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Oversample capturing for low bandwidths (#1332)

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* draft_low_bit_rate_solution_Capture_App

* second_draft_dynamic_decim

* Add support for Oversample Rate to capture.

---------

Co-authored-by: Brumi-2021 <ea3hqj@gmail.com>
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Kyle Reed 2023-07-31 08:46:07 -07:00 • committed by GitHub
parent a24b3ad3de
commit d24ff7b3bc
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10 changed files with 132 additions and 43 deletions
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12
firmware/application/apps/capture_app.cpp
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@ -64,13 +64,19 @@ CaptureAppView::CaptureAppView(NavigationView& nav)
/* base_rate is used for FFT calculation and display LCD, and also in recording writing SD Card rate. */
/* ex. sampling_rate values, 4Mhz, when recording 500 kHz (BW) and fs 8 Mhz, when selected 1 Mhz BW ... */
/* ex. recording 500kHz BW to .C16 file, base_rate clock 500kHz x2(I,Q) x 2 bytes (int signed) =2MB/sec rate SD Card */
auto sampling_rate = 8 * base_rate; // Decimation by 8 done on baseband side.
/* Set up proper anti aliasing BPF bandwith in MAX2837 before ADC sampling according to the new added BW Options. */
// For lower bandwidths, (12k5, 16k, 20k), increase the oversample rate to get a higher sample rate.
OversampleRate oversample_rate = base_rate >= 25'000 ? OversampleRate::Rate8x : OversampleRate::Rate16x;
// HackRF suggests a minimum sample rate of 2M.
// Oversampling helps get to higher sample rates when recording lower bandwidths.
uint32_t sampling_rate = toUType(oversample_rate) * base_rate;
// Set up proper anti aliasing BPF bandwidth in MAX2837 before ADC sampling according to the new added BW Options.
auto anti_alias_baseband_bandwidth_filter = filter_bandwidth_for_sampling_rate(sampling_rate);
waterfall.stop();
record_view.set_sampling_rate(sampling_rate);
record_view.set_sampling_rate(sampling_rate, oversample_rate); // NB: Actually updates the baseband.
receiver_model.set_sampling_rate(sampling_rate);
receiver_model.set_baseband_bandwidth(anti_alias_baseband_bandwidth_filter);
waterfall.start();