Documentation

// D1 Mini V3 - join Wi-Fi and print IP
// Install: Boards Manager URL http://arduino.esp8266.com/stable/package_esp8266com_index.json
// Select Board: "LOLIN(WEMOS) D1 R2 & mini"

#include <ESP8266WiFi.h>

const char* ssid = "YOUR_SSID";
const char* pass = "YOUR_PASSWORD";

void setup() {
  Serial.begin(115200);
  delay(500);
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) { delay(300); Serial.print("."); }
  Serial.println();
  Serial.print("IP: "); Serial.println(WiFi.localIP());
  Serial.print("RSSI: "); Serial.print(WiFi.RSSI()); Serial.println(" dBm");
}

void loop() { delay(5000); }

// D1 Mini V3 - read the single ADC channel on A0
// The on-board divider gives 0 - 3.2V input range, 10-bit (0 - 1023)

void setup() {
  Serial.begin(115200);
}

void loop() {
  int raw = analogRead(A0);
  float voltage = raw * 3.2 / 1023.0;
  Serial.print("Raw="); Serial.print(raw);
  Serial.print("  V="); Serial.println(voltage, 3);
  delay(200);
}

# D1 Mini V3 - join Wi-Fi and serve a hello-world page (MicroPython)
# Flash MicroPython for ESP8266 from micropython.org

import network, socket, time

SSID = "YOUR_SSID"
PASS = "YOUR_PASSWORD"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(SSID, PASS)
while not wlan.isconnected():
    time.sleep(0.3)
print("IP:", wlan.ifconfig()[0])

s = socket.socket()
s.bind(("0.0.0.0", 80))
s.listen(1)

PAGE = b"HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n<h1>Hello from D1 Mini</h1>"

while True:
    conn, addr = s.accept()
    conn.recv(1024)
    conn.send(PAGE)
    conn.close()