2.1 Hello, LED!

Just as printing “Hello, world!” is the first step in learning to program, using a program to drive an LED is the traditional introduction to learning physical programming.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
ESP32 Starter Kit	320+	ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
ESP32 WROOM 32E	BUY
ESP32 Camera Extension	-
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
LED	BUY

Available Pins

Here is a list of available pins on the ESP32 board for this project.

Available Pins

IO13, IO12, IO14, IO27, IO26, IO25, IO33, IO32, IO15, IO2, IO0, IO4, IO5, IO18, IO19, IO21, IO22, IO23

Schematic

This circuit works on a simple principle, and the current direction is shown in the figure. The LED will light up after the 220ohm current limiting resistor when pin26 outputs high level. The LED will turn off when pin26 outputs low level.

Wiring

Upload Code

1. You can open the file 2.1_hello_led.ino under the path of esp32-starter-kit-main\c\codes\2.1_hello_led. Or copy this code to the Arduino IDE directly .

2. Then connect the ESP32 WROOM 32E to your computer using a Micro USB cable.

   • Always displaying “Unknown COMxx”?

   

3. Select the board (ESP32 Dev Module) and the appropriate port.

   

4. Now, click the Upload button to upload the code to the ESP32 board.

   

5. After the code is uploaded successfully, you will see the LED blinking.

How it works?

1. Declare an integer constant named ledPin and assigns it the value 26.

   const int ledPin = 26;  // The GPIO pin for the LED
   

2. Now, initialize the pin in the setup() function, where you need to initialize the pin to OUTPUT mode.

   void setup() {
       pinMode(ledPin, OUTPUT);
   }
   

   • void pinMode(uint8_t pin, uint8_t mode);: This function is used to define the GPIO operation mode for a specific pin.

     • pin defines the GPIO pin number.

     • mode sets operation mode.

     The following modes are supported for the basic input and output:

     • INPUT sets the GPIO as input without pullup or pulldown (high impedance).

     • OUTPUT sets the GPIO as output/read mode.

     • INPUT_PULLDOWN sets the GPIO as input with the internal pulldown.

     • INPUT_PULLUP sets the GPIO as input with the internal pullup.

3. The loop() function contains the main logic of the program and runs continuously. It alternates between setting the pin high and low, with one-second intervals between the changes.

   void loop() {
       digitalWrite(ledPin, HIGH);   // turn the LED on (HIGH is the voltage level)
       delay(1000);                       // wait for a second
       digitalWrite(ledPin, LOW);    // turn the LED off by making the voltage LOW
       delay(1000);                       // wait for a second
   }
   

   • void digitalWrite(uint8_t pin, uint8_t val);: This function sets the state of the selected GPIO to HIGH or LOW. This function is only used if the pinMode was configured as OUTPUT.

     • pin defines the GPIO pin number.

     • val set the output digital state to HIGH or LOW.