From ee53b28e60ca272ff8ba5f6913ad635a6aa64dde Mon Sep 17 00:00:00 2001
From: Brumi-2021 <ea3hqj@gmail.com>
Date: Sun, 30 Apr 2023 18:03:40 +0200
Subject: [PATCH] Solving Noise generation in Signal gen App

---
 firmware/application/apps/ui_siggen.hpp | 22 +++++++++-------
 firmware/baseband/proc_siggen.cpp       | 35 ++++++++++++++++---------
 firmware/baseband/proc_siggen.hpp       | 11 ++++----
 3 files changed, 42 insertions(+), 26 deletions(-)

diff --git a/firmware/application/apps/ui_siggen.hpp b/firmware/application/apps/ui_siggen.hpp
index f55d19d1..58ed49b8 100644
--- a/firmware/application/apps/ui_siggen.hpp
+++ b/firmware/application/apps/ui_siggen.hpp
@@ -48,14 +48,16 @@ private:
 	void update_tone();
 	void on_tx_progress(const uint32_t progress, const bool done);
 	
-	const std::string shape_strings[7] = {
-		"CW",
-		"Sine",
-		"Triangle",
-		"Saw up",
-		"Saw down",
-		"Square",
-		"Noise"
+	const std::string shape_strings[9] = {
+		"CW          ",
+		"Sine        ",
+		"Triangle    ",
+		"Saw up      ",
+		"Saw down    ",
+		"Square      ",
+		"Noise n20Khz",
+		"Noise n10khz",
+		"Noise n5khz "
 	};
 	
 	bool auto_update { false };
@@ -78,7 +80,9 @@ private:
 			{ &bitmap_sig_saw_up, 3 },
 			{ &bitmap_sig_saw_down, 4 },
 			{ &bitmap_sig_square, 5 },
-			{ &bitmap_sig_noise, 6 }
+			{ &bitmap_sig_noise, 6 },
+			{ &bitmap_sig_noise, 7 },
+			{ &bitmap_sig_noise, 8 }
 		}
 	};
 	
diff --git a/firmware/baseband/proc_siggen.cpp b/firmware/baseband/proc_siggen.cpp
index dce9d479..2fdc5545 100644
--- a/firmware/baseband/proc_siggen.cpp
+++ b/firmware/baseband/proc_siggen.cpp
@@ -49,7 +49,7 @@ void SigGenProcessor::execute(const buffer_c8_t& buffer) {
 				// Sine
 				sample = (sine_table_i8[(tone_phase & 0xFF000000) >> 24]);
 			} else if (tone_shape == 2) {
-				// Tri
+				// Triangle
 				int8_t a = (tone_phase & 0xFF000000) >> 24;
 				sample = (a & 0x80) ? ((a << 1) ^ 0xFF) - 0x80 : (a << 1) + 0x80;
 			} else if (tone_shape == 3) {
@@ -61,24 +61,34 @@ void SigGenProcessor::execute(const buffer_c8_t& buffer) {
 			} else if (tone_shape == 5) {
 				// Square
 				sample = (((tone_phase & 0xFF000000) >> 24) & 0x80) ? 127 : -128;
-			} else if (tone_shape == 6) {
-				// Noise
-				sample = (lfsr & 0xFF000000) >> 24;
-				feedback = ((lfsr >> 31) ^ (lfsr >> 29) ^ (lfsr >> 15) ^ (lfsr >> 11)) & 1;
-				lfsr = (lfsr << 1) | feedback;
-				if (!lfsr) lfsr = 0x1337;				// Shouldn't do this :(
+			} else if (tone_shape == 6) { // taps: 6 5; feedback polynomial: x^6 + x^5 + 1 , Periode  63 = 2^n-1,it generates armonincs n x 20Khz
+				// White Noise generator, pseudo random noise generator, 8 bits linear-feedback shift register (LFSR) algorithm, variant Fibonacci.
+				// https://en.wikipedia.org/wiki/Linear-feedback_shift_register 
+        		bit = ((lfsr >> 2) ^ (lfsr >> 3)) & 1;	
+		   		lfsr = (lfsr >> 1) | (bit << 7);
+           		sample = lfsr;
+			} else if (tone_shape == 7) { // taps: 7 6; feedback polynomial:  x^7 + x^6 + 1 , Periode 127 = 2^n-1,it generates armonincs n x 10Khz 
+				bit = ((lfsr >> 1) ^ (lfsr >> 2)) & 1;	
+				lfsr = (lfsr >> 1) | (bit << 7);
+           		sample = lfsr;
+			} else if (tone_shape == 8) { //taps:8,6,5,4;feedback polynomial: x^8 + x^6 + x^5 + x^4 + 1,Periode 255= 2^n-1, armonics  n x 5khz
+				bit = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 4))  & 1;	
+        		lfsr = (lfsr >> 1) | (bit << 7);
+           		sample = lfsr;
+			} 
+
+			if (tone_shape < 6) 	{
+				tone_phase += tone_delta;
 			}
 			
-			tone_phase += tone_delta;
-			
-			// Do FM
+			// Do FM modulation
 			delta = sample * fm_delta;
 			
 			phase += delta;
 			sphase = phase + (64 << 24);
 
 			re = (sine_table_i8[(sphase & 0xFF000000) >> 24]);
-			im = (sine_table_i8[(phase & 0xFF000000) >> 24]);
+			im = (sine_table_i8[( phase & 0xFF000000) >> 24]);
 		}
 
 		buffer.p[i] = {re, im};
@@ -104,7 +114,8 @@ void SigGenProcessor::on_message(const Message* const msg) {
 			fm_delta = message.bw * (0xFFFFFFULL / 1536000);
 			tone_shape = message.shape;
 			
-			lfsr = 0x54DF0119;
+			// lfsr = 0x54DF0119;
+			 lfsr = seed_value ;  
 
 			configured = true;
 			break;
diff --git a/firmware/baseband/proc_siggen.hpp b/firmware/baseband/proc_siggen.hpp
index f547cc0f..c4adcd8b 100644
--- a/firmware/baseband/proc_siggen.hpp
+++ b/firmware/baseband/proc_siggen.hpp
@@ -38,13 +38,14 @@ private:
 	
 	BasebandThread baseband_thread { 1536000, this, NORMALPRIO + 20, baseband::Direction::Transmit };
 	
-	uint32_t tone_delta { 0 }, fm_delta { };
-	uint32_t lfsr { }, feedback { }, tone_shape { };
+	uint32_t tone_delta { 0 }, fm_delta { },tone_phase { 0 };
+	uint8_t tone_shape { };
     uint32_t sample_count { 0 };
     bool auto_off { };
-	uint32_t tone_phase { 0 }, phase { 0 }, delta { 0 }, sphase { 0 };
-	int8_t sample { 0 };
-	int8_t re { 0 }, im { 0 };
+	int32_t phase { 0 }, sphase { 0 }, delta { 0 }; 	// they may have sign .
+	int8_t  sample { 0 }, re { 0 }, im { 0 };			// they may have sign .
+    uint8_t seed_value = {0x56};   						// seed : any nonzero start state will work. 
+	uint8_t lfsr { }, bit { };  						// bit must be 8-bit to allow bit<<7 later in the code */
 	
 	TXProgressMessage txprogress_message { };
 };