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-rw-r--r--src/devices/sound/dac.cpp119
1 files changed, 118 insertions, 1 deletions
diff --git a/src/devices/sound/dac.cpp b/src/devices/sound/dac.cpp
index c2dfe37ce0a..26d70d308f3 100644
--- a/src/devices/sound/dac.cpp
+++ b/src/devices/sound/dac.cpp
@@ -8,7 +8,7 @@
Binary Weighted Resistor Network, R-2R Ladder & PWM
- Binary, Ones Complement, Twos Complement or Sign Magnitude coding
+ Binary, Ones Complement, or Twos Complement coding
***************************************************************************/
@@ -18,3 +18,120 @@
DEFINE_DEVICE_TYPE(_dac_type, _dac_class, _dac_shortname, _dac_description)
#include "dac.h"
+
+
+//-------------------------------------------------
+// dac_mapper_unsigned - map an unsigned value of
+// the given number of bits to a sample value
+//-------------------------------------------------
+
+sound_stream::sample_t dac_mapper_unsigned(u32 input, u8 bits)
+{
+ sound_stream::sample_t scale = 1.0 / sound_stream::sample_t((bits > 1) ? (1 << bits) : 1);
+ input &= (1 << bits) - 1;
+ return sound_stream::sample_t(input) * scale;
+}
+
+
+//-------------------------------------------------
+// dac_mapper_signed - map a signed (2s complement)
+// value of the given number of bits to a sample value
+//-------------------------------------------------
+
+sound_stream::sample_t dac_mapper_signed(u32 input, u8 bits)
+{
+ return dac_mapper_unsigned(input ^ (1 << (bits - 1)), bits);
+}
+
+
+//-------------------------------------------------
+// dac_mapper_ones_complement - map a value where
+// the top bit indicates the lower bits should be
+// treated as a negative 1s complement
+//-------------------------------------------------
+
+sound_stream::sample_t dac_mapper_ones_complement(u32 input, u8 bits)
+{
+ // this mapping assumes symmetric reference voltages,
+ // which is true for all existing cases
+ if (BIT(input, bits - 1))
+ return 0.5 - 0.5 * dac_mapper_unsigned(~input, bits - 1);
+ else
+ return 0.5 + 0.5 * dac_mapper_unsigned(input, bits - 1);
+}
+
+
+//-------------------------------------------------
+// dac_device_base - constructor
+//-------------------------------------------------
+
+dac_device_base::dac_device_base(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock, u8 bits, dac_mapper_callback mapper, sound_stream::sample_t gain) :
+ device_t(mconfig, type, tag, owner, clock),
+ device_sound_interface(mconfig, *this),
+ m_stream(nullptr),
+ m_curval(0),
+ m_value_map(1 << bits),
+ m_bits(bits),
+ m_mapper(mapper),
+ m_gain(gain),
+ m_range_min((bits == 1) ? 0.0 : -1.0),
+ m_range_max(1.0)
+{
+}
+
+
+//-------------------------------------------------
+// device_start - device startup
+//-------------------------------------------------
+
+void dac_device_base::device_start()
+{
+ // precompute all gain-applied values
+ for (s32 code = 0; code < m_value_map.size(); code++)
+ m_value_map[code] = m_mapper(code, m_bits) * m_gain;
+
+ // determine the number of inputs
+ int inputs = (get_sound_requested_inputs_mask() == 0) ? 0 : 2;
+
+ // large stream buffer to favour emu/sound.cpp resample quality
+ m_stream = stream_alloc(inputs, 1, 48000 * 32);
+
+ // save data
+ save_item(NAME(m_curval));
+}
+
+
+//-------------------------------------------------
+// sound_stream_update - stream updates
+//-------------------------------------------------
+
+void dac_device_base::sound_stream_update(sound_stream &stream)
+{
+ // rails are constant
+ if (stream.input_count() == 0)
+ {
+ stream.fill(0, m_range_min + m_curval * (m_range_max - m_range_min));
+ return;
+ }
+
+ // constant lo, streaming hi
+ if (!BIT(get_sound_requested_inputs_mask(), DAC_INPUT_RANGE_LO))
+ {
+ for (int sampindex = 0; sampindex < stream.samples(); sampindex++)
+ stream.put(0, sampindex, m_range_min + m_curval * (stream.get(DAC_INPUT_RANGE_HI, sampindex) - m_range_min));
+ }
+
+ // constant hi, streaming lo
+ else if (!BIT(get_sound_requested_inputs_mask(), DAC_INPUT_RANGE_HI))
+ {
+ for (int sampindex = 0; sampindex < stream.samples(); sampindex++)
+ stream.put(0, sampindex, stream.get(DAC_INPUT_RANGE_LO, sampindex) + m_curval * (m_range_max - stream.get(DAC_INPUT_RANGE_LO, sampindex)));
+ }
+
+ // both streams provided
+ else
+ {
+ for (int sampindex = 0; sampindex < stream.samples(); sampindex++)
+ stream.put(0, sampindex, stream.get(DAC_INPUT_RANGE_LO, sampindex) + m_curval * (stream.get(DAC_INPUT_RANGE_HI, sampindex) - stream.get(DAC_INPUT_RANGE_LO, sampindex)));
+ }
+}