From f8bb66d2a0c22a363aa233f3ea819b6c492768b7 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 26 Jun 2021 23:39:59 -0400
Subject: [PATCH] Attempts an essentially-complete implementation of tone
 channels.

---
 Machines/Enterprise/Dave.cpp       | 48 +++++++++++++++++++++---------
 Machines/Enterprise/Dave.hpp       | 17 +++++++----
 Machines/Enterprise/Enterprise.cpp |  6 ++--
 3 files changed, 49 insertions(+), 22 deletions(-)

diff --git a/Machines/Enterprise/Dave.cpp b/Machines/Enterprise/Dave.cpp
index 8d5ef6593..224764c5b 100644
--- a/Machines/Enterprise/Dave.cpp
+++ b/Machines/Enterprise/Dave.cpp
@@ -50,15 +50,35 @@ void Dave::set_sample_volume_range(int16_t range) {
 }
 
 void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
-	// Step 1: divide input clock to 125,000 Hz (?)
 	for(size_t c = 0; c < number_of_samples; c++) {
-#define update_channel(x)								\
-		if(!channels_[x].count) {						\
-			channels_[x].output ^= true;				\
-			channels_[x].count = channels_[x].reload;	\
-		} else {										\
-			--channels_[x].count;						\
-		}
+		poly_state_[int(Channel::Distortion::FourBit)] = poly4_.next();
+		poly_state_[int(Channel::Distortion::FiveBit)] = poly5_.next();
+		poly_state_[int(Channel::Distortion::SevenBit)] = poly7_.next();
+
+		// TODO: substitute poly_state_[2] if polynomial substitution is in play.
+
+#define update_channel(x) {									\
+		auto output = channels_[x].output & 1;				\
+		channels_[x].output <<= 1;							\
+		if(!channels_[x].count) {							\
+			channels_[x].count = channels_[x].reload;		\
+															\
+			if(channels_[x].distortion == Channel::Distortion::None)	\
+				output ^= 1;								\
+			else											\
+				output = poly_state_[int(channels_[x].distortion)];	\
+															\
+			if(channels_[x].high_pass && (channels_[(x+1)%3].output&3) == 2) {	\
+				output = 0;									\
+			}												\
+			if(channels_[x].ring_modulate) {				\
+				output = ~(output ^ channels_[(x+2)%3].output) & 1;	\
+			}												\
+		} else {											\
+			--channels_[x].count;							\
+		}													\
+		channels_[x].output |= output;						\
+	}
 
 		update_channel(0);
 		update_channel(1);
@@ -69,16 +89,16 @@ void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
 		// Dumbest ever first attempt: sum channels.
 		target[(c << 1) + 0] =
 			volume_ * (
-				channels_[0].amplitude[0] * channels_[0].output +
-				channels_[1].amplitude[0] * channels_[1].output +
-				channels_[2].amplitude[0] * channels_[2].output
+				channels_[0].amplitude[0] * (channels_[0].output & 1) +
+				channels_[1].amplitude[0] * (channels_[1].output & 1) +
+				channels_[2].amplitude[0] * (channels_[2].output & 1)
 			);
 
 		target[(c << 1) + 1] =
 			volume_ * (
-				channels_[0].amplitude[1] * channels_[0].output +
-				channels_[1].amplitude[1] * channels_[1].output +
-				channels_[2].amplitude[1] * channels_[2].output
+				channels_[0].amplitude[1] * (channels_[0].output & 1) +
+				channels_[1].amplitude[1] * (channels_[1].output & 1) +
+				channels_[2].amplitude[1] * (channels_[2].output & 1)
 			);
 	}
 }
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index 911707431..3d7c3619b 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -41,27 +41,32 @@ class Dave: public Outputs::Speaker::SampleSource {
 			bool high_pass = false;
 			bool ring_modulate = false;
 			enum class Distortion {
-				None,
-				FourBit,
-				FiveBit,
-				SevenBit,
+				None = 0,
+				FourBit = 1,
+				FiveBit = 2,
+				SevenBit = 3,
 			} distortion = Distortion::None;
 			uint8_t amplitude[2]{};
 
 			// Current state.
 			uint16_t count = 0;
-			bool output = true;
+			int output = 0;
 		} channels_[3];
 		int16_t volume_ = 0;
 
-		// Various polynomials that contribute to audio generation.
+		// Polynomials that are always running.
 		Numeric::LFSRv<0xc> poly4_;
 		Numeric::LFSRv<0x14> poly5_;
 		Numeric::LFSRv<0x60> poly7_;
+
+		// The selectable, noise-related polynomial.
 		Numeric::LFSRv<0x110> poly9_;
 		Numeric::LFSRv<0x500> poly11_;
 		Numeric::LFSRv<0x6000> poly15_;
 		Numeric::LFSRv<0x12000> poly17_;
+
+		// Current state of the active polynomials.
+		uint8_t poly_state_[4];
 };
 
 }
diff --git a/Machines/Enterprise/Enterprise.cpp b/Machines/Enterprise/Enterprise.cpp
index bda4eec55..34ff7fcb5 100644
--- a/Machines/Enterprise/Enterprise.cpp
+++ b/Machines/Enterprise/Enterprise.cpp
@@ -210,7 +210,7 @@ template <bool has_disk_controller> class ConcreteMachine:
 			page<3>(0x00);
 
 			// Set up audio.
-			speaker_.set_input_rate(125000.0f);	// TODO: a bigger number, and respect the programmable divider.
+			speaker_.set_input_rate(250000.0f);	// TODO: a bigger number, and respect the programmable divider.
 
 			// Pass on any media.
 			insert_media(target.media);
@@ -368,7 +368,9 @@ template <bool has_disk_controller> class ConcreteMachine:
 		}
 
 		inline void update_audio() {
-			speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(32)));
+			// TODO: divide by only 8, letting Dave divide itself by a further 2 or 3
+			// as per its own register.
+			speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(16)));
 		}
 
 	private: