ExponentMap
Generates an exponentially growing array based on provided number of steps and maximum value.
ExponentMap
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.
Resources
Features
- Configurable number of steps and max value.
- Automatic calculation of optimum number of steps.
How it works
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 |
API
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));
Basic example
#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));
}
...
}
License
The MIT License (MIT)
Copyright (c) 2016 Vasil Kalchev
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.