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Added different modulations in signal generator (#2492)

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* Added DSB, AM 100% mod index and AM 50% mod index. Changed UI.
This commit is contained in:
Davide Rovelli
2025-01-26 21:41:11 +01:00
committed by GitHub
parent 5bd208bca1
commit 520ad97f78
4 changed files with 136 additions and 85 deletions
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115
firmware/baseband/proc_siggen.cpp
View File

@@ -38,28 +38,67 @@ void SigGenProcessor::execute(const buffer_c8_t& buffer) {
} else
sample_count--;
if (tone_shape == 0) {
if (modulation == 0) {
// CW
re = 127; // max. signed 8 bits value . (-128 ...+127), max. amplitude , static phasor at 0º
im = 0;
} else {
if (tone_shape == 1) {
} else if (modulation == 2) {
// Digital BPSK consecutive 0,1,0,...continuous cycle, 1 bit/symbol, at rate of 2 symbols / Freq Tone Periode... without any Pulse shape at the moment .
re = (((tone_phase & 0xFF000000) >> 24) & 0x80) ? 127 : -128; // Sending 2 bits by Periode T of the GUI tone, alternative static phasor to 0, -180º , 0º
im = 0;
tone_phase += tone_delta; // In BPSK-QSPK we are using to calculate each 1/4 of the periode.
} else if (modulation == 3) {
// Digital QPSK consecutive 00, 01, 10, 11,00, ...continuous cycle ,2 bits/symbol, at rate of 4 symbols / Freq Tone Periode. not random., without any Pulse shape at the moment .
switch (((tone_phase & 0xFF000000) >> 24)) {
case 0 ... 63: // equivalent to 1/4 of total 360º degrees.
/* "00" */
re = (sine_table_i8[32]); // we are sending symbol-phasor 45º during 1/4 of the total periode
im = (sine_table_i8[32 + 64]); // 32 index = rounded (45º/360º * 255 total sin table steps) = 31,875
break;
case 64 ... 127:
/* "01" */
re = (sine_table_i8[96]); // symbol-phasor 135º
im = (sine_table_i8[96 + 64]); // 96 index = 32 + 256/4
break;
break;
case 128 ... 191:
/* "10" */
re = (sine_table_i8[159]); // symbol-phasor 225º
im = (sine_table_i8[159 + 64]); // 159 rounded index = 96 + 256/4 = 159.3
break;
case 192 ... 255:
/* "11" */
re = (sine_table_i8[223]); // symbol-phasor 315º ; 223 rounded index = (315/360) * 255 =223.125
im = (sine_table_i8[((223 + 64) & 0xFF)]); // Max index 255, circular periodic conversion.
break;
default:
break;
}
tone_phase += tone_delta; // In BPSK-QSPK we are using to calculate each 1/4 of the periode.
} else { // Other modulations: FM, DSB, AM
if (tone_shape == 0) {
// Sine
sample = (sine_table_i8[(tone_phase & 0xFF000000) >> 24]);
} else if (tone_shape == 2) {
} else if (tone_shape == 1) {
// Triangle
int8_t a = (tone_phase & 0xFF000000) >> 24;
sample = (a & 0x80) ? ((a << 1) ^ 0xFF) - 0x80 : (a << 1) + 0x80;
} else if (tone_shape == 3) {
} else if (tone_shape == 2) {
// Saw up
sample = ((tone_phase & 0xFF000000) >> 24);
} else if (tone_shape == 4) {
} else if (tone_shape == 3) {
// Saw down
sample = ((tone_phase & 0xFF000000) >> 24) ^ 0xFF;
} else if (tone_shape == 5) {
} else if (tone_shape == 4) {
// Square
sample = (((tone_phase & 0xFF000000) >> 24) & 0x80) ? 127 : -128;
} else if (tone_shape == 6) {
} else if (tone_shape == 5) {
// 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
@@ -79,49 +118,13 @@ void SigGenProcessor::execute(const buffer_c8_t& buffer) {
if (counter == 15) {
counter = 0;
}
} else if (tone_shape == 7) {
// Digital BPSK consecutive 0,1,0,...continuous cycle, 1 bit/symbol, at rate of 2 symbols / Freq Tone Periode... without any Pulse shape at the moment .
re = (((tone_phase & 0xFF000000) >> 24) & 0x80) ? 127 : -128; // Sending 2 bits by Periode T of the GUI tone, alternative static phasor to 0, -180º , 0º
im = 0;
} else if (tone_shape == 8) {
// Digital QPSK consecutive 00, 01, 10, 11,00, ...continuous cycle ,2 bits/symbol, at rate of 4 symbols / Freq Tone Periode. not random., without any Pulse shape at the moment .
switch (((tone_phase & 0xFF000000) >> 24)) {
case 0 ... 63: // equivalent to 1/4 of total 360º degrees.
/* "00" */
re = (sine_table_i8[32]); // we are sending symbol-phasor 45º during 1/4 of the total periode
im = (sine_table_i8[32 + 64]); // 32 index = rounded (45º/360º * 255 total sin table steps) = 31,875
break;
case 64 ... 127:
/* "01" */
re = (sine_table_i8[96]); // symbol-phasor 135º
im = (sine_table_i8[96 + 64]); // 96 index = 32 + 256/4
break;
break;
case 128 ... 191:
/* "10" */
re = (sine_table_i8[159]); // symbol-phasor 225º
im = (sine_table_i8[159 + 64]); // 159 rounded index = 96 + 256/4 = 159.3
break;
case 192 ... 255:
/* "11" */
re = (sine_table_i8[223]); // symbol-phasor 315º ; 223 rounded index = (315/360) * 255 =223.125
im = (sine_table_i8[((223 + 64) & 0xFF)]); // Max index 255, circular periodic conversion.
break;
default:
break;
}
}
if (tone_shape != 6) { //(all except Pseudo Random White Noise). We are in (1):periodic signals or (2):BPSK/QPSK , in both cases ,we need Tone updated acum sum phases to modulate in FM / or control phasor phase (BPSK & QPSK.)
tone_phase += tone_delta; // In periodic signals(Sine/triangle/square) we are using to FM mod. in BPSK-QSPK we are using to calculate each 1/4 of the periode.
if (tone_shape != 5) { // All periodic except Pseudo Random White Noise.
tone_phase += tone_delta; // In periodic signals we are using phase to generate the tone to be modulated.
}
if (tone_shape < 7) { // All Option shape signals except BPSK(7) & QPSK(8) we are modulating in FM. (Those two has phase shift modulation XPSK , not FM )
if (modulation == 1) {
// Do FM modulation
delta = sample * fm_delta;
@@ -130,6 +133,21 @@ void SigGenProcessor::execute(const buffer_c8_t& buffer) {
re = (sine_table_i8[(sphase & 0xFF000000) >> 24]); // sin LUT is not dealing with decimals , output range [-128 ,...127]
im = (sine_table_i8[(phase & 0xFF000000) >> 24]);
} else if (modulation == 4) {
// Do Double Side Band modulation
re = sample;
im = 0;
} else if (modulation == 5) {
// Do AM modulation (100% mod index)
re = (127 >> 1) + (sample >> 1);
im = 0;
} else if (modulation == 6) {
// Do AM modulation (50% mod index)
re = 95 + (sample >> 2);
im = 0;
}
}
@@ -154,7 +172,8 @@ void SigGenProcessor::on_message(const Message* const msg) {
auto_off = false;
fm_delta = message.bw * (0xFFFFFFULL / 1536000);
tone_shape = message.shape;
tone_shape = message.shape & 0xF;
modulation = (message.shape & 0xF0) >> 4;
// lfsr = seed_value ; // Finally not used , init lfsr 8 bits.
lfsr_16 = seed_value_16; // init lfsr 16 bits.

2
firmware/baseband/proc_siggen.hpp
View File

@@ -36,7 +36,7 @@ class SigGenProcessor : public BasebandProcessor {
bool configured{false};
uint32_t tone_delta{0}, fm_delta{}, tone_phase{0};
uint8_t tone_shape{};
uint8_t tone_shape{}, modulation{};
uint32_t sample_count{0};
bool auto_off{};
int32_t phase{0}, sphase{0}, delta{0}; // they may have sign in the pseudo random sample generation.