软件无线电-它如何工作？ 第三部分

 from __future__ import print_function import SoapySDR import numpy as np import struct import sys import time import datetime def wait_for_start(dt): # Wait for the start while True: now = datetime.datetime.now() diff = int((dt - now).total_seconds()) print("{:02d}:{:02d}:{:02d}: Recording will be started after {}m {:02d}s...".format(now.hour, now.minute, now.second, int(diff / 60), diff % 60)) time.sleep(5) if diff <= 1: break def sdr_enumerate(): # Enumerate SDR devices print("SDR devices:") for d in SoapySDR.Device.enumerate(''): print(d) print() def sdr_init(): soapy_device = "rtlsdr" device = SoapySDR.Device({"driver": soapy_device}) channels = list(range(device.getNumChannels(SoapySDR.SOAPY_SDR_RX))) print("Channels:", channels) ch = channels[0] sample_rates = device.listSampleRates(SoapySDR.SOAPY_SDR_RX, ch) print("Sample rates:\n", sample_rates) print("Gain controls:") for gain in device.listGains(SoapySDR.SOAPY_SDR_RX, ch): print(" %s: %s" % (gain, device.getGainRange(SoapySDR.SOAPY_SDR_RX, ch, gain))) frequencies = device.listFrequencies(SoapySDR.SOAPY_SDR_RX, ch) print("Frequencies names:", frequencies) frequency_name = frequencies[0] print("Frequency channel name:", frequency_name) print("Frequency range:", device.getFrequencyRange(SoapySDR.SOAPY_SDR_RX, ch, frequency_name)[0]) print() return device def sdr_record(device, frequency, sample_rate, gain, blocks_count): print("Frequency:", frequency) print("Sample rate:", sample_rate) print("Gain:", gain) channel = 0 # Always for RTL-SDR device.setFrequency(SoapySDR.SOAPY_SDR_RX, channel, "RF", frequency) device.setGain(SoapySDR.SOAPY_SDR_RX, channel, "TUNER", gain) device.setGainMode(SoapySDR.SOAPY_SDR_RX, channel, False) device.setSampleRate(SoapySDR.SOAPY_SDR_RX, channel, sample_rate) data_format = SoapySDR.SOAPY_SDR_CS8 # if 'rtlsdr' in soapy_device or 'hackrf' in soapy_device else SoapySDR.SOAPY_SDR_CS16 stream = device.setupStream(SoapySDR.SOAPY_SDR_RX, data_format, [channel], {}) device.activateStream(stream) block_size = device.getStreamMTU(stream) print("Block size:", block_size) print("Data format:", data_format) print() # IQ: 2 digits ver variable buffer_format = np.int8 buffer_size = 2 * block_size # I + Q samples buffer = np.empty(buffer_size, buffer_format) # Number of blocks to save block, max_blocks = 0, blocks_count # Save to file file_name = "HDSDR_%s_%dkHz_RF.wav" % (datetime.datetime.utcnow().strftime("%Y%m%d_%H%M%SZ"), frequency/1000) print("Saving file:", file_name) with open(file_name, "wb") as wav: # Wav data info bits_per_sample = 16 channels_num, samples_num = 2, int(max_blocks * block_size) subchunk_size = 16 # always 16 for PCM subchunk2_size = int(samples_num * channels_num * bits_per_sample / 8) block_alignment = int(channels_num * bits_per_sample / 8) # Write RIFF header wav.write('RIFF'.encode('utf-8')) wav.write(struct.pack('<i', 4 + (8 + subchunk_size) + (8 + subchunk2_size))) # Size of the overall file wav.write('WAVE'.encode('utf-8')) # Write fmt subchunk wav.write('fmt '.encode('utf-8')) # chunk type wav.write(struct.pack('<i', subchunk_size)) # subchunk data size (16 for PCM) wav.write(struct.pack('<h', 1)) # compression type 1 - PCM wav.write(struct.pack('<h', channels_num)) # channels wav.write(struct.pack('<i', int(sample_rate))) # sample rate wav.write(struct.pack('<i', int(sample_rate * bits_per_sample * channels_num/ 8))) # byte rate wav.write(struct.pack('<h', block_alignment)) # block alignment wav.write(struct.pack('<h', bits_per_sample)) # sample depth # Write data subchunk wav.write('data'.encode('utf-8')) wav.write(struct.pack('<i', subchunk2_size)) while True: d_info = device.readStream(stream, [buffer], buffer_size) if d_info.ret > 0: data = buffer[0:2*d_info.ret] fileData = data if data_format == SoapySDR.SOAPY_SDR_CS8: fileData = data.astype('int16') wav.write(fileData) print("Block %d saved: %d bytes" % (block, 2*d_info.ret)) block += 1 if block > max_blocks: break device.deactivateStream(stream) device.closeStream(stream) if __name__ == "__main__": print("App started") # Forecast for active NOAA satellites # NOAA 15: 137.620, https://www.n2yo.com/passes/?s=25338 # NOAA 18: 137.9125, https://www.n2yo.com/passes/?s=28654 # NOAA 19: 137.100, https://www.n2yo.com/passes/?s=33591 # Wait for the start: 18-May 21:49 21:49: wait_for_start(datetime.datetime(2019, 5, 18, 21, 49, 0)) device = sdr_init() t_start = time.time() sdr_record(device, frequency=137912500, sample_rate=250000, gain=35, blocks_count=2100) print("Recording complete, time = %ds" % int(time.time() - t_start)) print()