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Solving Noise generation in Signal gen App

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Brumi-2021 2023-04-30 18:03:40 +02:00
parent cb93f2636e
commit ee53b28e60
3 changed files with 42 additions and 26 deletions
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35
firmware/baseband/proc_siggen.cpp
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@ -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;