ESP32 S3 UNO - Switch
This ESP32 S3 Uno switch tutorial shows you how to connect an ON/OFF switch to the ESP32 S3 Uno form board and read it with Arduino code. An ON/OFF switch is also called a toggle switch. You will print its state to the Serial Monitor and catch the moment it flips from OFF to ON or back.
In this tutorial, you will:
- Wire an ON/OFF toggle switch to the ESP32 S3 Uno.
- Read the switch state (ON or OFF) with the ezButton library.
- Detect switch events, like OFF to ON and ON to OFF.
- Debounce the switch so you get clean, stable readings.
Hardware Preparation
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Overview of ON/OFF Switch
Knowing how a switch behaves helps you write the right code for it. Unlike a push button, an ON/OFF switch keeps its position after you let it go.
When you flip it, it moves from OFF to ON, or from ON to OFF, and it stays there. To go back to the first state, you flip it again. This makes it a good choice for things like a power or mode selector in your project.
Pinout
Most ON/OFF switches come in two kinds: a version with two pins and a version with three pins.
This guide uses the two-pin version. Its two pins are the same, so you can connect them either way round.
How It Works
There are two ways to connect an ON/OFF switch to the ESP32 S3 Uno. Each way gives a different reading on the input pin, as the table shows.
| pin 1 | pin 2 | ESP32 S3 Uno Input Pin's State | |
|---|---|---|---|
| 1 | GND | ESP32 S3 Uno Input Pin (with pull-up) | HIGH ⇒ OFF, LOW ⇒ ON |
| 2 | 3.3V | ESP32 S3 Uno Input Pin (with pull-down) | HIGH ⇒ ON, LOW ⇒ OFF |
You only need one of these two ways. This tutorial uses the first one: one pin goes to GND, and the other goes to an input pin with the internal pull-up resistor turned on.
※ NOTE THAT:
ESP32 S3 Uno pins work at 3.3V and are NOT 5V tolerant. If you use the second way, connect the switch to 3.3V, never to 5V.
ESP32 S3 Uno Pinout
The image below shows the pinout of the ESP32 S3 Uno form board. Use it to find the Uno header pins (D7, GND…) and their GPIO numbers when you wire the switch.
Wiring Diagram
The switch needs only two wires: one to pin D7 and one to GND. The image and table below show the connections.
This image is created using Fritzing. Click to enlarge image
| ON/OFF Switch Pin | ESP32 S3 Uno Pin |
|---|---|
| Pin 1 | D7 (GPIO14) |
| Pin 2 | GND |
For a strong and safe joint, solder the wires to the switch pins with a Soldering Iron. Then slide a piece of Heat Shrink Tube over each joint to cover it.
ESP32 S3 Uno Code - ON/OFF Switch
A switch has the same problem as a button: its metal contacts bounce for a few milliseconds when you flip it, so the board can see many fast ON/OFF changes. You can learn more at Why do buttons and ON/OFF switches need debouncing?. Writing debounce code by hand takes extra work, so this sketch uses the ezButton library. It handles debouncing for you and turns on the internal pull-up resistor of the pin.
※ NOTE THAT:
Most switch projects fall into one of two cases:
- Case 1: Do one thing while the switch is ON, and the opposite thing while it is OFF.
- Case 2: Do something only at the moment the switch changes, from OFF to ON or from ON to OFF.
The sketch below covers both cases. It prints a message when the switch changes position, and it prints the current state on every loop.
The switch is read on GPIO14, which is pin D7 on the Uno header. isPressed() becomes true when the switch goes from OFF to ON, and isReleased() becomes true when it goes back to OFF. Because the pull-up is on, getState() returns HIGH when the switch is OFF and LOW when it is ON.
Detailed Instructions
- New to the ESP32 S3 Uno? Follow ESP32 S3 Uno - Getting Started first.
- Wire it up as shown in the diagram above.
- Connect the board to your computer with a USB Type-C cable.
- Open Arduino IDE, choose the ESP32S3 Dev Module board and the correct COM port.
- Install the ezButton library. See the steps here.
- Copy the code above and paste it into Arduino IDE.
- Upload the code by clicking the Upload button.
- Open the Serial Monitor and set the baud rate to 9600.
- Flip the switch to ON and watch the output.
- Flip the switch to OFF and check the output again.
- Tip: If the state looks reversed, that is normal for the pull-up method: LOW means ON. You can change the text in the code to match how your switch is mounted.
Video Tutorial
Watch the video below to see this ESP32 S3 Uno project step by step.
FAQ
Do I need an external resistor for the switch on the ESP32 S3 Uno?
No. The ezButton library turns on the internal pull-up resistor of the input pin. You only need two wires: one to D7 (GPIO14) and one to GND.
Can I connect the switch to 5V on the ESP32 S3 Uno?
No. ESP32 S3 Uno pins work at 3.3V and are not 5V tolerant. If you wire the switch to a supply instead of GND, use the 3.3V pin, and set the input to pull-down mode.
Why do I write 14 in the code instead of 7?
The ESP32 S3 Uno uses GPIO numbers in code, not the Uno header labels. Header pin D7 is GPIO14 on this board, so the code uses ezButton toggleSwitch(14);. Check the pinout image for other pins.
Is this code different from the UNO R4 version?
Only the pin number changes. The UNO R4 version uses pin 7, and the ESP32 S3 Uno version uses GPIO14 for the same D7 header position. The ezButton library works on both boards.
What if my project needs more pins than the Uno headers give?
The ESP32 S3 Uno has two extra rows of holes with more GPIOs: GPIO15 and GPIO16 (I/O, PWM, analog), GPIO45 and GPIO35 to GPIO42 (I/O, PWM), and GPIO47/GPIO48 (output only, PWM). Solder pin headers to use them and write the GPIO number in code. For extra switches, GPIO35 to GPIO42 or GPIO15/GPIO16 are good choices. Do not use GPIO47/GPIO48, because they are output only. Also note two warnings: (1) GPIO47/GPIO48 may run at 1.8V instead of 3.3V on some modules (especially ones with "V" in the name, like R8V or R16V), so 3.3V devices can be damaged or act strangely; (2) GPIO0, GPIO3 (D6), GPIO45 and GPIO46 (D9) are boot strapping pins, and a wrong connection can stop the board from booting or uploading code. Use the other extra pins first.
Why does the Serial Monitor print the state so fast?
The sketch prints the state on every pass of loop(), with no delay. This is fine for testing. In a real project, act only on isPressed() and isReleased(), or print the state only when it changes.
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No COM port shows up in Arduino IDE | USB driver missing or board not in upload mode | Install the CP210x or CH340 driver, use a data USB cable, or hold BOOT while pressing RESET |
| State never changes | Loose wire or wrong pin | Check that one switch pin goes to D7 (GPIO14) and the other to GND |
| State is reversed (ON shows OFF) | Pull-up logic means LOW is ON | This is normal, or swap the text in the code |
| Many fast OFF/ON messages for one flip | Contact bounce | Keep setDebounceTime(50) or raise it to 100 |
| Compile error about ezButton.h | Library not installed | Install the ezButton library from the Library Manager |
| Serial Monitor shows strange characters | Wrong baud rate | Set the Serial Monitor to 9600 baud |
| Board resets or acts oddly | Switch wired to 5V | Use GND (or 3.3V with pull-down), never 5V |