New mapping function for ambient light sensor
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@ -1,4 +1,39 @@
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function lightlevelmapping()
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MINBRIGHTNESS = 1;
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MAXBRIGHTNESS = 10;
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LIGHTSENSOR_BOTTOM = 0;
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LIGHTSENSOR_TOP = 150;
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x = [LIGHTSENSOR_BOTTOM - 10:LIGHTSENSOR_TOP + 10];
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b = zeros(size(9));
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LIGHTSENSOR_ALPHA1 = 0.02;
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LIGHTSENSOR_ALPHA2 = 0.20;
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a = LIGHTSENSOR_ALPHA1 * LIGHTSENSOR_TOP / log(LIGHTSENSOR_ALPHA2 / ...
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LIGHTSENSOR_ALPHA1);
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b = LIGHTSENSOR_ALPHA1 / a;
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c = MINBRIGHTNESS - a;
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y = a * exp(b*x) + c;
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y_ = round(y);
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[x; y_]
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figure
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plot(x, y, x, y_);
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A = axis;
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A(1) = LIGHTSENSOR_BOTTOM - 2;
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A(2) = LIGHTSENSOR_TOP - 2;
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A(3) = MINBRIGHTNESS - 2;
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A(4) = MAXBRIGHTNESS + 2;
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axis(A);
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grid on
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return
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function lightlevelmapping_old()
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MINBRIGHTNESS = 0;
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MAXBRIGHTNESS = 10;
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@ -75,7 +75,12 @@ void SWversion(void);
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#define LIGHTSENSOR_BOTTOM 0
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// top of light sensor (ambient light values at or higher than this level will
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// be mapped to MAXBRIGHTNESS)
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#define LIGHTSENSOR_TOP 900
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#define LIGHTSENSOR_TOP 150
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// slope of mapping function at bottom
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#define LIGHTSENSOR_ALPHA1 0.02
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// slope of mapping function at top
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#define LIGHTSENSOR_ALPHA2 0.20
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// weight for exponential decaying averaging (actual weigth is 2 ^ LIGHTSENSOR_WEIGHT)
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#define LIGHTSENSOR_WEIGHT 4
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// base of exponential mapping (must be > 1)
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@ -87,7 +92,7 @@ void SWversion(void);
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// start MAXBRIGHTNESS at DAYLIGHTHOUR (7 am)
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#define DAYLIGHTHOUR 7
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// NIGHT Brightness setting 0 = off, N_PWM_STEPS - 1 = full
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#define MINBRIGHTNESS 2
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#define MINBRIGHTNESS 1
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// start MINBRIGHTNESS at NIGHTLIGHTHOUR (7 pm)
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#define NIGHTLIGHTHOUR 19
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@ -180,6 +185,9 @@ void setup()
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{
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int n;
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// a, b, c and e are needed to compute lookup table for ambient light sensor
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float a, b, c, e;
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// initialise the hardware
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// initialize the appropriate pins as outputs:
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pinMode(LEDClockPin, OUTPUT);
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@ -245,6 +253,12 @@ void setup()
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}
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// compute ambient light level to brightness level mapping
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a = LIGHTSENSOR_ALPHA1 * LIGHTSENSOR_TOP / log(LIGHTSENSOR_ALPHA2 /
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LIGHTSENSOR_ALPHA1);
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b = LIGHTSENSOR_ALPHA1 / a;
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c = MINBRIGHTNESS - a;
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e = 2.718281828459045297;
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for (n = 0; n < sizeof(ambient_light_to_brightness); n++)
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{
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if (n <= LIGHTSENSOR_BOTTOM)
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@ -254,18 +268,15 @@ void setup()
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else
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{
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ambient_light_to_brightness[n] =
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round( pow((double) LIGHTSENSOR_BASE, (
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(double) brightness_per_unit_light * ((double) n - (double)
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LIGHTSENSOR_BOTTOM) / (double) (1 << LIGHTSENSOR_SCALE))) / pow((double)
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LIGHTSENSOR_BASE, (double) (MAXBRIGHTNESS - (double) MINBRIGHTNESS)) *
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((double) MAXBRIGHTNESS - (double) MINBRIGHTNESS) + (double) MINBRIGHTNESS );
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/* Serial.print(n);
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Serial.print(": ");
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Serial.println(ambient_light_to_brightness[n], DEC); */
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round(((float) a) * pow(e, ((float) b) *
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((float) n)) + (float) c);
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if (ambient_light_to_brightness[n] < MINBRIGHTNESS)
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ambient_light_to_brightness[n] = MINBRIGHTNESS;
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if (ambient_light_to_brightness[n] > MAXBRIGHTNESS)
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ambient_light_to_brightness[n] = MAXBRIGHTNESS;
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}
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}
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// determine whether we are running on old or new hardware
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// old hardware tied the push buttons to ground using 4k7 resistors
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// and relied on the buttons to pull them high
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