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#include "emu.h"
#include "flt_rc.h"
const flt_rc_config flt_rc_ac_default = {FLT_RC_AC, 10000, 0, 0, CAP_U(1)};
// device type definition
const device_type FILTER_RC = &device_creator<filter_rc_device>;
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// qsound_device - constructor
//-------------------------------------------------
filter_rc_device::filter_rc_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, FILTER_RC, "RC Filter", tag, owner, clock),
device_sound_interface(mconfig, *this),
m_stream(NULL),
m_k(0),
m_memory(0),
m_type(0)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void filter_rc_device::device_start()
{
const flt_rc_config *conf = (const flt_rc_config *)static_config();
m_stream = stream_alloc(1, 1, machine().sample_rate());
if (conf)
set_RC_info(conf->type, conf->R1, conf->R2, conf->R3, conf->C);
else
set_RC_info(FLT_RC_LOWPASS, 1, 1, 1, 0);
}
//-------------------------------------------------
// sound_stream_update - handle a stream update
//-------------------------------------------------
void filter_rc_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
stream_sample_t *src = inputs[0];
stream_sample_t *dst = outputs[0];
int memory = m_memory;
switch (m_type)
{
case FLT_RC_LOWPASS:
while (samples--)
{
memory += ((*src++ - memory) * m_k) / 0x10000;
*dst++ = memory;
}
break;
case FLT_RC_HIGHPASS:
case FLT_RC_AC:
while (samples--)
{
*dst++ = *src - memory;
memory += ((*src++ - memory) * m_k) / 0x10000;
}
break;
}
m_memory = memory;
}
void filter_rc_device::set_RC_info(int type, double R1, double R2, double R3, double C)
{
double Req;
m_type = type;
switch (m_type)
{
case FLT_RC_LOWPASS:
if (C == 0.0)
{
/* filter disabled */
m_k = 0x10000;
return;
}
Req = (R1 * (R2 + R3)) / (R1 + R2 + R3);
break;
case FLT_RC_HIGHPASS:
case FLT_RC_AC:
if (C == 0.0)
{
/* filter disabled */
m_k = 0x0;
m_memory = 0x0;
return;
}
Req = R1;
break;
default:
fatalerror("filter_rc_setRC: Wrong filter type %d\n", m_type);
}
/* Cut Frequency = 1/(2*Pi*Req*C) */
/* k = (1-(EXP(-TIMEDELTA/RC))) */
m_k = 0x10000 - 0x10000 * (exp(-1 / (Req * C) / machine().sample_rate()));
}
void filter_rc_device::filter_rc_set_RC(int type, double R1, double R2, double R3, double C)
{
m_stream->update();
set_RC_info(type, R1, R2, R3, C);
}
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