//-------------------------------------------------------------------
//	sinewave.cpp
//
//	This program will play a pure sine wave tone for one second.
//
//	programmer: ALLAN CRUSE
//	written on: 19 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for write(), close() 
#include <math.h>	// for sin()
#include <sys/ioctl.h>	// for ioctl()
#include <sys/soundcard.h>

#define SAMPLE_RATE	8000
#define NUM_SAMPLES	SAMPLE_RATE
#define TWO_PI		(3.14159 * 2.0)

unsigned char	pulsecode[ NUM_SAMPLES ];

int main( int argc, char **argv )
{
	// generate the pulse-code modulation data
	double	frequency = 220.0;	// cycles-per-second
	double	angle = (TWO_PI / SAMPLE_RATE) * frequency; 
	int	amplitude = 64, silence = 128;
	for (int sample = 0; sample < NUM_SAMPLES; sample++)
		{
		double	x = angle * sample;
		double	y = sin( x ) * amplitude;
		pulsecode[ sample ] = silence + (int)y;	
		}	

	// open the audio device and set its playback parameters
	int	bits = 8, chns = 1, rate = SAMPLE_RATE;
	int	dev = open( "/dev/audio", O_WRONLY );
	if ( dev < 0 ) { perror( "/dev/audio" ); exit(1); }
	if (( ioctl( dev, SNDCTL_DSP_SETFMT, &bits ) < 0 )
		||( ioctl( dev, SNDCTL_DSP_CHANNELS, &chns ) < 0 )
		||( ioctl( dev, SNDCTL_DSP_SPEED, &rate ) < 0 ))
		{ perror( "audio format not supported\n" ); exit(1); }

	// now playback the sound
	int	morebytes = NUM_SAMPLES;
	unsigned char	*pcm = pulsecode;
	while ( morebytes > 0 )
		{
		int	nbytes = write( dev, pcm, morebytes );
		morebytes -= nbytes;
		pcm += nbytes;
		}
	close( dev );		// close the audio playback device
}