Classes to produce a computed sound wave on the analog output.

Dependents:   SoundWaveGeneratorTest SoundWaveGeneratorTest

Committer:
osmeest
Date:
Tue Feb 08 21:39:55 2011 +0000
Revision:
1:6864fd480178
Parent:
0:ed89ef772e92
Fix the Sine & Triangle wave computations which were very bad !

Who changed what in which revision?

UserRevisionLine numberNew contents of line
osmeest 0:ed89ef772e92 1 #include "snd_wave_generator/SineWave.h"
osmeest 0:ed89ef772e92 2 #include <cmath>
osmeest 0:ed89ef772e92 3
osmeest 0:ed89ef772e92 4 namespace snd_wave_generator {
osmeest 0:ed89ef772e92 5
osmeest 0:ed89ef772e92 6 void SineWave::prepare(std::size_t sampleRate)
osmeest 0:ed89ef772e92 7 {
osmeest 0:ed89ef772e92 8 std::size_t cycleLength = sampleRate / this->frequency;
osmeest 0:ed89ef772e92 9 this->buffer.resize(cycleLength);
osmeest 0:ed89ef772e92 10
osmeest 0:ed89ef772e92 11 std::size_t middle = cycleLength / 2;
osmeest 1:6864fd480178 12 std::size_t quarter = middle / 2;
osmeest 0:ed89ef772e92 13
osmeest 1:6864fd480178 14 float delta = 6.28 / (float(sampleRate) / float(this->frequency));
osmeest 0:ed89ef772e92 15 for(std::size_t i = 0; i < quarter; ++i) {
osmeest 0:ed89ef772e92 16 float dt = delta * i;
osmeest 0:ed89ef772e92 17 float dv = std::sin(dt) / 2.0;
osmeest 0:ed89ef772e92 18 float posValue = 0.5 + dv;
osmeest 0:ed89ef772e92 19 float negValue = 0.5 - dv;
osmeest 0:ed89ef772e92 20 this->buffer.write(i, posValue);
osmeest 0:ed89ef772e92 21 this->buffer.write(middle - i, posValue);
osmeest 0:ed89ef772e92 22 this->buffer.write(middle + i, negValue);
osmeest 0:ed89ef772e92 23 this->buffer.write(cycleLength - i, negValue);
osmeest 0:ed89ef772e92 24 }
osmeest 0:ed89ef772e92 25
osmeest 1:6864fd480178 26 this->buffer.write(quarter, 1.0);
osmeest 0:ed89ef772e92 27 if (middle - quarter != quarter) {
osmeest 1:6864fd480178 28 this->buffer.write(middle - quarter, 1.0);
osmeest 0:ed89ef772e92 29 }
osmeest 1:6864fd480178 30 this->buffer.write(cycleLength - quarter, 0.0);
osmeest 0:ed89ef772e92 31 if (middle + quarter != cycleLength - quarter) {
osmeest 0:ed89ef772e92 32 this->buffer.write(middle + quarter, 0.0);
osmeest 0:ed89ef772e92 33 }
osmeest 0:ed89ef772e92 34 }
osmeest 0:ed89ef772e92 35
osmeest 0:ed89ef772e92 36 } // snd_wave_generator