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Add DAC filtering to Midway "Turbo Cheap Squeak" sound hardware. [Lord Nightmare]

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This commit is contained in:
Lord-Nightmare 2020-10-22 19:40:41 -04:00
parent c2fa1ccf18
commit ac452d53d1
2 changed files with 32 additions and 8 deletions
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37
src/mame/audio/midway.cpp
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@ -6,6 +6,15 @@
Functions to emulate general the various Midway sound cards.
TODO: the "Turbo Cheap Squeak" and "Sounds Good" boards are nearly identical
in function, but use different CPUs and Memory maps (The PIA hookup, DAC
and Filter are all exactly the same), so these should probably be combined
into one base class with two subclass device implementations to reduce
duplicated code.
The "Cheap Squeak Deluxe" board in /audio/csd.cpp is also almost identical
to the "Sounds Good" board, and should also be a member of any future
combined class/device implementation.
***************************************************************************/
#include "emu.h"
@ -606,6 +615,7 @@ void midway_sounds_good_device::device_add_mconfig(machine_config &config)
AD7533(config, m_dac, 0); /// ad7533jn.u10
// The DAC filters here are identical to those on the "Turbo Cheap Squeak" and "Cheap Squeak Deluxe" boards.
//LM359 @U2.2, 2nd order MFB low-pass (fc = 5404.717733, Q = 0.625210, gain = -1.000000)
FILTER_BIQUAD(config, m_dac_filter[2]).opamp_mfb_lowpass_setup(RES_K(150), RES_K(82), RES_K(150), CAP_P(470), CAP_P(150)); // R115, R109, R108, C112, C111
m_dac_filter[2]->add_route(ALL_OUTPUTS, *this, 1.0);
@ -665,12 +675,13 @@ void midway_sounds_good_device::device_timer(emu_timer &timer, device_timer_id i
midway_turbo_cheap_squeak_device::midway_turbo_cheap_squeak_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: device_t(mconfig, MIDWAY_TURBO_CHEAP_SQUEAK, tag, owner, clock),
device_mixer_interface(mconfig, *this),
m_cpu(*this, "cpu"),
m_pia(*this, "pia"),
m_dac(*this, "dac"),
m_status(0),
m_dacval(0)
device_mixer_interface(mconfig, *this)
, m_cpu(*this, "cpu")
, m_pia(*this, "pia")
, m_dac(*this, "dac")
, m_dac_filter(*this, "dac_filter%u", 0U)
, m_status(0)
, m_dacval(0)
{
}
@ -769,7 +780,19 @@ void midway_turbo_cheap_squeak_device::device_add_mconfig(machine_config &config
m_pia->irqa_handler().set(FUNC(midway_turbo_cheap_squeak_device::irq_w));
m_pia->irqb_handler().set(FUNC(midway_turbo_cheap_squeak_device::irq_w));
AD7533(config, m_dac, 0).add_route(ALL_OUTPUTS, *this, 1.0);
AD7533(config, m_dac, 0); /// ad7533jn.u11
// The DAC filters here are identical to those on the "Sounds Good" and "Cheap Squeak Deluxe" boards.
//LM359 @U14.2, 2nd order MFB low-pass (fc = 5404.717733, Q = 0.625210, gain = -1.000000)
FILTER_BIQUAD(config, m_dac_filter[2]).opamp_mfb_lowpass_setup(RES_K(150), RES_K(82), RES_K(150), CAP_P(470), CAP_P(150)); // R36, R37, R39, C19, C20
m_dac_filter[2]->add_route(ALL_OUTPUTS, *this, 1.0);
//LM359 @U13.2, 2nd order MFB low-pass (fc = 5310.690763, Q = 1.608630, gain = -1.000000)
FILTER_BIQUAD(config, m_dac_filter[1]).opamp_mfb_lowpass_setup(RES_K(33), RES_K(18), RES_K(33), CAP_P(5600), CAP_P(270)); // R32, R33, R35, C16, C17
m_dac_filter[1]->add_route(ALL_OUTPUTS, m_dac_filter[2], 1.0);
//LM359 @U13.1, 1st order MFB low-pass (fc = 4912.189602, Q = 0.707107(ignored), gain = -1.000000)
FILTER_BIQUAD(config, m_dac_filter[0]).opamp_mfb_lowpass_setup(RES_K(120), RES_K(0), RES_K(120), CAP_P(0), CAP_P(270)); // R27, <short>, R31, <nonexistent>, C14
m_dac_filter[0]->add_route(ALL_OUTPUTS, m_dac_filter[1], 1.0);
m_dac->add_route(ALL_OUTPUTS, m_dac_filter[0], 1.0);
}

3
src/mame/audio/midway.h
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@ -189,7 +189,8 @@ private:
// devices
required_device<mc6809e_device> m_cpu;
required_device<pia6821_device> m_pia;
required_device<dac_word_interface> m_dac;
required_device<ad7533_device> m_dac;
required_device_array<filter_biquad_device, 3> m_dac_filter;
// internal state
uint8_t m_status;