Correzione di luminosita

[sketchbook_andrea] / basic / pwm / pwm_7_1_states_dither / pwm_7_1_states_dither.ino

diff --git a/basic/pwm/pwm_7_1_states_dither/pwm_7_1_states_dither.ino b/basic/pwm/pwm_7_1_states_dither/pwm_7_1_states_dither.ino
new file mode 100644 (file)
index 0000000..4febeeb
--- /dev/null
+++ b/basic/pwm/pwm_7_1_states_dither/pwm_7_1_states_dither.ino
@@ -0,0 +1,64 @@
+/*
+  Change brightness of LED linearly to Human eye
+  256 step brightness using 8 bit PWM of Arduino
+  with quite a bit of dithering hard coded.
+  
+  https://ledshield.wordpress.com/2012/11/13/led-brightness-to-your-eye-gamma-correction-no/
+  https://learn.adafruit.com/led-tricks-gamma-correction/the-quick-fix
+*/
+
+
+#include <avr/pgmspace.h>
+#define CIELPWM(a) (pgm_read_byte_near(CIEL8 + a)) // CIE Lightness lookup table function
+
+/*
+  5 bit CIE Lightness to 8 bit PWM conversion
+  https://ledshield.wordpress.com/2012/11/13/led-brightness-to-your-eye-gamma-correction-no/
+  L* = 116(Y/Yn)^1/3 - 16 , Y/Yn > 0.008856
+  L* = 903.3(Y/Yn), Y/Yn <= 0.008856
+*/
+
+const uint8_t CIEL8[] PROGMEM = {
+   0,0,0,1,1,1,2,1,1,2,1,2,2,2,3,2,
+   2,2,3,2,2,3,2,3,3,3,4,3,3,3,4,4,
+   4,5,4,5,4,5,5,6,5,5,6,5,6,6,7,6,
+   7,7,8,7,8,8,9,8,9,10,9,10,10,11,10,11,
+   11,12,11,12,13,12,13,13,14,14,15,15,15,16,16,17,
+   17,17,18,18,19,19,20,20,21,21,22,22,23,23,24,24,
+   25,25,26,26,27,28,28,29,29,30,31,31,32,32,33,34,
+   34,35,36,37,37,38,39,39,40,41,42,43,43,44,45,46,
+   47,47,48,49,50,51,52,53,54,54,55,56,57,58,59,60,
+   61,62,63,64,65,66,67,68,70,71,72,73,74,75,76,77,
+   79,80,81,82,83,85,86,87,88,90,91,92,94,95,96,98,
+   99,100,102,103,105,106,108,109,110,112,113,115,116,118,120,121,
+   123,124,126,128,129,131,132,134,136,138,139,141,143,145,146,148,
+   150,152,154,155,157,159,161,163,165,167,169,171,173,175,177,179,
+   181,183,185,187,189,191,193,196,198,200,202,204,207,209,211,214,
+   216,218,220,223,225,228,230,232,235,237,240,242,245,248,252,255
+};
+
+int brightness = 0;             // initial brightness of LED
+int fadeAmount = 1;
+int led1Pin = 9;
+
+unsigned long startTime = 0;    // timing variables
+const long interval = 4;        // pause between each interval (256)
+
+
+void setup()  {  
+  pinMode(led1Pin, OUTPUT);     // declare pin 9 to be an output:
+}
+
+void loop()  {
+  unsigned long currentTime = millis();
+  if (currentTime - startTime >= interval)
+  {
+    startTime += interval;                         // increment timing sequence
+    analogWrite(led1Pin, CIELPWM(brightness));     // set the brightness of pin 9:, 0-31, 5 bit steps of brightness
+    brightness += fadeAmount;                      // change the brightness for next time through the loop:
+    if (brightness == 0 || brightness == 255)       // reverse the direction of the fading at the ends of the fade:
+    {
+      fadeAmount = -fadeAmount ;
+    }
+  }
+}