E02. Why ESP32: Architecture, Memory and When to Leave the Uno

What you will do

Before Wi-Fi and sensors, get to know the board on your bench. Sketch 1 asks the ESP32 for its chip name, its Flash size and how much memory is free. Sketch 2 prints the free memory every 2 seconds, so you can compare it with the Wi-Fi sketches later.

Why move beyond the Uno?

The Uno is great for controlling things on your bench. Many projects now also need to talk to a phone or the internet - this is often called the Internet of Things (IoT). The ESP32 adds Wi-Fi and Bluetooth, runs much faster and has far more memory. Everything you learned on the Uno still applies: setup(), loop(), pins and Serial.

Uno and ESP32 side by side

The sketches look the same. The board underneath is very different.

Two kinds of memory

Flash is where your sketch is stored. It keeps its contents when the power is off.

RAM is working memory: it holds your variables while the sketch runs, and it empties at power-off. Wi-Fi and Bluetooth use a lot of RAM. The free RAM is called free heap, and ESP.getFreeHeap() tells you how much is left.

Some boards add extra RAM called PSRAM. You will not need it in this course.

When is the Uno enough?

Stay on the Uno for 5 V parts, shields and simple projects on your bench. Choose an ESP32 when you need Wi-Fi, Bluetooth, more memory or more speed - and accept its 3.3 V pins and different pin numbers.

Board setting for every ESP32 lesson

Tools -> Board -> esp32 -> ESP32 Dev Module. Serial Monitor at 115200. If you have a C3, C6 or P4 board, pick its own entry in the Board menu instead.

Wiring and safe build sequence

1. USB data cable from PC to ESP32 DevKit
2. Select ESP32 Dev Module (or matching board) and the correct port
3. No external parts required

What this sketch is for: Upload, open Serial Monitor at 115200 and read the three answers. Press EN to see them again.

void setup() {                             // setup() runs once
  Serial.begin(115200);                    // start Serial at the ESP32 speed
  delay(500);                              // give the USB link time to start

  Serial.print("Chip model: ");            // a label
  Serial.println(ESP.getChipModel());      // ask the ESP32 for its chip name

  Serial.print("Flash size (bytes): ");    // a label
  Serial.println(ESP.getFlashChipSize());  // how much space there is for sketches

  Serial.print("Free memory (bytes): ");   // a label
  Serial.println(ESP.getFreeHeap());       // how much working memory (RAM) is free
}

void loop() {                              // nothing to repeat in this sketch
}

What this sketch is for: Print the free memory every 2 seconds. Write the number down - in ESP32 Lesson 08 you will see how much Wi-Fi uses.

void setup() {                         // runs once
  Serial.begin(115200);                // start Serial at the ESP32 speed
}

void loop() {                          // runs over and over
  Serial.print("Free memory: ");       // a label
  Serial.print(ESP.getFreeHeap());     // the free working memory (RAM)
  Serial.println(" bytes");            // the unit, then a new line
  delay(2000);                         // wait 2 seconds before the next line
}