Serial Communication Between Arduino UNO and ESP32-CAM

This project is useful for:

1. ESP32-CAM control using Arduino
2. Sensor data transfer to ESP32
3. Camera-based IoT projects
4. Learning UART communication between 5V and 3.3V devices

How It Works

UART (Universal Asynchronous Receiver-Transmitter) allows two devices to communicate using TX (Transmit) and RX (Receive) lines.

1. Arduino UNO sends data via Serial TX
2. ESP32-CAM receives data via UART RX
3. Common GND is shared
4. ESP32-CAM uses Serial2 (GPIO16 & GPIO17)

⚠️ Important: ESP32-CAM works at 3.3V logic, so a voltage divider is recommended on Arduino TX → ESP32 RX.

Wiring Connections

To establish UART communication between the Arduino UNO and ESP32-CAM, follow the wiring steps below.

Connect Grounds (Important)

1. Connect GND of Arduino UNO to GND of ESP32-CAM
2. A common ground is required for proper serial communication

Serial Data Connection

1. Connect Arduino UNO TX (Pin 1) to ESP32-CAM RX (GPIO16)
2. This allows data to be transmitted from Arduino to ESP32-CAM

Voltage Level Protection (Recommended)

The Arduino UNO operates at 5V logic, while the ESP32-CAM uses 3.3V logic.

To protect the ESP32-CAM, use a voltage divider :

1. Place a 1.8kΩ resistor between Arduino TX and ESP32-CAM RX (GPIO16)
2. Place a 3.3kΩ resistor between ESP32-CAM RX (GPIO16) and GND

ESP32-CAM Programming Connections

1. Use a USB-to-TTL adapter to upload code
2. Connect U0R → TX, U0T → RX, 5V → 5V, GND → GND
3. Connect IO0 to GND while uploading the sketch

Arduino UNO Code (Sender)

void setup() {   

	 Serial.begin(9600);   

}   

void loop() {   

	 Serial.println("Hello from Arduino!");   

	 delay(1000);   

}   

📌 This code continuously sends text data from the Arduino to the ESP32-CAM every second.

ESP32-CAM Code (Receiver)

#include "HardwareSerial.h"   

HardwareSerial SerialESP32(2);   

void setup() {   

	 Serial.begin(115200);   

	 SerialESP32.begin(9600, SERIAL_8N1, 16, 17);   

	 Serial.println("ESP32-CAM Ready");   

}   

void loop() {   

	 if (SerialESP32.available()) {   

	   String data = SerialESP32.readStringUntil('\n');   

	   Serial.println("Received: " + data);   

	 }   

}   

📌 The ESP32-CAM reads data using Serial2 and prints it to the Serial Monitor.

How to Upload Code to ESP32-CAM

1. Connect IO0 to GND
2. Press RESET
3. Upload code using USB-to-TTL adapter
4. Disconnect IO0 from GND
5. Press RESET again

References

Original tutorial:

https://www.programmingboss.com/2023/01/serial-communication-between-arduino-and-esp32-CAM-UART-data-communication.html