Summary of Arduino Sketch SoftBlink2
This article presents the SoftBlink2 Arduino sketch, which smoothly fades the onboard LED on pin 13 on and off using software PWM techniques. The sketch defines a PWM period and uses a function, LED_ramp(), to gradually vary the LED's brightness over specified durations. Different ramp speeds and brightness levels are demonstrated in the main loop through multiple calls to LED_ramp(). The program emphasizes modularity and improved coding practices over its predecessor, SoftBlink1, by condensing repeated code into a reusable function.
Parts used in the SoftBlink2 Arduino Sketch:
- Arduino board with built-in LED (typically on pin 13)
This sketch is used by Exercise: Soft Blink.
Full Source Code
The full code is all in one file SoftBlink2.ino.
// SoftBlink2 - fades the onboard LED on and off.
//
// Copyright (c) 2016, Garth Zeglin. All rights reserved. Licensed under the
// terms of the BSD 3-clause license as included in LICENSE.
//
// This builds upon the SoftBlink1 example to demonstrate more programming
// technique. Please see SoftBlink1 for the basic commentary.
// ================================================================================
// Define the period of the PWM waveform in milliseconds.
const int PWMPERIOD = 10;
// ================================================================================
// Configure the hardware once after booting up. This runs once after pressing
// reset or powering up the board.
void setup()
{
// Initialize the LED on pin 13 for output.
pinMode(LED_BUILTIN, OUTPUT);
}
// ================================================================================
// Run one iteration of the main event loop. The Arduino system will call this
// function over and over forever.
void loop()
{
// Perform a pattern of brightness ramps, both up and down and with different duration.
// These use the LED_ramp() function defined below.
// basic ramp up and down, full brightness
LED_ramp( 1000, 0, 10 );
LED_ramp( 1000, 10, 0 );
// now in double-time
LED_ramp( 500, 0, 10 );
LED_ramp( 500, 10, 0 );
LED_ramp( 500, 0, 10 );
LED_ramp( 500, 10, 0 );
// now in triple-time, using the loop to avoid repetition
for (int i = 0; i < 4; i += 1) {
LED_ramp( 333, 0, 10 );
LED_ramp( 333, 10, 0 );
}
// back to a second, but dimmer
for (int i = 0; i < 2; i += 1) {
LED_ramp( 1000, 0, 4 );
LED_ramp( 1000, 4, 0 );
}
// keep off for a second
delay(1000);
// and repeat
}
// ================================================================================
// Define a function to perform a single brightness ramp according to the
// specified parameters. It will not return until the full ramp has been
// performed, i.e., it will delay for the full ramp duration. This condenses
// the redundant code found in SoftBlink1 into a modular software building
// block.
//
// duration - ramp duration in milliseconds
// start - initial pulse duration, in milliseconds, must be no greater than PWMPERIOD
// end - final pulse duration, in milliseconds, must be no greater than PWMPERIOD
//
// The basic logic of the loop is the same as in SoftBlink1.
void LED_ramp(int duration, int start, int end)
{
int num_steps = duration / PWMPERIOD;
for(int i = 0; i < num_steps; i = i + 1) {
int time_on = map(i, 0, num_steps, start, end);
int time_off = PWMPERIOD - time_on;
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on
delay(time_on); // wait the specified number of milliseconds
digitalWrite(LED_BUILTIN, LOW); // turn the LED off
delay(time_off); // wait the specified number of milliseconds
}
}
// ================================================================================Source: SoftBlink2 Arduino Sketch
