Examples

Fade an LED up and down

analogWrite walks D13's brightness up and back down forever.

Arduino Uno R30 libraries41 linesOverall confidence 100%

SourceRead onlybasics_fade.ino

/* Fade This example shows how to fade an LED on pin 9 using the analogWrite() function. The analogWrite() function uses PWM, so if you want to change the pin you're using, be sure to use another PWM capable pin. On most Arduino, the PWM pins are identified with a "~" sign, like ~3, ~5, ~6, ~9, ~10 and ~11. This example code is in the public domain. https://docs.arduino.cc/built-in-examples/basics/Fade/ */ int led = 9; // the PWM pin the LED is attached to int brightness = 0; // how bright the LED is int fadeAmount = 5; // how many points to fade the LED by // the setup routine runs once when you press reset: void setup() { // declare pin 9 to be an output: pinMode(led, OUTPUT); } // the loop routine runs over and over again forever: void loop() { // set the brightness of pin 9: analogWrite(led, brightness); // change the brightness for next time through the loop: brightness = brightness + fadeAmount; // reverse the direction of the fading at the ends of the fade: if (brightness <= 0 || brightness >= 255) { fadeAmount = -fadeAmount; } // wait for 30 milliseconds to see the dimming effect delay(30); }

What the parser saw

Extracted from #include · #define · pinMode · constructor arguments. The output of a deterministic parser, not an AI.

Parts

ledidentifier led

60%

Buses

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Libraries

No libraries — read from pin names and pinMode alone.

Pin contract

An immutable contract owned by the project. It survives level changes; on a target board only the physical pins are remapped.

Logical name	Pin	Direction	Signal	Declared as
led	D9	out	pwm	#define

This page passes no verification gate. Logic (simulator), electrical (ERC · DRC) and physical (your confirmation) verification each run separately inside a project.

Next step

Same sketch, from simulation to PCB

The code stays as it is. Run it on avr8js in the Playground; import it into a project and the 8-pass electrical verification, KiCad board generation and Gerber export follow.

Run in Playground Import into a project