Arduino - LED logarithmic fade.

arduino/008_led_logarithmic_fade/008_led_logarithmic_fade.ino

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+/**
+ * Copyright (c) 2020, Łukasz Marcin Podkalicki <lpodkalicki@gmail.com>
+ * Arduino/005
+ * Example of LED logarithmic fade (LED connected with resistor in series to pin 11)
+ */
+
+#include <stdint.h>
+#include <math.h>
+
+/**
+ * The instance of this class can control single LED.
+ * - on, off, toggle (any digital pin)
+ * - brightness (only PWM pins; i.e. for Arduino Uno: 3, 5, 6, 9, 10, 11)
+ */
+class BasicLed {
+public:
+  BasicLed(uint8_t pin): pin_(pin) {
+    pinMode(pin, OUTPUT); 
+  }
+  /* Light the LED up */
+  void on(void) {
+    digitalWrite(pin_, HIGH);
+  }
+  /* Turn the LED off */
+  void off(void) {
+    digitalWrite(pin_, LOW);
+  }
+  /* Toogle LED on/off */
+  void toggle(void) {
+    digitalWrite(pin_, !digitalRead(pin_));
+  }
+  /* Set LED brightness from range <0, 255> */
+  void setBrightness(uint8_t value) {
+    analogWrite(pin_, value);
+  }
+private:
+  uint8_t pin_;
+}; /* End of class BasicLed */
+
+class LogarithmicFade {
+public:
+  LogarithmicFade(const BasicLed& led, uint16_t extra_delay_us = 3000) : 
+    led_(led), extra_delay_us_(extra_delay_us) {}
+  /* fade-in */
+  void in(void) {
+    for (int16_t i = 0; i < 255; ++i) {
+      led_.setBrightness(i);
+      sleep(i);
+    }  
+  }
+  /* fade-out */
+  void out(void) {
+    for (int16_t i = 255; i >= 0; --i) {
+      led_.setBrightness(i);
+      sleep(i);
+    }
+  }
+private:
+  BasicLed led_;
+  uint16_t extra_delay_us_;
+
+  void sleep(uint8_t i) {
+    delayMicroseconds((uint16_t)(log(1. / (i + 1)) + 5.) * 1000);
+    delayMicroseconds(extra_delay_us_);
+  }
+}; /* End of class LogarithmicFade */
+
+BasicLed led(11);
+LogarithmicFade fade(led);
+
+void setup() {
+  // do nothing
+}
+
+void loop() {
+    fade.in();
+    fade.out();
+}
+