUpdate();
    // Go to infinite loop - stop code
    while (1)
        ;
}
inkplate.print("MicroSD init success!");
inkplate.partialUpdate();

inkplate.microSDCardInit()

Initializes the microSD card on the Inkplate 6MOTION. Powers up the card, configures the necessary pins, and attempts to initialize the card interface.

Returns: Returns true if the initialization was successful, otherwise returns false.

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Reading and writing

Place a sample example.txt file on the microSD card and write something in it, this code snippet will read it and print it to the e-Paper:

// Make sure the microSD card is initialized by this point

File file; // Create a SdFile object
// This will only open the file in read only mode:
file = inkplate.sdFat.open("example.txt", O_RDONLY);
if (!file)
{
    // Print error message if the file couldn't be opened back
    inkplate.print("Couldn't open the created file!");
    inkplate.partialUpdate();
    // Go to infinite loop
    while (1)
        ;
}
// File is opened
// Read file contents to buffer
char buffer[128];
int bytesRead = file.read(buffer, sizeof(buffer) - 1);

file.close(); // Close the file, important!

// Bytes have been read
if (bytesRead > 0)
{
    buffer[bytesRead] = '\0'; // Null-terminate the c-style string
    // Let's print it to Inkplate!
    inkplate.println("\nFile contents:\n");
    inkplate.println(buffer);
}
else
{
    // Print error message if the file couldn't be opened
    inkplate.print("Couldn't read the test string!");
}
// Update the display with the result of the sketch
inkplate.partialUpdate();

Writing to a writeFile.txt file on the microSD card is similar:

char * testString = "Hi Inkplate!"; 
// Let's create the .txt file and write to it
// This will create the file if it doesn't exist, and open it in read-write mode if it exists:
File file = inkplate.sdFat.open("writeFile.txt", O_CREAT | O_RDWR);
if (!file)
{
    // Print error message if the file couldn't be created
    inkplate.print("Couldn't create the file on SD card!");
    inkplate.partialUpdate();
    // Go to infinite loop
    while (1)
        ;
}
// Write to the file and close it
file.print(testString);
file.close();

Before diving into the function details, here is the full example which provides a great overview:

SD Text read and write example

A full example on how to initialize the microSD card, read and write data to it

inkplate.sdFat.open()

Open a file from the SD card, this is a function from the SdFat library.

Returns: Returns the SdFile object if it was successful, false if it failed

Function parameters:

Type	Name	Description
const char *	path	The path to the file which is being opened, if it's in the root folder just write the filename.
oflag_t	oflag	The settings for opening the file. The different flags have to be OR'd, eg. O_CREAT | O_RDWR. Below is a table of these flags and what they mean.

Flag	Hex Value	Description
O_RDONLY	0x00	Open for reading only.
O_WRONLY	0x01	Open for writing only.
O_RDWR	0x02	Open for reading and writing.
O_AT_END	0x04	Open at the end-of-file (EOF).
O_APPEND	0x08	Set append mode (writes are added to EOF).
O_CREAT	0x10	Create file if it does not exist.
O_TRUNC	0x20	Truncate file to zero length.
O_EXCL	0x40	Fail if the file already exists.
O_SYNC	0x80	Synchronized write I/O operations.

file.print()

Prints the given c-style string to the file at the current file pointer position.

Returns: Returns the number of characters successfully printed, or a negative value if an error occurs.

Function parameters:

Type	Name	Description
const char *	str	The c-style string to print to the file.

file.read()

Reads data from the file into the provided buffer. The function attempts to read up to a given number of bytes starting from the current file pointer.

Returns: Returns the number of bytes read, or -1 if an error occurs.

Function parameters:

Type	Name	Description
void *	buf	A pointer to the buffer where the read file data will be stored.
size_t	count	The maximum number of bytes to read from the file.

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In the above mentioned functions, the file pointer is like a marker where you continue reading the file from, so subsequent calls to file.print() and file.print() will continue from where you left off.

file.close()

Closes the file, ensuring that any buffered data is flushed to the storage medium and that all resources associated with the file are freed.

Returns: Returns true if the file was closed successfully, or false if an error occurred.

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Using this method, it's possible to write to a .csv file, making it easy to store a table or log of events!

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Full example

Inkplate_6_Motion_SD_Read_Write_Text.ino

Full example of reading and writing text to the microSD card.