portapack-mayhem/firmware/baseband/proc_siggen.cpp
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141 lines
5.2 KiB
C++

/*
* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
* Copyright (C) 2017 Furrtek
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "proc_siggen.hpp"
#include "portapack_shared_memory.hpp"
#include "sine_table_int8.hpp"
#include "event_m4.hpp"
#include <cstdint>
void SigGenProcessor::execute(const buffer_c8_t& buffer) {
if (!configured) return;
for (size_t i = 0; i < buffer.count; i++) {
if (!sample_count && auto_off) {
configured = false;
txprogress_message.done = true;
shared_memory.application_queue.push(txprogress_message);
} else
sample_count--;
if (tone_shape == 0) {
// CW
re = 127;
im = 0;
} else {
if (tone_shape == 1) {
// Sine
sample = (sine_table_i8[(tone_phase & 0xFF000000) >> 24]);
} else if (tone_shape == 2) {
// Triangle
int8_t a = (tone_phase & 0xFF000000) >> 24;
sample = (a & 0x80) ? ((a << 1) ^ 0xFF) - 0x80 : (a << 1) + 0x80;
} else if (tone_shape == 3) {
// Saw up
sample = ((tone_phase & 0xFF000000) >> 24);
} else if (tone_shape == 4) {
// Saw down
sample = ((tone_phase & 0xFF000000) >> 24) ^ 0xFF;
} else if (tone_shape == 5) {
// Square
sample = (((tone_phase & 0xFF000000) >> 24) & 0x80) ? 127 : -128;
} 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, 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); // 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 .
}
if (counter == 10) {
sample = ((lfsr_16 & 0b0001111111100000) >> 5); // just changing the spectrum shape .
}
counter++;
if (counter == 15) {
counter = 0;
}
}
if (tone_shape < 6) { // we are in periodic signals, we need tone phases update.
tone_phase += tone_delta;
}
// 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]);
}
buffer.p[i] = {re, im};
}
};
void SigGenProcessor::on_message(const Message* const msg) {
const auto message = *reinterpret_cast<const SigGenConfigMessage*>(msg);
switch (msg->id) {
case Message::ID::SigGenConfig:
if (!message.bw) {
configured = false;
return;
}
if (message.duration) {
sample_count = message.duration;
auto_off = true;
} else
auto_off = false;
fm_delta = message.bw * (0xFFFFFFULL / 1536000);
tone_shape = message.shape;
// lfsr = seed_value ; // Finally not used , init lfsr 8 bits.
lfsr_16 = seed_value_16; // init lfsr 16 bits.
configured = true;
break;
case Message::ID::SigGenTone:
tone_delta = reinterpret_cast<const SigGenToneMessage*>(msg)->tone_delta;
break;
default:
break;
}
}
int main() {
EventDispatcher event_dispatcher{std::make_unique<SigGenProcessor>()};
event_dispatcher.run();
return 0;
}