After learning some Arduino and building some demos I decided to give it a try to another Chips. And this one is the ESP8266, you can find it in eBay or alixpress searching for “wemos D1”

Basically this little guy has kind of the same capabilities of an Atmel chip with less Digital outputs(9) but comes with WiFi built it. So that means you can use it as a station (STA) or a soft access point. That enables to do a lot of stuff, for example deploying this with sensors and being able to read from another device connected with the same Wifi all of them. In turn, you could control the digital outputs, and turn on / off stuff that are connected to the D1.

This is just a small example built in 5 minutes. I just connected a led with a proper resistance to D4. I still do not understand well with pin 2 turns on D4 but that is important now since it’s just a small demo.

UPDATE: Now I understand. You need to use the constants to get the right pins. So using D4 will automatically point it to the right pin that is 2 :) But it’s just much simpler to use the constants unless you want to go all the time to the datasheet. After building this simple example I build a bigger one that can send a message from the web to a simple display and show some weather measurements. Will share it later on a new post if there is any interest about it. You can comment here if it would be interesting for you to read it.

/*
* Based on ESP8266 LLMNR responder sample
* Copyright (C) 2017 Stephen Warren 
*
* Based on:
* ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
* Version 1.1
* Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
* ESP8266 port (c) 2015 Ivan Grokhotkov (ivan@esp8266.com)

* Instructions:
* - Update WiFi SSID and password as necessary.
* - Flash the sketch to the ESP8266 board.
* - Point your browser to http://ip-you-get-in-serial-monitor-arduino/
*
*/

#include 
#include 
#include 
#include 

const char* ssid = "yourRouterSSID";
const char* password = "yourPassword";

ESP8266WebServer web_server(80);

void handle_http_not_found() {
  web_server.send(404, "text/plain", "Not Found");
}

void handle_http_root() {
  // NOTE: Including bootstrap here just to make fancy buttons
  String headers = "	";
  String html = "Server options:
";
  html += "<a class='btn btn-primary' href='4/1' target='frame'>D4 on</a>
";
  html += "<a class='btn btn-primary' href='4/0' target='frame'>D4 off</a>
";
  html += "";
  web_server.send(200, "text/html", headers + html);
}

void handle4off() {
digitalWrite(2, 0);
web_server.send(200, "text/html");
}
void handle4on() {
digitalWrite(2, 1);
web_server.send(200, "text/html");
}

void setup(void) {
Serial.begin(115200);
pinMode(2, OUTPUT);
digitalWrite(2, 0);

// Connect to WiFi network
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
Serial.println("");

// Wait for connection
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.print("Connected to ");
Serial.println(ssid);
Serial.print("IP address: ");
Serial.println(WiFi.localIP());

// Start LLMNR responder
LLMNR.begin("esp8266");
Serial.println("LLMNR responder started");
// Start HTTP server
web_server.onNotFound(handle_http_not_found);
web_server.on("/", handle_http_root);
web_server.on("/4/1", handle4on);
web_server.on("/4/0", handle4off);
web_server.begin();

Serial.println("HTTP server started");
}

void loop(void) {
web_server.handleClient();
}

So after uploading this little script to your Wemos and of course updating your SSID and password to your router it should act like a server. Notice that I’m using a hidden Iframe to keep things simple, since I see other examples that submit a Form to itself and analyze the arguments. That is cool maybe for a bigger applicaion, but for simple apps, is enough to just point to an URL and reply with a 200 Http status.