FLASH read / write operation and flash upload file of esp8266

1、Flash Read and write operations
Esp8266 Of Flash by 4M, among 1M For storing programs , Some of the other spaces are used for the system ,3M Most of the space left in the can be used to store files .

#include <FS.h>
String file_name = "/Fle/note.txt"; // The location and name of the file being read , Put it in /Fle Under the folder 

void setup() {
    
  Serial.begin(9600);
  Serial.println("");

  Serial.println("SPIFFS format start");
  SPIFFS.format();    //  format SPIFFS
  Serial.println("SPIFFS format finish");

  if (SPIFFS.begin()) {
     //  start-up SPIFFS
    Serial.println("SPIFFS Started.");
  } else {
    
    Serial.println("SPIFFS Failed to Start.");
  }
  file_write(file_name, "1111");
  file_read(file_name);
  file_add(file_name, "2222");
  file_read(file_name);
}
void loop() {
    
}

// Write operations 
void file_write(String file_name, String content)
{
    
  /***************************************** Write the contents of the flash file *************************************************/
  File dataFile = SPIFFS.open(file_name, "w");//  establish File Object is used to SPIFFS Medium file object （ namely /notes.txt） Write information 
  dataFile.println(content);       //  towards dataFile Write string information 
  dataFile.close();                           //  Close the file after writing 
  Serial.print(" The contents of the flash file have been written :");
  Serial.println(content);
}
// Read operations 
void file_read(String file_name)
{
    
  // Confirm whether there is file_name file 
  File dataFile;
  if (SPIFFS.exists(file_name))
  {
    
    // establish File Object to be used from SPIFFS Read files from 
    dataFile = SPIFFS.open(file_name, "r");
    // Read the contents of the file and output the file information through the serial port monitor 
    Serial.println(" Read the contents of the file ：");
    for (int i = 0; i < dataFile.size(); i++)
    {
    
      Serial.print((char)dataFile.read());
    }
  }
  else
  {
    
    Serial.print(file_name);
    Serial.print(" NOT FOUND.");
  }
  // Close the file after reading it 
  dataFile.close();
}
// Additional operations 
void file_add(String file_name, String content)
{
    
  if (SPIFFS.exists(file_name))
  {
    
    File dataFile = SPIFFS.open(file_name, "a");//  establish File Object is used to SPIFFS Medium file object （ namely /notes.txt） Write information 
    dataFile.println(content); //  towards dataFile Add string information 
    dataFile.close();                           //  Close the file after completing the file operation 
    Serial.println(" Content has been added :");
    Serial.println(content);
  }
  else 
  {
    
    Serial.print(file_name);
    Serial.print(" NOT FOUND.");
  }
}

2、Flash Upload the file and read the display , To verify whether it is really uploaded
Here is to upload to Flash The task of , You need to download one based on esp8266 and Arduino Of Flash File upload plugin
Here is the installation Flash Specific steps of file upload plug-in ：

tools Folders should be created by yourself , Put it in tools Under folder ESP8266FS The folder is the unzipped folder . Remember to restart after setting Arduino IDE Software can take effect .
Now use this plug-in Flash Upload and verify the file ：
First, create a new one under the project folder data Folder , Put the file to be uploaded in data Under the folder . open Arduino IDE Then click Tools -----ESP8266 Sketch Data Upload, Click to see Esp8266 The blue light is flashing . After burning, the file has been saved in Esp8266 Of Flash In the .

Now use the following procedure to verify ：

#include <FS.h>
String file_name = "/note.txt"; // The location and name of the file being read , Put it in the root directory 

void setup() {
    
  Serial.begin(9600);
  Serial.println("");

  if (SPIFFS.begin()) {
     //  start-up SPIFFS
    Serial.println("SPIFFS Started.");
  } else {
    
    Serial.println("SPIFFS Failed to Start.");
  }
  file_read(file_name);
  file_add(file_name, "\n2222");
  file_read(file_name);
}
void loop() {
    
}


void file_write(String file_name, String content)
{
    
  /***************************************** Write the contents of the flash file *************************************************/
  File dataFile = SPIFFS.open(file_name, "w");//  establish File Object is used to SPIFFS Medium file object （ namely /notes.txt） Write information 
  dataFile.println(content);       //  towards dataFile Write string information 
  dataFile.close();                           //  Close the file after writing 
  Serial.print(" The contents of the flash file have been written :");
  Serial.println(content);
}
void file_read(String file_name)
{
    
  // Confirm whether there is file_name file 
  File dataFile;
  if (SPIFFS.exists(file_name))
  {
    
    // establish File Object to be used from SPIFFS Read files from 
    dataFile = SPIFFS.open(file_name, "r");
    // Read the contents of the file and output the file information through the serial port monitor 
    Serial.println(" Read the contents of the file ：");
    for (int i = 0; i < dataFile.size(); i++)
    {
    
      Serial.print((char)dataFile.read());
    }
  }
  else
  {
    
    Serial.print(file_name);
    Serial.print(" NOT FOUND.");
  }
  // Close the file after reading it 
  dataFile.close();
}
void file_add(String file_name, String content)
{
    
  if (SPIFFS.exists(file_name))
  {
    
    File dataFile = SPIFFS.open(file_name, "a");//  establish File Object is used to SPIFFS Medium file object （ namely /notes.txt） Write information 
    dataFile.println(content); //  towards dataFile Add string information 
    dataFile.close();                           //  Close the file after completing the file operation 
    Serial.println(" Content has been added :");
    Serial.println(content);
  }
  else 
  {
    
    Serial.print(file_name);
    Serial.print(" NOT FOUND.");
  }
}

The above procedure cannot be carried out SPIFFS.format() Format operation , Otherwise, the newly saved files will be cleared , And notice the place data The files under the folder are placed in esp8266 Of Flash Under the root directory of , So the file directory in the program should also use /note.txt. At the same time, we should also pay attention not to /note.txt Write files , Otherwise, it will also be covered 123456789 This information .
Running results ：

As can be seen from the above , except 123456789, There are two more in the back 2222, This is because the program will run again after the download , In order to make the serial port display data, I press the reset button once , So the program ran twice , Added twice 2222.