From 5a336d5e71c8ad5613ba0676f750daa22e1acd9a Mon Sep 17 00:00:00 2001 From: Brumi-2021 Date: Wed, 3 May 2023 13:49:50 +0200 Subject: [PATCH] Compact with unique, best Noise Gererator option. --- firmware/application/apps/ui_siggen.hpp | 2 +- firmware/baseband/proc_siggen.cpp | 41 ++++++++++--------------- 2 files changed, 18 insertions(+), 25 deletions(-) diff --git a/firmware/application/apps/ui_siggen.hpp b/firmware/application/apps/ui_siggen.hpp index 31954375..bb00ec41 100644 --- a/firmware/application/apps/ui_siggen.hpp +++ b/firmware/application/apps/ui_siggen.hpp @@ -55,7 +55,7 @@ private: "Saw up signal ", "Saw down signal", "Square signal ", - "White Noise " // using 16 bits LFSR register, 16 order polynomial feedback. + "Noise signal " // using 16 bits LFSR register, 16 order polynomial feedback. }; bool auto_update { false }; diff --git a/firmware/baseband/proc_siggen.cpp b/firmware/baseband/proc_siggen.cpp index 810477cf..ea796301 100644 --- a/firmware/baseband/proc_siggen.cpp +++ b/firmware/baseband/proc_siggen.cpp @@ -61,36 +61,29 @@ 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) { // White Noise generator, pseudo random noise generator, 8 bits linear-feedback shift register (LFSR) algorithm, variant Fibonacci. + } else if (tone_shape == 6) { + // Noise generator, pseudo random noise generator, 16 bits linear-feedback shift register (LFSR) algorithm, variant Fibonacci. // https://en.wikipedia.org/wiki/Linear-feedback_shift_register // 16 bits LFSR .taps: 16, 15, 13, 4 ;feedback polynomial: x^16 + x^15 + x^13 + x^4 + 1 - // Periode 65535= 2^n-1, harmonics every < 1Khz , quite continuous . - if (counter == 0) { + // Periode 65535= 2^n-1, quite continuous . + if (counter == 0) { // we slow down the shift register, because the pseudo random noise clock freq was too high for modulator. bit_16 = ((lfsr_16 >> 0) ^ (lfsr_16 >> 1) ^ (lfsr_16 >> 3) ^ (lfsr_16 >> 4) ^ (lfsr_16 >> 12) & 1); lfsr_16 = (lfsr_16 >> 1) | (bit_16 << 15); - sample = (lfsr_16 & 0x00FF); - counter++; - } else { // counter == 1 , no need to shift the register again, just use the top 8 bits. - // sample = ((lfsr_16 & 0XFF00) >> 8); // it becomes less continuous the spectrum. Better skip it . - counter = 0; + sample = (lfsr_16 & 0x00FF); // main pseudo random noise generator. + } + if (counter == 5) { // after many empiric test, that combination mix of >>4 and >>5, gives a reasonable trade off white noise / good rf power level . + sample = ((lfsr_16 & 0b0000111111110000) >> 4); // just changing the spectrum shape . } - } - - /* else if (tone_shape == 7) { // 8 bit options, finally not used- - bit = ((lfsr >> 2) ^ (lfsr >> 3)) & 1; // taps: 6 5; feedback polynomial: x^6 + x^5 + 1 , Periode 63 = 2^n-1,it generates armonincs n x 20Khz - lfsr = (lfsr >> 1) | (bit << 7); - sample = lfsr; - } else if (tone_shape == 8) { // 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 == 9) { //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 (counter == 10) { + sample = ((lfsr_16 & 0b0001111111100000) >> 5); // just changing the spectrum shape . + } + counter++; + if (counter ==15) { + counter=0; + } + } - - if (tone_shape < 6) { + if (tone_shape < 6) { // we are in periodic signals, we need tone phases update. tone_phase += tone_delta; }