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Explain and clean up decimator scalars (#1422)

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Kyle Reed 2023-08-30 09:05:49 -07:00 • committed by GitHub
parent 4bc752b7a8
commit f46e20c977
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16 changed files with 51 additions and 73 deletions
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25
firmware/baseband/proc_capture.cpp
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@ -104,43 +104,38 @@ void CaptureProcessor::sample_rate_config(const SampleRateConfigMessage& message
if (sample_rate >= 1'500'000)
spectrum_interval_samples /= (sample_rate / 750'000);
// Mystery scalars for decimator configuration.
// TODO: figure these out and add a real comment.
constexpr int decim_0_scale = 0x2000000;
constexpr int decim_1_scale = 0x20000;
switch (message.oversample_rate) {
case OversampleRate::x4:
// M4 can't handle 2 decimation passes for sample rates needing x4.
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps, decim_0_scale);
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps);
decim_1.set<NoopDecim>();
break;
case OversampleRate::x8:
// M4 can't handle 2 decimation passes for sample rates <= 600k.
if (message.sample_rate < 600'000) {
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps, decim_0_scale);
decim_1.set<FIRC16xR16x16Decim2>().configure(taps_200k_decim_1.taps, decim_1_scale);
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps);
decim_1.set<FIRC16xR16x16Decim2>().configure(taps_200k_decim_1.taps);
} else {
// Using 180k taps to provide better filtering with a single pass.
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_180k_wfm_decim_0.taps, decim_0_scale);
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_180k_wfm_decim_0.taps);
decim_1.set<NoopDecim>();
}
break;
case OversampleRate::x16:
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_200k_decim_0.taps, decim_0_scale);
decim_1.set<FIRC16xR16x16Decim2>().configure(taps_200k_decim_1.taps, decim_1_scale);
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_200k_decim_0.taps);
decim_1.set<FIRC16xR16x16Decim2>().configure(taps_200k_decim_1.taps);
break;
case OversampleRate::x32:
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps, decim_0_scale);
decim_1.set<FIRC16xR16x32Decim8>().configure(taps_16k0_decim_1.taps, decim_1_scale);
decim_0.set<FIRC8xR16x24FS4Decim4>().configure(taps_200k_decim_0.taps);
decim_1.set<FIRC16xR16x32Decim8>().configure(taps_16k0_decim_1.taps);
break;
case OversampleRate::x64:
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_200k_decim_0.taps, decim_0_scale);
decim_1.set<FIRC16xR16x32Decim8>().configure(taps_16k0_decim_1.taps, decim_1_scale);
decim_0.set<FIRC8xR16x24FS4Decim8>().configure(taps_200k_decim_0.taps);
decim_1.set<FIRC16xR16x32Decim8>().configure(taps_16k0_decim_1.taps);
break;
default: