How to create a webserver to read an SD card with our Ethernet PLC Arduino

Arduino webserver to read a SD card in Ethernet industrial PLC controller
January 9, 2019 by
How to create a webserver to read an SD card with our Ethernet PLC Arduino
Boot & Work Corp. S.L., Support Team


In this example, we can see how to create a webserver to read an SD card into the PLC through an Ethernet connection for industrial automation. We will show how to create a server that when there is a request through a browser, you will see the directories and the files of the SD card.

Follow this post to ensure a good connection of the SD Card on the Ethernet Programmable Logic Controller Arduino.

Arduino sd card  Arduino sd card   Arduino sd card     


Ethernet PLC industrial controller

   M-Duino Family Products

   ESP32 Family Products

ESP32 web server sd card
Arduino SD Library

  Arduino SD Library

ESP32 web server sd card   Arduino automation


Once all is connected correctly, the next step is to make the right configuration of the Ethernet port and create the server:

   Copyright (c) 2017 Boot&Work Corp., S.L. All rights reserved

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <>.

#include <SD.h> #include <Ethernet2.h> #define SD_SS_PIN 53 File root; // Enter a MAC address for your controller below. The MAC can be defined by yourself following the MAC standard structure rules. byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; EthernetServer server(80); ///////////////////////////////////////////////////////////////////////////////// void setup() { Serial.begin(115200L); // Init Ethernet and TCP server Serial.println("Starting Ethernet ..."); Ethernet.begin(mac); server.begin(); // Init SD card Serial.println("Starting SD card ..."); if (!SD.begin(SD_SS_PIN)) { Serial.println("initialization failed!"); return; } Serial.print("IP address: "); Serial.println(Ethernet.localIP()); } /////////////////////////////////////////////////////////////////////////////// void loop() { EthernetClient client = server.available(); if (client) { char lastC = 0; while (client.connected()) { if (client.available()) { char c =; if ((c == '\n') && (lastC == '\n')) { client.println("HTTP/1.1 200 OK"); client.println("Content-Type: text/plain"); client.println("Connection: close"); client.println(); client.println("SD card files:"); root ="/"); printDirectory(root, client); break; } if (c != '\r') { lastC = c; } } } delay(50); client.stop(); } } //////////////////////////////////////////////////////////////////////////////// void printDirectory(File dir, Stream &stream) { while (true) { File entry = dir.openNextFile(); if (!entry) { // no more files break; } stream.print(; if (entry.isDirectory()) { stream.println("/"); } else { // files have sizes, directories do not stream.print(" ["); stream.print(entry.size(), DEC); stream.println("]"); } entry.close(); } }

See also

Basics: SD card in Arduino PLC


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How to create a webserver to read an SD card with our Ethernet PLC Arduino
Boot & Work Corp. S.L., Support Team January 9, 2019
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