From fcd267a3f9655d8ba6eb324481dfdf603ed7d1cd Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 26 Jun 2021 23:48:53 -0400
Subject: [PATCH] Starts implementing noise.

---
 Machines/Enterprise/Dave.cpp | 36 ++++++++++++++++++++++++++----------
 Machines/Enterprise/Dave.hpp | 29 +++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/Machines/Enterprise/Dave.cpp b/Machines/Enterprise/Dave.cpp
index 224764c5b..d3bffe7c5 100644
--- a/Machines/Enterprise/Dave.cpp
+++ b/Machines/Enterprise/Dave.cpp
@@ -26,26 +26,36 @@ void Dave::write(uint16_t address, uint8_t value) {
 				channels_[address >> 1].high_pass = value & 0x40;
 				channels_[address >> 1].ring_modulate = value & 0x80;
 			break;
+			case 6:
+				noise_.frequency = Noise::Frequency(value&3);
+				noise_.polynomial = Noise::Polynomial((value >> 2)&3);
+				noise_.swap_polynomial = value & 0x10;
+				noise_.low_pass = value & 0x20;
+				noise_.high_pass = value & 0x40;
+				noise_.ring_modulate = value & 0x80;
+			break;
 
 			// TODO:
 			//
-			//	6:	noise selection.
-			//	7:	sync bits, optional D/As, interrupt rate (albeit some of that shouldn't be on this thread, or possibly even _here_).
-			//	11, 14:	noise amplitude.
+			//	7:	sync bits, optional D/As.
+			//
+			//		(will handle interrupt bits elsewhere)
 
 			case 8: case 9: case 10:
 				channels_[address - 8].amplitude[0] = value & 0x3f;
 			break;
-			case 11: case 12: case 13:
-				channels_[address - 11].amplitude[1] = value & 0x3f;
+			case 12: case 13: case 14:
+				channels_[address - 12].amplitude[1] = value & 0x3f;
 			break;
+			case 11:	noise_.amplitude[0] = value & 0x3f;		break;
+			case 15:	noise_.amplitude[1] = value & 0x3f;		break;
 		}
 	});
 }
 
 void Dave::set_sample_volume_range(int16_t range) {
 	audio_queue_.defer([range, this] {
-		volume_ = range / (63*3);
+		volume_ = range / (63*4);
 	});
 }
 
@@ -54,9 +64,11 @@ void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
 		poly_state_[int(Channel::Distortion::FourBit)] = poly4_.next();
 		poly_state_[int(Channel::Distortion::FiveBit)] = poly5_.next();
 		poly_state_[int(Channel::Distortion::SevenBit)] = poly7_.next();
+		if(noise_.swap_polynomial) {
+			poly_state_[int(Channel::Distortion::SevenBit)] = poly_state_[int(Channel::Distortion::None)];
+		}
 
-		// TODO: substitute poly_state_[2] if polynomial substitution is in play.
-
+		// Update tone channels.
 #define update_channel(x) {									\
 		auto output = channels_[x].output & 1;				\
 		channels_[x].output <<= 1;							\
@@ -86,19 +98,23 @@ void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
 
 #undef update_channel
 
+		// TODO: update noise channel.
+
 		// Dumbest ever first attempt: sum channels.
 		target[(c << 1) + 0] =
 			volume_ * (
 				channels_[0].amplitude[0] * (channels_[0].output & 1) +
 				channels_[1].amplitude[0] * (channels_[1].output & 1) +
-				channels_[2].amplitude[0] * (channels_[2].output & 1)
+				channels_[2].amplitude[0] * (channels_[2].output & 1) +
+				noise_.amplitude[0] * noise_.output
 			);
 
 		target[(c << 1) + 1] =
 			volume_ * (
 				channels_[0].amplitude[1] * (channels_[0].output & 1) +
 				channels_[1].amplitude[1] * (channels_[1].output & 1) +
-				channels_[2].amplitude[1] * (channels_[2].output & 1)
+				channels_[2].amplitude[1] * (channels_[2].output & 1) +
+				noise_.amplitude[1] * noise_.output
 			);
 	}
 }
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index 3d7c3619b..1f52bb2f6 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -35,6 +35,7 @@ class Dave: public Outputs::Speaker::SampleSource {
 	private:
 		Concurrency::DeferringAsyncTaskQueue &audio_queue_;
 
+		// Tone channels.
 		struct Channel {
 			// User-set values.
 			uint16_t reload = 0;
@@ -52,6 +53,34 @@ class Dave: public Outputs::Speaker::SampleSource {
 			uint16_t count = 0;
 			int output = 0;
 		} channels_[3];
+
+		// Noise channel.
+		struct Noise {
+			// User-set values.
+			uint8_t amplitude[2]{};
+			enum class Frequency {
+				DivideByFour,
+				ToneChannel0,
+				ToneChannel1,
+				ToneChannel2,
+			} frequency = Frequency::DivideByFour;
+			enum class Polynomial {
+				SeventeenBit,
+				FifteenBit,
+				ElevenBit,
+				NineBit
+			} polynomial = Polynomial::SeventeenBit;
+			bool swap_polynomial = false;
+			bool low_pass = false;
+			bool high_pass = false;
+			bool ring_modulate = false;
+
+			// Current state.
+			bool output = false;
+			uint16_t count = 0;
+		} noise_;
+
+		// Global volume, per SampleSource obligations.
 		int16_t volume_ = 0;
 
 		// Polynomials that are always running.