// license:BSD-3-Clause // copyright-holders:Derrick Renaud, Couriersud #include "emu.h" #include "flt_rc.h" // device type definition const device_type FILTER_RC = &device_creator; //************************************************************************** // LIVE DEVICE //************************************************************************** //------------------------------------------------- // filter_rc_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, "filter_rc", __FILE__), device_sound_interface(mconfig, *this), m_stream(nullptr), m_k(0), m_memory(0), m_type(FLT_RC_LOWPASS), m_R1(1), m_R2(1), m_R3(1), m_C(0) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void filter_rc_device::device_start() { m_stream = stream_alloc(1, 1, machine().sample_rate()); recalc(); save_item(NAME(m_k)); save_item(NAME(m_memory)); save_item(NAME(m_type)); save_item(NAME(m_R1)); save_item(NAME(m_R2)); save_item(NAME(m_R3)); save_item(NAME(m_C)); } //------------------------------------------------- // 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::recalc() { double Req; switch (m_type) { case FLT_RC_LOWPASS: if (m_C == 0.0) { /* filter disabled */ m_k = 0x10000; return; } Req = (m_R1 * (m_R2 + m_R3)) / (m_R1 + m_R2 + m_R3); break; case FLT_RC_HIGHPASS: case FLT_RC_AC: if (m_C == 0.0) { /* filter disabled */ m_k = 0x0; m_memory = 0x0; return; } Req = m_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 * m_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(); m_type = type; m_R1 = R1; m_R2 = R2; m_R3 = R3; m_C = C; recalc(); } void filter_rc_device::static_set_rc(device_t &device, int type, double R1, double R2, double R3, double C) { downcast(device).m_type = type; downcast(device).m_R1 = R1; downcast(device).m_R2 = R2; downcast(device).m_R3 = R3; downcast(device).m_C = C; }