That is possible. I managed several years ago and have of course just been incorporating it quite a few projects.
It is just HTML from a webserver, but if you have not created a webserver before at all it is skipping some educational steps to do this.
By now though i wonder why there is a need for an ESP32 at all ? the Wifi capability is usually the feature that is the one that makes one choose an ESP.
A lot of that is comprised of core functions that may not even be used , but adding some functionality to the code will not make the size of the binary grow much at all.
have a look at this thread and
this one which i bookmarked myself.
i have an example for the ESP8266
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WiFiMulti.h>
#include <ESP8266mDNS.h>
#include <ESP8266WebServer.h>
#include <FS.h> // Include the SPIFFS library
ESP8266WiFiMulti wifiMulti; // Create an instance of the ESP8266WiFiMulti class, called 'wifiMulti'
ESP8266WebServer server(80); // Create a webserver object that listens for HTTP request on port 80
File fsUploadFile; // a File object to temporarily store the received file
String getContentType(String filename); // convert the file extension to the MIME type
bool handleFileRead(String path); // send the right file to the client (if it exists)
void handleFileUpload(); // upload a new file to the SPIFFS
void setup() {
Serial.begin(115200); // Start the Serial communication to send messages to the computer
delay(10);
Serial.println('\n');
wifiMulti.addAP("ssid_from_AP_1", "your_password_for_AP_1"); // add Wi-Fi networks you want to connect to
wifiMulti.addAP("ssid_from_AP_2", "your_password_for_AP_2");
wifiMulti.addAP("ssid_from_AP_3", "your_password_for_AP_3");
Serial.println("Connecting ...");
int i = 0;
while (wifiMulti.run() != WL_CONNECTED) { // Wait for the Wi-Fi to connect
delay(1000);
Serial.print(++i); Serial.print(' ');
}
Serial.println('\n');
Serial.print("Connected to ");
Serial.println(WiFi.SSID()); // Tell us what network we're connected to
Serial.print("IP address:\t");
Serial.println(WiFi.localIP()); // Send the IP address of the ESP8266 to the computer
if (!MDNS.begin("esp8266")) { // Start the mDNS responder for esp8266.local
Serial.println("Error setting up MDNS responder!");
}
Serial.println("mDNS responder started");
SPIFFS.begin(); // Start the SPI Flash Files System
server.on("/upload", HTTP_GET, []() { // if the client requests the upload page
if (!handleFileRead("/upload.html")) // send it if it exists
server.send(404, "text/plain", "404: Not Found"); // otherwise, respond with a 404 (Not Found) error
});
server.on("/upload", HTTP_POST, // if the client posts to the upload page
[]() {
server.send(200);
}, // Send status 200 (OK) to tell the client we are ready to receive
handleFileUpload // Receive and save the file
);
server.onNotFound([]() { // If the client requests any URI
if (!handleFileRead(server.uri())) // send it if it exists
server.send(404, "text/plain", "404: Not Found"); // otherwise, respond with a 404 (Not Found) error
});
server.begin(); // Actually start the server
Serial.println("HTTP server started");
}
void loop() {
server.handleClient();
}
String getContentType(String filename) { // convert the file extension to the MIME type
if (filename.endsWith(".html")) return "text/html";
else if (filename.endsWith(".css")) return "text/css";
else if (filename.endsWith(".js")) return "application/javascript";
else if (filename.endsWith(".ico")) return "image/x-icon";
else if (filename.endsWith(".gz")) return "application/x-gzip";
return "text/plain";
}
bool handleFileRead(String path) { // send the right file to the client (if it exists)
Serial.println("handleFileRead: " + path);
if (path.endsWith("/")) path += "index.html"; // If a folder is requested, send the index file
String contentType = getContentType(path); // Get the MIME type
String pathWithGz = path + ".gz";
if (SPIFFS.exists(pathWithGz) || SPIFFS.exists(path)) { // If the file exists, either as a compressed archive, or normal
if (SPIFFS.exists(pathWithGz)) // If there's a compressed version available
path += ".gz"; // Use the compressed verion
File file = SPIFFS.open(path, "r"); // Open the file
size_t sent = server.streamFile(file, contentType); // Send it to the client
file.close(); // Close the file again
Serial.println(String("\tSent file: ") + path);
return true;
}
Serial.println(String("\tFile Not Found: ") + path); // If the file doesn't exist, return false
return false;
}
void handleFileUpload() { // upload a new file to the SPIFFS
HTTPUpload& upload = server.upload();
if (upload.status == UPLOAD_FILE_START) {
String filename = upload.filename;
if (!filename.startsWith("/")) filename = "/" + filename;
Serial.print("handleFileUpload Name: "); Serial.println(filename);
fsUploadFile = SPIFFS.open(filename, "w"); // Open the file for writing in SPIFFS (create if it doesn't exist)
filename = String();
}
else if (upload.status == UPLOAD_FILE_WRITE) {
if (fsUploadFile)
fsUploadFile.write(upload.buf, upload.currentSize); // Write the received bytes to the file
}
else if (upload.status == UPLOAD_FILE_END) {
if (fsUploadFile) { // If the file was successfully created
fsUploadFile.close(); // Close the file again
Serial.print("handleFileUpload Size: "); Serial.println(upload.totalSize);
server.sendHeader("Location", "/success.html"); // Redirect the client to the success page
server.send(303);
}
else {
server.send(500, "text/plain", "500: couldn't create file");
}
}
}
The ESP32 uses slightly different libraries but the general gist and the HTML code are almost the same.
i have my own functions and methods, but they are actually not all that complex if you are used to working with the WebServer.h though they are slightly different for an SD card than a SPIFFS or LittleFS file due to the variation in their implementation.
Regardless, the way to proceed is to first set up a simple webserver and understand how it works.
