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矩形波をパソコンのラインから出力

　パソコンから20Hzの矩形波をライン出力してみました。LEDが8個並んでいるのはいずれシリアルパラレル変換するためです。今回は並列に接続しているので同じように動作します。下記のコードは4CH出力していますが、動画のLEDのボードに接続しているのはデバイス0のLeftです。

#include <iostream>
#include <string>
#include <windows.h>
#include <MMSystem.h>

#pragma comment (lib, "winmm.lib")

int main() {

    WAVEFORMATEX wfe;
    static HWAVEOUT hWaveOut;
    static WAVEHDR whdr;
    static LPBYTE lpWave;
    WAVEFORMATEX wfe2;
    static HWAVEOUT hWaveOut2;
    static WAVEHDR whdr2;
    static LPBYTE lpWave2;
    int i, len, start, end;
    int frequency = 20;
    int terms = 10;
    int sampling = 192000;

    wfe.wFormatTag = WAVE_FORMAT_PCM;
    wfe.nChannels = 2;
    wfe.wBitsPerSample = 8;
    wfe.nBlockAlign = wfe.nChannels * wfe.wBitsPerSample / 8;
    wfe.nSamplesPerSec = sampling;
    wfe.nAvgBytesPerSec = wfe.nSamplesPerSec * wfe.nBlockAlign;
    waveOutOpen(&hWaveOut, 0, &wfe, 0, 0, CALLBACK_NULL);
    lpWave = (LPBYTE)calloc(wfe.nAvgBytesPerSec, terms * wfe.nChannels);

    wfe2.wFormatTag = WAVE_FORMAT_PCM;
    wfe2.nChannels = 2;
    wfe2.wBitsPerSample = 8;
    wfe2.nBlockAlign = wfe2.nChannels * wfe2.wBitsPerSample / 8;
    wfe2.nSamplesPerSec = sampling;
    wfe2.nAvgBytesPerSec = wfe2.nSamplesPerSec * wfe2.nBlockAlign;
    waveOutOpen(&hWaveOut2, 2, &wfe2, 0, 0, CALLBACK_NULL);
    lpWave2 = (LPBYTE)calloc(wfe2.nAvgBytesPerSec, terms * wfe2.nChannels);

    // 立ち上がりは出力を0にする
    for (i = 0; i < sampling * terms * wfe.nChannels; i++) {
        lpWave[i] = 128;
        lpWave2[i] = 128;
    }

    len = sampling / frequency; 

    // 最初の8サイクルは出力しない
    start = len * 8 * wfe.nChannels;
    start = 0;
    // 8サイクル波形を出力する
    end = start + len * 32 * wfe.nChannels;
    printf("start=%d, end=%d\n", start, end);

    for (i = start; i < end; i++) {
        if ((i % 2) == 0) {
            if ((i/2) % len < len / 2) { lpWave[i] = 228; }
            else { lpWave[i] = 28; }}}

    len /= 2;
    for (i = start; i < end; i++) {
        if ((i % 2) == 1) {
            if ((i / 2) % len < len / 2) { lpWave[i] = 228; }
            else { lpWave[i] = 28; }}}

    len *= 2;
    for (i = start; i < end; i++) {
        if ((i % 2) == 1) {
            if ((i / 2) % len < len / 2) { lpWave2[i] = 228; }
            else { lpWave2[i] = 28; }
        }
    }

    len /= 2;
    for (i = start; i < end; i++) {
        if ((i % 2) == 0) {
            if ((i / 2) % len < len / 2) { lpWave2[i] = 228; }
            else { lpWave2[i] = 28; }
        }
    }

    whdr.lpData = (LPSTR)lpWave;
    whdr.dwBufferLength = wfe.nAvgBytesPerSec * terms;
    whdr.dwFlags = WHDR_BEGINLOOP | WHDR_ENDLOOP;
    whdr.dwLoops = 1;
    waveOutPrepareHeader(hWaveOut, &whdr, sizeof(WAVEHDR));
    waveOutWrite(hWaveOut, &whdr, sizeof(WAVEHDR));

    whdr2.lpData = (LPSTR)lpWave2;
    whdr2.dwBufferLength = wfe.nAvgBytesPerSec * terms;
    whdr2.dwFlags = WHDR_BEGINLOOP | WHDR_ENDLOOP;
    whdr2.dwLoops = 1;
    waveOutPrepareHeader(hWaveOut2, &whdr2, sizeof(WAVEHDR));
    waveOutWrite(hWaveOut2, &whdr2, sizeof(WAVEHDR));

    char str[128];
    std::cout << "hello, world\n";
    std::cin >> str;

 

デバイス0の出力