Файловая система, хранение файлов, добавление при компиляции непосредственно на флеш памяти программ

Простой пример добавления внешнего файла к программе при компиляции.

Обращение к данным в форме файла хранимого в основной памяти программ, запись

// Very basic Spiffs example, writing 10 strings to SPIFFS filesystem, and then read them back
// For SPIFFS doc see : https://github.com/esp8266/Arduino/blob/master/doc/filesystem.md
// Compiled in Arduino 1.6.7. Runs OK on Wemos D1 ESP8266 board.

#include "FS.h"

void setup() {
  Serial.begin(9600);
  Serial.println("\nVery basic Spiffs example, writing 10 lines to SPIFFS filesystem, and then read them back");
  SPIFFS.begin();
  // Next lines have to be done ONLY ONCE!!!!!When SPIFFS is formatted ONCE you can comment these lines out!!
  Serial.println("Please wait 30 secs for SPIFFS to be formatted");
  SPIFFS.format();
  Serial.println("Spiffs formatted");
}

void loop() {

  // open file for writing
  File f = SPIFFS.open("/f.txt", "w");
  if (!f) {
      Serial.println("file open failed");
  }
  Serial.println("====== Writing to SPIFFS file =========");
  // write 10 strings to file
  for (int i=1; i<=10; i++){
    f.print("Millis() : ");
    f.println(millis());
    Serial.println(millis());
  }

  f.close();

  // open file for reading
  f = SPIFFS.open("/f.txt", "r");
  if (!f) {
      Serial.println("file open failed");
  }  Serial.println("====== Reading from SPIFFS file =======");
  // write 10 strings to file
  for (int i=1; i<=10; i++){
    String s=f.readStringUntil('\n');
    Serial.print(i);
    Serial.print(":");
    Serial.println(s);
  }

  // wait a few seconds before doing it all over again

Еще пример

#include "FS.h"

void setup() {
  Serial.begin(115200);

  // always use this to "mount" the filesystem
  bool result = SPIFFS.begin();
  Serial.println("SPIFFS opened: " + result);

  // this opens the file "f.txt" in read-mode
  File f = SPIFFS.open("/f.txt", "r");
  
  if (!f) {
    Serial.println("File doesn't exist yet. Creating it");

    // open the file in write mode
    File f = SPIFFS.open("/f.txt", "w");
    if (!f) {
      Serial.println("file creation failed");
    }
    // now write two lines in key/value style with  end-of-line characters
    f.println("ssid=abc");
    f.println("password=123455secret");
  } else {
    // we could open the file
    while(f.available()) {
      //Lets read line by line from the file
      String line = f.readStringUntil('\n');
      Serial.println(line);
    }

  }
  file.close();
}

void loop() {
  // nothing to do for now, this is just a simple test

}