Kentaro Okuda / mbed_sd_card
GitHub hosted
Public

SD card library for mbed projects.


Download repository: zip

SD card device

SD card library for mbed projects.

Prerequisites

  • mbed OS 5

Installation

Add this library to a mbed project.

mbed add https://github.com/lonesometraveler/mbed_sd_card.git

mbed app json

Enable the storage feature and SD component in mbed_app.json. Here is an example for LPC1768. For more info on Storage, see the mbed official documentation.

"target_overrides": {
    "LPC1768": {
         "target.features_add": ["STORAGE"],
         "target.components_add": ["SD"],
    }
}

Usage

Initialization

Pass SPI pins to the constructor.

SD sd(MOSI, MISO, CLK, CS);

Mount

Call mount. This returns 0 for success and a negative number for failure. 

int result = sd.mount();

Write

write writes data to a new file. If already exists, it erases the old content. This function returns size of written data or a negative number in case of failure.

int result = sd.write(FILE_PATH, buffer, sizeof buffer[0], length);

Append

append appends data to an existing file. This function returns size of written data or a negative number in case of failure.

int result = sd.append(FILE_PATH, buffer, sizeof buffer[0], length);

Read

read reads data from a specified address. This function returns size of read data or a negative number in case of failure.

int result = sd.read(FILE_PATH, address, buffer, sizeof buffer[0], length);

Example

#include "mbed.h"
#include "SD.h"

SD sd(MBED_CONF_SD_SPI_MOSI, MBED_CONF_SD_SPI_MISO, MBED_CONF_SD_SPI_CLK, MBED_CONF_SD_SPI_CS);
const char* FILE_PATH = "/fs/text.txt";

int main() {

    sd.mount();

    char* text1 = "The world is in my head. ";
    char* text2 = "My body is in the world.";
    char buffer[64];

    int size = sd.write(FILE_PATH, text1, sizeof(char), strlen(text1));
    size > 0 
        ? printf("wrote %d chars\r\n", size)
        : printf("error\r\n");

    size = sd.read(FILE_PATH, 0, buffer, sizeof(char), 64);
    size > 0
        ? printf("read: %s\r\n", buffer)
        : printf("error\r\n");

    size = sd.append(FILE_PATH, text2, sizeof(char), strlen(text2));
    size > 0 
        ? printf("appended %d chars\r\n", size)
        : printf("error\r\n");

    size = sd.read(FILE_PATH, 0, buffer, sizeof(char), 64);
    size > 0
        ? printf("read: %s\r\n", buffer)
        : printf("error\r\n");
}