Generates an exponentially growing array based on provided number of steps and maximum value.
The generated array can be used to control a PWM output perceived by humans (brigthness, sound...). Changing the power of an output device exponentially counteracts the logarithmic nature of the human perception.
The equation for generating the array is taken from Diarmuid.
- Configurable number of steps and max value.
- Automatic calculation of optimum number of steps.
The first two plots demonstrate that a linearly changing output in time is perceived by a person logarithmically. And the second two plots demonstrate that an exponentially chaning output in time is perceived by a person linearly.
Example "exponent map":
| Step | Value |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 5 |
| 5 | 9 |
| 6 | 15 |
| 7 | 25 |
| 8 | 39 |
| 9 | 63 |
| 10 | 101 |
| 11 | 160 |
| 12 | 255 |
The library consists of a single class ExponentMap, which generates the array based on the parameters it was constructed with. The first parameter is the desired number of steps and the second is the maximum value. If the number of steps is not specified, the optimal number of steps will be calculated automatically.
ExponentMap<byte> exp1(12, 255);
ExponentMap<byte> exp2(255);To get the value for a given step use the function operator. Alternatively the method stepToValue(step) can be used.
analogWrite(led, exp1(4));
analogWrite(led, exp1.stepToValue(4));#include "ExponentMap.h"
...
const byte led_pin = 3;
const byte pwm_max_value = 255;
byte steps_count = 12
byte current_step = 0;
ExponentMap<byte> e(steps_count, pwm_max_value);
...
void loop() {
...
if (up_button == true) {
analogWrite(led_pin, e(++current_step));
}
if (down_button == true) {
analogWrite(led_pin, e(--current_step));
}
...
}The MIT License (MIT)
Copyright (c) 2016 Vasil Kalchev
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