How to Control LEDs with the tinyCore

Ready to light things up? Let’s start with the classic “Hello World”¹ of electronics: Blink!

We’ll start by learning how to flash the built-in LEDs, dim the lights with PWM², and then move up to controlling external ones!

Part 1: Blink the Onboard LEDs

Your tinyCore already has two built-in LEDs:

LED_BOOT (connected to GPIO21) - Usually indicates boot or error status
LED_SIG (connected to GPIO33) - General purpose signal LED

tinyCore Pinouts

Let’s start by them. No wiring required!

Basic Blink Program

Copy this code into your Arduino IDE:

Both LEDs on your tinyCore should now be flashing On and Off like the GIF above.

Alternating Blink Pattern

Let’s try something more interesting. Replace your loop() function with this alternating pattern:

Now the LEDs should be taking turns blinking!

Part 2: PWM Control (Dimming and Brightening)

The ESP32-S3 supports Pulse Width Modulation (PWM)³ for smooth brightness control. This will let us fade the LEDs in and out!

Smooth Breathing Effect

You should see your LEDs fading off and on smoothly, almost like two fireflies! (or do you call them lightning bugs??)

Manual Brightness Control

Another option is to manually set the LEDs to specific brightness levels:

Part 3: External LED with Breadboard

Now let’s add an external LED! The tinyCore has plenty of GPIO pins available for this.

You’ll need

Your tinyCore
A breadboard
A “Gumdrop” LED (any color)
A 220Ω resistor
Jumper wires (male-to-male)

??? question “Why do we need a resistor? Click for the Answer!”

Ohm’s Law states that the current through a device is inversely proportional to the resistance of that device. Put simply,a very ~~small~~ resistance equals a very LARGE current. LEDs have very little resistance, meaning we have to add a “current-limiting” resistor to protect them from getting fried!

We calculate the size of this resistor with a simple formula:

R = \frac{V_s - V_f}{I_f}

Where:

$R$ = Resistor value in Ohms
$V_s$ = Supply voltage (3.3V on the tinyCore)*
$V_f$ = LED forward voltage drop (typically 1.8-2.0V for red LEDs)
$I_f$ = Desired LED current (typically 10-20mA)

Example calculation for a red LED:

R = \frac{3.3V - 1.8V}{0.02A} = \frac{1.5V}{0.02A} = 75Ω

Lucky for us, 75 is a standard resistor value, but if it wasn’t, we’d round up to the next higher standard value, which is 100Ω. For extra margin of safety, 220Ω is commonly used and still provides good brightness while ensuring the LED won’t be damaged.

Available GPIO Pins:

Available GPIO

You can use any of the GPIO⁴: pins for your external LED (pictured in Yellow):

Digital pins: 8, 9, 10, 11, 12, 13
Analog pins: A0, A1, A2, A3, A4, A5

Wiring the External LED

Let’s use GPIO13:

LED short leg (cathode) → Pin 13
LED long leg (anode) → 220Ω resistor → GND Pin

External LED Wiring And here’s the circuit on a breadboard:

Code for External LED

Now it’s time to program the tinyCore to blink this LED! Here’s the code:

PWM Control for All Three LEDs

Let’s bring this whole thing home and control all three LEDs via PWM.

Understanding the Code

Digital Control

pinMode(pin, OUTPUT) - Sets a pin to output mode
digitalWrite(pin, HIGH) - Sends 3.3V to the pin (LED on)
digitalWrite(pin, LOW) - Sends 0V to the pin (LED off)

PWM Control

ledcAttach(channel, frequency, resolution) - Configures PWM settings
ledcWrite(channel, value) - Sets brightness (0-255 for 8-bit resolution)

Timer

delay(milliseconds) - Makes the program wait

Challenge Code

Spoilers Ahead!

SOS Signal

Troubleshooting

External LED not lighting?

Check polarity - long leg (+) goes to Pin 13, short leg (-, flat side) to resistor, resistor to Ground
Verify your resistor value (220Ω, should be Red, Red, Brown, Gold/Silver)
Make sure connections are secure on the breadboard
Could be burnt out, try another LED!

LED is very dim?

Check your resistor value - too high resistance dims the LED (For a brighter light, try 150Ω resistor instead)

Error: ‘ledcSetup’ was not declared in this scope

This usually happens with code generated by AI. LLM’s tend to hallucinate outdated syntax for the ESP32 board library. ledcSetup was removed in v3.0.7 of Expressif’s libraries and combined into ledcAttach. Make sure you use the latest syntax!

What’s Next?

Now that you can control LEDs, you can control almost anything: Motors, buzzers, relays - they all use similar digitalWrite() commands.

Ready to try:

In programming, “Hello World” refers to the simplest possible program that demonstrates basic functionality. New students will learn how to print the words “Hello World” in their specific programming language. ↩
PWM (Pulse Width Modulation) is a technique that rapidly turns power on and off to simulate different voltage levels. By changing how long the signal stays “on” versus “off,” we can make LEDs appear dimmer or brighter, even though they’re actually just blinking too fast for your eyes to see (thousands of times per second). ↩
Pulse Width Modulation is a technique that rapidly turns power on and off to simulate different voltage levels. By changing how long the signal stays “on” versus “off,” we can make LEDs appear dimmer or brighter, even though they’re actually just blinking too fast for your eyes to see (thousands of times per second). ↩
“GPIO” stands for General Purpose Input-Output. While labeled as “Digital” and “Analog”, all GPIO pins on the tinyCore can actually do both! (with some caveats). The labels simply indicate their primary intended use. ↩