MEGA+WiFi R3 ATmega2560+ESP8266, flash 32MB, USB-TTL CH340G, Micro-USB

Overview

The RobotDyn MEGA+WiFi R3 combines a full Arduino Mega 2560 (ATmega2560) with an ESP8266EX Wi-Fi module on a single Arduino Mega-form-factor board. The two microcontrollers can operate independently or communicate with each other via UART, configured through an 8-position DIP switch.

A single CH340G USB-TTL converter handles programming for both MCUs — no external programmer or FTDI cable needed.

Why Use This Board

For projects that need both Arduino’s I/O power (54 digital pins, 16 analog, 15 PWM) and Wi-Fi connectivity without stacking a shield. The ESP8266 has its own 32 Mb flash, enough for serving web interfaces or OTA firmware updates while the ATmega handles real-time control.

DIP Switch Configuration

The 8-position DIP switch routes USB to one of two targets, links the two MCUs together, or isolates everything. Use this table from the original RobotDyn documentation:

DIP 8 is reserved (unused).

Programming

ESP8266 Setup in Arduino IDE

To program the ESP8266 side, you first need the ESP8266 board package installed in Arduino IDE:

1. File → Preferences → Additional Boards Manager URLs, add:

   http://arduino.esp8266.com/stable/package_esp8266com_index.json

2. Tools → Board → Boards Manager, search for esp8266 by ESP8266 Community, install (version 2.1.0 or later works)
3. Tools → Board → Generic ESP8266 Module
4. Tools → Upload Speed → 115200

Upload to ATmega2560

1. Set DIP 3, 4 = ON; rest OFF
2. Tools → Board → Arduino Mega 2560
3. Select serial port and upload

Upload Firmware to ESP8266

1. Set DIP 5, 6, 7 = ON; rest OFF (puts ESP in flash mode)
2. Press the Mode button on the board when starting upload (some board revisions)
3. Upload from Arduino IDE
4. After upload, set DIP 7 = OFF to run normally

MCU-to-MCU Communication

Set DIP 1, 2 = ON (Mega ↔ ESP via Serial3). ATmega’s Serial3 (pins 14 TX / 15 RX) is hard-wired to the ESP8266’s UART. Use Serial3.print() and Serial3.read().

Example: ATmega2560 controls ESP8266 LED via Serial3

This sketch (from the original RobotDyn documentation) runs on the ATmega2560, sets up the ESP8266 as a TCP server, then turns the onboard LED on/off based on characters received over WiFi:

void setup() {
  Serial3.begin(115200);
  pinMode(13, OUTPUT);
  delay(500);
  Serial3.println("AT+CIPMUX=1");
  delay(2000);
  Serial3.println("AT+CIPSERVER=1,5000");
  delay(2000);
  Serial3.println("AT+CIPSTO=3600");
  delay(2000);
}

void loop() {
  while (Serial3.available()) {
    char Rdata;
    Rdata = Serial3.read();
    if (Rdata == 'A' || Rdata == 'a') {
      digitalWrite(13, HIGH);
      delay(50);
    } else if (Rdata == 'B' || Rdata == 'b') {
      digitalWrite(13, LOW);
      delay(10);
      digitalWrite(13, HIGH);
      delay(10);
      digitalWrite(13, LOW);
    } else {
      digitalWrite(13, LOW);
    }
  }
}

Set DIPs as listed above (Mega2560 ↔ ESP8266), upload to the Mega, then telnet to the board’s IP on port 5000 and send “A” or “B” to control the LED.

Common Uses

• IoT data loggers (ATmega reads sensors, ESP uploads to cloud)
• Smart home controllers with web UI on ESP, hardware control on ATmega
• Remote-controlled robotics with web dashboard
• MQTT bridges with rich GPIO

Where to Buy in 2026

Original RobotDyn production has ended. Identical clones are widely available — the design is open-source. Look for boards explicitly marked with CH340G and 32 Mb flash to match the original.

Documentation

• Full pinout PDF — coming soon
• DIP switch reference card — coming soon
• Sample sketch (Mega ↔ ESP8266 bridge) — coming soon