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cmi01a: Add filters

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This commit is contained in:
Olivier Galibert 2024-10-06 19:43:53 +02:00
parent fc3a0daf84
commit f96914785f
2 changed files with 109 additions and 5 deletions
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99
src/mame/fairlight/cmi01a.cpp
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@ -135,6 +135,20 @@ void cmi01a_device::device_start()
save_item(NAME(m_rp));
save_item(NAME(m_ws));
save_item(NAME(m_dir));
save_item(NAME(m_ha0));
save_item(NAME(m_ha1));
save_item(NAME(m_hb0));
save_item(NAME(m_hb1));
save_item(NAME(m_hc0));
save_item(NAME(m_hc1));
save_item(NAME(m_ka0));
save_item(NAME(m_ka1));
save_item(NAME(m_ka2));
save_item(NAME(m_kb0));
save_item(NAME(m_kb1));
save_item(NAME(m_kb2));
}
void cmi01a_device::device_reset()
@ -175,10 +189,26 @@ void cmi01a_device::device_reset()
m_pitch = 0;
m_octave = 0;
m_ha0 = 0;
m_ha1 = 0;
m_hb0 = 0;
m_hb1 = 0;
m_hc0 = 0;
m_hc1 = 0;
m_ka0 = 1;
m_ka1 = 0;
m_ka2 = 0;
m_kb0 = 1;
m_kb1 = 0;
m_kb2 = 0;
m_bcas_q1_timer->adjust(attotime::from_hz(clock() / 2), 0, attotime::from_hz(clock() / 2));
m_zcint_pulse_timer->adjust(attotime::never);
m_rstb_pulse_timer->adjust(attotime::never);
m_sample_timer->adjust(attotime::never);
update_filters();
}
void cmi01a_device::sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs)
@ -189,15 +219,26 @@ void cmi01a_device::sound_stream_update(sound_stream &stream, std::vector<read_s
for (int sampindex = 0; sampindex < buf.samples(); sampindex++)
{
const s32 sample = (s32)(s8)(m_current_sample ^ 0x80);
const s32 env32 = (s32)m_env;
const s32 vol32 = (s32)m_vol_latch;
const s16 sample16 = (s16)(u16)((sample * env32 * vol32) >> 8);
buf.put_int(sampindex, sample16, 32768);
double sample = s8(m_current_sample ^ 0x80); // -128..127
double hbn = (sample + 2*m_ha0 + m_ha1 - m_ka1 * m_hb0 - m_ka2 * m_hb1) / m_ka0;
double hcn = (hbn + 2*m_hb0 + m_hb1 - m_kb1 * m_hc0 - m_kb2 * m_hc1) / m_kb0; // -128..127
m_ha1 = m_ha0;
m_ha0 = sample;
m_hb1 = m_hb0;
m_hb0 = hbn;
m_hc1 = m_hc0;
m_hc0 = hcn;
double env = hbn * m_env; // -32768..32767
double vol = env * m_vol_latch; // -8388608..8388607
buf.put(sampindex, vol / 8388608);
}
}
else
{
m_ha0 = m_ha1 = 0;
m_hb0 = m_hb1 = 0;
m_hc0 = m_hc1 = 0;
outputs[0].fill(0);
}
}
@ -224,6 +265,7 @@ void cmi01a_device::pitch_octave_w(u8 data)
m_pitch &= 0x0ff;
m_pitch |= (data & 3) << 8;
m_octave = (data >> 2) & 0x0f;
update_filters();
}
u8 cmi01a_device::pitch_octave_r()
@ -600,6 +642,52 @@ void cmi01a_device::not_wpe_w(int state)
update_upper_wave_addr_load();
}
void cmi01a_device::update_filters()
{
// Filter ADC input level
int fval = (m_octave << 5) + m_flt_latch;
// Calibrated using the graph page 133 of the CMI Mainframe Service Manual
double fc = 6410 * pow(1.02162, fval - 256);
// -6dB cutoff frequency
double f0 = fc * 0.916;
// Secondary filter around there for when the first filter is high
if(fc > 14000)
fc = 14000;
logerror("Filter latch = %02x, octave=%x, fval=%03x, f0 = %g\n", m_flt_latch, m_octave, fval, f0);
double w1 = 2*M_PI*fc;
double w2 = 2*M_PI*fc*1.22474487139159; // sqrt(c1*c2 / (c3*c4)), the ratio between the two cutoff frequencies in the cmi01 configuration of the SSM2045
double a1 = 1.81659021245849; // sqrt(c1*10*c2)/c1
double a2 = 1.48323969741913; // sqrt(c3*10*c4)/c3
// Two stages of order-2 lowpass filters with fixed Q
// H(s) = 1/(m0 * s**2 + m1 * s + 1)
double ma0 = a1/w1;
double ma1 = 1/(w1*w1);
double mb0 = a2/w2;
double mb1 = 1/(w2*w2);
// Convert to z, wrap around f0
double zc = 2*M_PI*f0/tan(M_PI*f0/48000);
double za0 = ma1 * zc*zc;
double za1 = ma0 * zc;
double zb0 = mb1 * zc*zc;
double zb1 = mb0 * zc;
// H(z) = (1 + 2 * z-1 + z-2) / (k0 + k1 * z-1 + k2 * z-2)
m_ka0 = za0 + za1 + 1;
m_ka1 = -2*za0 + 2;
m_ka2 = za0 - za1 + 1;
m_kb0 = zb0 + zb1 + 1;
m_kb1 = -2*zb0 + 2;
m_kb2 = zb0 - zb1 + 1;
}
inline void cmi01a_device::update_upper_wave_addr_load()
{
const bool c10_and_out = (!m_not_wpe && m_gzx);
@ -725,6 +813,7 @@ void cmi01a_device::write(offs_t offset, u8 data)
case 0x6:
m_flt_latch = data;
update_filters();
break;
case 0x8: case 0x9: case 0xa: case 0xb:

15
src/mame/fairlight/cmi01a.h
View File

@ -117,6 +117,7 @@ private:
void set_wave_addr_lsb(const u8 wave_addr_lsb);
void set_wave_addr_msb(const u8 wave_addr_msb);
void set_wave_addr_msb_clock(const bool wave_addr_msb_clock);
void update_filters();
void set_zx(const bool zx);
void update_ptm_c1();
@ -182,6 +183,20 @@ private:
u8 m_rp = 0;
u8 m_ws = 0;
int m_dir = 0;
double m_ha0 = 0;
double m_ha1 = 0;
double m_hb0 = 0;
double m_hb1 = 0;
double m_hc0 = 0;
double m_hc1 = 0;
double m_ka0 = 0;
double m_ka1 = 0;
double m_ka2 = 0;
double m_kb0 = 0;
double m_kb1 = 0;
double m_kb2 = 0;
};
// device type definition