ex12.c

/*=========================================================================

GFX EXAMPLE CODE - #12
        "PSG sound"

Copyright (C) 2004  Rafael de Oliveira Jannone

This example's source code is Public Domain.

WARNING: The author makes no guarantees and holds no responsibility for 
any damage, injury or loss that may result from the use of this source 
code. USE IT AT YOUR OWN RISK.

Contact the author:
        by e-mail : rafael AT jannone DOT org
        homepage  : http://jannone.org/gfxlib
        ICQ UIN   : 10115284

=========================================================================*/

#include <stdio.h>
#include "gfx.h"

main() {
        // prepare for the lamest example ever :)
        // at least is very simple and self-explained

        printf("initializing psg\n");

        psg_init();

        printf("sound output\n");

        // psgT transforms a frequency (in Hertz) to a suitable period value for PSG

        psg_channels(chanAll, chanNone); // set all channels to tone generation

        // the following frequencies are based on the 440 Hz (central A tone) tunning
        psg_tone(0, psgT(130.8)); // produce a C tone on the first channel
        psg_tone(1, psgT(164.8)); // produce a E tone on the second channel
        psg_tone(2, psgT(195.9)); // produce a G tone on the third channel

        psg_envelope(envUH, psgT(10), chanAll); // set a raising volume envelope on all channels

        printf("press spacebar to stop\n");

        while (!get_trigger(0)) {}

        psg_envelope(envD, psgT(10), chanAll); // set a fading volume envelope on all channels
}

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