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Consolidate anti_alias BW selection into function (#1217)

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Kyle Reed 2023-06-29 22:35:35 -07:00 • committed by GitHub
parent 2390d79111
commit 99809c7919
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6 changed files with 39 additions and 92 deletions
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31
firmware/application/ui/ui_spectrum.cpp
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@ -367,4 +367,35 @@ void WaterfallView::on_audio_spectrum() {
}
} /* namespace spectrum */
uint32_t filter_bandwidth_for_sampling_rate(int32_t sampling_rate) {
switch (sampling_rate) { // Use the var fs (sampling_rate) to set up BPF aprox < fs_max / 2 by Nyquist theorem.
case 0 ... 2000000: // BW Captured range (0 <= 250kHz max) fs = 8 x 250 kHz.
return 1750000; // Minimum BPF MAX2837 for all those lower BW options.
case 4000000 ... 6000000: // BW capture range (500k...750kHz max) fs_max = 8 x 750kHz = 6Mhz
// BW 500k...750kHz, ex. 500kHz (fs = 8 x BW = 4Mhz), BW 600kHz (fs = 4,8Mhz), BW 750 kHz (fs = 6Mhz).
return 2500000; // In some IC, MAX2837 appears as 2250000, but both work similarly.
case 8800000: // BW capture 1,1Mhz fs = 8 x 1,1Mhz = 8,8Mhz. (1Mhz showed slightly higher noise background).
return 3500000;
case 14000000: // BW capture 1,75Mhz, fs = 8 x 1,75Mhz = 14Mhz
// Good BPF, good matching, but LCD flickers, refresh rate should be < 20 Hz, reasonable picture.
return 5000000;
case 16000000: // BW capture 2Mhz, fs = 8 x 2Mhz = 16Mhz
// Good BPF, good matching, but LCD flickers, refresh rate should be < 20 Hz, reasonable picture.
return 6000000;
case 20000000: // BW capture 2,5Mhz, fs = 8 x 2,5 Mhz = 20Mhz
// Good BPF, good matching, but LCD flickers, refresh rate should be < 20 Hz, reasonable picture.
return 7000000;
default: // BW capture 2,75Mhz, fs = 8 x 2,75Mhz = 22Mhz max ADC sampling and others.
// We tested also 9Mhz FPB slightly too much noise floor, better at 8Mhz.
return 8000000;
}
}
} /* namespace ui */