Tuesday, May 10, 2016

NodeMCU/ESP8266 read from separate file in Flash File System

This example show how NodeMCU/ESP8266 read separate file in Flash File System.

In order to upload extra files to NodeMCU/ESP8266, a tool "ESP8266FS" is needed:

ESP8266FS is a tool which integrates into the Arduino IDE. It adds a menu item to Tools menu for uploading the contents of sketch data directory into ESP8266 flash file system.
  • Download the tool: https://github.com/esp8266/arduino-esp8266fs-plugin/releases/download/0.2.0/ESP8266FS-0.2.0.zip.
  • In your Arduino sketchbook directory, create tools directory if it doesn't exist yet
  • Unpack the tool into tools directory (the path will look like <home_dir>/Arduino/tools/ESP8266FS/tool/esp8266fs.jar)
  • Restart Arduino IDE
  • Open a sketch (or create a new one and save it)
  • Go to sketch directory (choose Sketch > Show Sketch Folder)
  • Create a directory named data and any files you want in the file system there
  • Make sure you have selected a board, port, and closed Serial Monitor
  • Select Tools > ESP8266 Sketch Data Upload. This should start uploading the files into ESP8266 flash file system. When done, IDE status bar will display SPIFFS Image Uploaded message.
ref: https://esp8266.github.io/Arduino/versions/2.1.0/doc/filesystem.html

This video show how to:

Example to read text file, test.txt, from Flash File System:

//To read separate file in file system
#include "FS.h"

void prepareFile(){
  Serial.println("Prepare file system");
  File file = SPIFFS.open("/test.txt", "r");
  if (!file) {
    Serial.println("file open failed!");  
  } else{
    Serial.println("file open success:)");

    while (file.available()) {

void setup() {
  Serial.println("To read separate file in file system");

void loop() {
  // put your main code here, to run repeatedly:


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