53 lines
1.9 KiB
Python
53 lines
1.9 KiB
Python
from csdr.chain import Chain
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from pycsdr.modules import Shift, FirDecimate, Bandpass, Squelch, FractionalDecimator, Writer
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from pycsdr.types import Format
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class DemodulatorChain(Chain):
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def __init__(self, samp_rate: int, audioRate: int, shiftRate: float, demodulator: Chain):
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self.shift = Shift(shiftRate)
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decimation, fraction = self._getDecimation(samp_rate, audioRate)
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if_samp_rate = samp_rate / decimation
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transition = 0.15 * (if_samp_rate / float(samp_rate))
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self.decimation = FirDecimate(decimation, transition)
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bp_transition = 320.0 / audioRate
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self.bandpass = Bandpass(transition=bp_transition, use_fft=True)
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readings_per_second = 4
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# s-meter readings are available every 1024 samples
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# the reporting interval is measured in those 1024-sample blocks
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self.squelch = Squelch(5, int(audioRate / (readings_per_second * 1024)))
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workers = [self.shift, self.decimation]
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if fraction != 1.0:
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workers += [FractionalDecimator(Format.COMPLEX_FLOAT, fraction)]
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workers += [self.bandpass, self.squelch, demodulator]
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super().__init__(*workers)
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def setShiftRate(self, rate: float):
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self.shift.setRate(rate)
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def setSquelchLevel(self, level: float):
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self.squelch.setSquelchLevel(level)
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def setBandpass(self, low_cut: float, high_cut: float):
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self.bandpass.setBandpass(low_cut, high_cut)
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def setPowerWriter(self, writer: Writer):
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self.squelch.setPowerWriter(writer)
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def _getDecimation(self, input_rate, output_rate):
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if output_rate <= 0:
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raise ValueError("invalid output rate: {rate}".format(rate=output_rate))
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decimation = 1
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target_rate = output_rate
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while input_rate / (decimation + 1) >= target_rate:
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decimation += 1
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fraction = float(input_rate / decimation) / output_rate
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return decimation, fraction
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