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Change channel_spectrum type to std::complex<float>.

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Move FFT bit-reversal to complex<int16_t> -> complex<float> copy.
Change window so that adjacent bins have constant(-ish) gain.
Change window to float.
Change time domain samples to accumulate at even intervals over the FFT interval.
This commit is contained in:
Jared Boone 2015-09-17 17:37:05 -07:00
parent 882fbbef31
commit 291de8f869
4 changed files with 294 additions and 162 deletions
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10
firmware/baseband/baseband_processor.cpp
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@ -38,14 +38,12 @@ void BasebandProcessor::update_spectrum() {
// Called from idle thread (after EVT_MASK_SPECTRUM is flagged)
if( channel_spectrum_request_update ) {
/* Decimated buffer is full. Compute spectrum. */
std::array<std::complex<float>, 256> samples_swapped;
fft_swap(channel_spectrum, samples_swapped);
channel_spectrum_request_update = false;
fft_c_preswapped(samples_swapped);
fft_c_preswapped(channel_spectrum);
ChannelSpectrumMessage spectrum_message;
for(size_t i=0; i<spectrum_message.spectrum.db.size(); i++) {
const auto mag2 = magnitude_squared(samples_swapped[i]);
const auto mag2 = magnitude_squared(channel_spectrum[i]);
const float db = complex16_mag_squared_to_dbv_norm(mag2);
constexpr float mag_scale = 5.0f;
const unsigned int v = (db * mag_scale) + 255.0f;
@ -102,9 +100,9 @@ void BasebandProcessor::post_channel_stats_message(const ChannelStatistics stati
void BasebandProcessor::post_channel_spectrum_message(const buffer_c16_t data) {
if( !channel_spectrum_request_update ) {
channel_spectrum_request_update = true;
std::copy(&data.p[0], &data.p[data.count], channel_spectrum.begin());
fft_swap(data, channel_spectrum);
channel_spectrum_sampling_rate = data.sampling_rate;
channel_spectrum_request_update = true;
events_flag(EVT_MASK_SPECTRUM);
}
}