说明: 这是学习笔记,仅做分享用途, 其中会引用其他博文的内容,时间关系不能一一将引用的文章都列举出来,如有冒犯,还请见谅

目录

参考资料

学习过程记录

SD卡引脚定义图

 硬件原理图

 实验代码

---

参考资料

乐鑫官方文档非常的详细以及清晰, 在使用之前可以优先浏览一遍官方文档:

SD/SDIO/MMC 驱动程序 - ESP32 - — ESP-IDF 编程指南 v4.4 文档 (espressif.com)

以下博文可以参考:

1. Arduino+ESP32 之 SD卡读写 - 一匹夫 - 博客园 (cnblogs.com)

2. 玩转 ESP32 + Arduino (二十四) SD卡读写_finedayforu的博客-CSDN博客

学习过程记录

首要前提当然是把开发编译环境搭建好(这个需要自行研究,有时间我再整理一下):

vscode+platformio框架

platform: Arduino

在学习过程中需要明确自己想要做什么, 此次目的是能够读写SD卡的数据.

背景知识:

ESP32有两种使用SD卡的方法，一种是使用SPI接口访问SD卡，另一种是使用SDMMC接口访问SD卡 。

SD卡引脚定义图

 硬件原理图

Arduino core for the ESP32中SPI方式占用4个IO口，SDMMC方式占用6个IO口,手上的这块板子设计好了SD卡的电路,需要清楚的是他使用的接线方式是怎样的:

ESP32引脚图

显然这里使用的是SPI的方式访问SD卡的,在后面的API使用的时候就要注意不要用到SDMMC的API了.

SD卡引脚图

 实验代码

 pio中提供了API以及sample code:

我们可以通过下面的位置查看SPI引脚是否和硬件是否一致,这有利于在出现问题的时候排查:

_spi_num这个变量的默认值为HSPI, _sck会被赋值为SCK, 和原理图中使用的引脚相同

 SD_Test中有非常详细的API方法,运行一下看看现象:

/*
 * Connect the SD card to the following pins:
 *
 * SD Card | ESP32
 *    D2       -
 *    D3       SS
 *    CMD      MOSI
 *    VSS      GND
 *    VDD      3.3V
 *    CLK      SCK
 *    VSS      GND
 *    D0       MISO
 *    D1       -
 */
#include "FS.h"
#include "SD.h"
#include "SPI.h"
 
void listDir(fs::FS &fs, const char * dirname, uint8_t levels){
    Serial.printf("Listing directory: %s\n", dirname);
 
    File root = fs.open(dirname);
    if(!root){
        Serial.println("Failed to open directory");
        return;
    }
    if(!root.isDirectory()){
        Serial.println("Not a directory");
        return;
    }
 
    File file = root.openNextFile();
    while(file){
        if(file.isDirectory()){
            Serial.print("  DIR : ");
            Serial.println(file.name());
            if(levels){
                listDir(fs, file.path(), levels -1);
            }
        } else {
            Serial.print("  FILE: ");
            Serial.print(file.name());
            Serial.print("  SIZE: ");
            Serial.println(file.size());
        }
        file = root.openNextFile();
    }
}
 
void createDir(fs::FS &fs, const char * path){
    Serial.printf("Creating Dir: %s\n", path);
    if(fs.mkdir(path)){
        Serial.println("Dir created");
    } else {
        Serial.println("mkdir failed");
    }
}
 
void removeDir(fs::FS &fs, const char * path){
    Serial.printf("Removing Dir: %s\n", path);
    if(fs.rmdir(path)){
        Serial.println("Dir removed");
    } else {
        Serial.println("rmdir failed");
    }
}
 
void readFile(fs::FS &fs, const char * path){
    Serial.printf("Reading file: %s\n", path);
 
    File file = fs.open(path);
    if(!file){
        Serial.println("Failed to open file for reading");
        return;
    }
 
    Serial.print("Read from file: ");
    while(file.available()){
        Serial.write(file.read());
    }
    file.close();
}
 
void writeFile(fs::FS &fs, const char * path, const char * message){
    Serial.printf("Writing file: %s\n", path);
 
    File file = fs.open(path, FILE_WRITE);
    if(!file){
        Serial.println("Failed to open file for writing");
        return;
    }
    if(file.print(message)){
        Serial.println("File written");
    } else {
        Serial.println("Write failed");
    }
    file.close();
}
 
void appendFile(fs::FS &fs, const char * path, const char * message){
    Serial.printf("Appending to file: %s\n", path);
 
    File file = fs.open(path, FILE_APPEND);
    if(!file){
        Serial.println("Failed to open file for appending");
        return;
    }
    if(file.print(message)){
        Serial.println("Message appended");
    } else {
        Serial.println("Append failed");
    }
    file.close();
}
 
void renameFile(fs::FS &fs, const char * path1, const char * path2){
    Serial.printf("Renaming file %s to %s\n", path1, path2);
    if (fs.rename(path1, path2)) {
        Serial.println("File renamed");
    } else {
        Serial.println("Rename failed");
    }
}
 
void deleteFile(fs::FS &fs, const char * path){
    Serial.printf("Deleting file: %s\n", path);
    if(fs.remove(path)){
        Serial.println("File deleted");
    } else {
        Serial.println("Delete failed");
    }
}
 
void testFileIO(fs::FS &fs, const char * path){
    File file = fs.open(path);
    static uint8_t buf[512];
    size_t len = 0;
    uint32_t start = millis();
    uint32_t end = start;
    if(file){
        len = file.size();
        size_t flen = len;
        start = millis();
        while(len){
            size_t toRead = len;
            if(toRead > 512){
                toRead = 512;
            }
            file.read(buf, toRead);
            len -= toRead;
        }
        end = millis() - start;
        Serial.printf("%u bytes read for %u ms\n", flen, end);
        file.close();
    } else {
        Serial.println("Failed to open file for reading");
    }
 
 
    file = fs.open(path, FILE_WRITE);
    if(!file){
        Serial.println("Failed to open file for writing");
        return;
    }
 
    size_t i;
    start = millis();
    for(i=0; i<2048; i++){
        file.write(buf, 512);
    }
    end = millis() - start;
    Serial.printf("%u bytes written for %u ms\n", 2048 * 512, end);
    file.close();
}
 
void setup(){
    Serial.begin(115200);
    if(!SD.begin()){
        Serial.println("Card Mount Failed");
        return;
    }
    uint8_t cardType = SD.cardType();
 
    if(cardType == CARD_NONE){
        Serial.println("No SD card attached");
        return;
    }
 
    Serial.print("SD Card Type: ");
    if(cardType == CARD_MMC){
        Serial.println("MMC");
    } else if(cardType == CARD_SD){
        Serial.println("SDSC");
    } else if(cardType == CARD_SDHC){
        Serial.println("SDHC");
    } else {
        Serial.println("UNKNOWN");
    }
 
    uint64_t cardSize = SD.cardSize() / (1024 * 1024);
    Serial.printf("SD Card Size: %lluMB\n", cardSize);
 
    listDir(SD, "/", 0);
    createDir(SD, "/mydir");
    listDir(SD, "/", 0);
    removeDir(SD, "/mydir");
    listDir(SD, "/", 2);
    writeFile(SD, "/hello.txt", "Hello ");
    appendFile(SD, "/hello.txt", "World!\n");
    readFile(SD, "/hello.txt");
    deleteFile(SD, "/foo.txt");
    renameFile(SD, "/hello.txt", "/foo.txt");
    readFile(SD, "/foo.txt");
    testFileIO(SD, "/test.txt");
    Serial.printf("Total space: %lluMB\n", SD.totalBytes() / (1024 * 1024));
    Serial.printf("Used space: %lluMB\n", SD.usedBytes() / (1024 * 1024));
}
 
void loop(){
 
}

列出了SD下所有文件目录,并且创建了对应的文件: