mayhem-firmware/firmware/baseband/dsp_demodulate.cpp
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/*
* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
*
* 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 "dsp_demodulate.hpp"
#include "complex.hpp"
#include "fxpt_atan2.hpp"
#include "utility_m4.hpp"
#include <hal.h>
namespace dsp {
namespace demodulate {
buffer_f32_t AM::execute(
const buffer_c16_t& src,
const buffer_f32_t& dst) {
const void* src_p = src.p;
const auto src_end = &src.p[src.count];
auto dst_p = dst.p;
while (src_p < src_end) {
const uint32_t sample0 = *__SIMD32(src_p)++;
const uint32_t sample1 = *__SIMD32(src_p)++;
const uint32_t mag_sq0 = __SMUAD(sample0, sample0);
const uint32_t mag_sq1 = __SMUAD(sample1, sample1);
*(dst_p++) = __builtin_sqrtf(mag_sq0) * k;
*(dst_p++) = __builtin_sqrtf(mag_sq1) * k;
}
return {dst.p, src.count, src.sampling_rate};
}
buffer_f32_t SSB::execute(
const buffer_c16_t& src,
const buffer_f32_t& dst) {
const complex16_t* src_p = src.p;
const auto src_end = &src.p[src.count];
auto dst_p = dst.p;
while (src_p < src_end) {
*(dst_p++) = (src_p++)->real() * k;
*(dst_p++) = (src_p++)->real() * k;
*(dst_p++) = (src_p++)->real() * k;
*(dst_p++) = (src_p++)->real() * k;
}
return {dst.p, src.count, src.sampling_rate};
}
/*
static inline float angle_approx_4deg0(const complex32_t t) {
const auto x = static_cast<float>(t.imag()) / static_cast<float>(t.real());
return 16384.0f * x;
}
*/
static inline float angle_approx_0deg27(const complex32_t t) {
if (t.real()) {
const auto x = static_cast<float>(t.imag()) / static_cast<float>(t.real());
return x / (1.0f + 0.28086f * x * x);
} else {
return (t.imag() < 0) ? -1.5707963268f : 1.5707963268f;
}
}
static inline float angle_precise(const complex32_t t) {
return atan2f(t.imag(), t.real());
}
buffer_f32_t FM::execute(
const buffer_c16_t& src,
const buffer_f32_t& dst) {
auto z = z_;
const void* src_p = src.p;
const auto src_end = &src.p[src.count];
auto dst_p = dst.p;
while (src_p < src_end) {
const auto s0 = *__SIMD32(src_p)++;
const auto s1 = *__SIMD32(src_p)++;
const auto t0 = multiply_conjugate_s16_s32(s0, z);
const auto t1 = multiply_conjugate_s16_s32(s1, s0);
z = s1;
*(dst_p++) = angle_precise(t0) * kf;
*(dst_p++) = angle_precise(t1) * kf;
}
z_ = z;
return {dst.p, src.count, src.sampling_rate};
}
buffer_s16_t FM::execute(
const buffer_c16_t& src,
const buffer_s16_t& dst) {
auto z = z_;
const void* src_p = src.p;
const auto src_end = &src.p[src.count];
void* dst_p = dst.p;
while (src_p < src_end) {
const auto s0 = *__SIMD32(src_p)++;
const auto s1 = *__SIMD32(src_p)++;
const auto t0 = multiply_conjugate_s16_s32(s0, z);
const auto t1 = multiply_conjugate_s16_s32(s1, s0);
z = s1;
const int32_t theta0_int = angle_approx_0deg27(t0) * ks16;
const int32_t theta0_sat = __SSAT(theta0_int, 16);
const int32_t theta1_int = angle_approx_0deg27(t1) * ks16;
const int32_t theta1_sat = __SSAT(theta1_int, 16);
*__SIMD32(dst_p)++ = __PKHBT(
theta0_sat,
theta1_sat,
16);
}
z_ = z;
return {dst.p, src.count, src.sampling_rate};
}
void FM::configure(const float sampling_rate, const float deviation_hz) {
/*
* angle: -pi to pi. output range: -32768 to 32767.
* Maximum delta-theta (output of atan2) at maximum deviation frequency:
* delta_theta_max = 2 * pi * deviation / sampling_rate
*/
kf = static_cast<float>(1.0f / (2.0 * pi * deviation_hz / sampling_rate));
ks16 = 32767.0f * kf;
}
} // namespace demodulate
} // namespace dsp