mirror of https://github.com/gnss-sdr/gnss-sdr
235 lines
7.7 KiB
C++
235 lines
7.7 KiB
C++
/*!
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* \file gps_l1_ca_pcps_acquisition_fpga.cc
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* \brief Adapts a PCPS acquisition block to an AcquisitionInterface
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* for GPS L1 C/A signals for the FPGA
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* \authors <ul>
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* <li> Marc Majoral, 2019. mmajoral(at)cttc.es
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* <li> Javier Arribas, 2019. jarribas(at)cttc.es
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* </ul>
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*
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* -----------------------------------------------------------------------------
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*
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* GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
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* This file is part of GNSS-SDR.
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*
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* Copyright (C) 2010-2022 (see AUTHORS file for a list of contributors)
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -----------------------------------------------------------------------------
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*/
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#include "gps_l1_ca_pcps_acquisition_fpga.h"
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#include "GPS_L1_CA.h"
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#include "configuration_interface.h"
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#include "gnss_sdr_fft.h"
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#include "gnss_sdr_flags.h"
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#include "gps_sdr_signal_replica.h"
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#include <glog/logging.h>
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#include <gnuradio/gr_complex.h> // for gr_complex
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#include <volk/volk.h> // for volk_32fc_conjugate_32fc
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#include <algorithm> // for copy_n
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#include <cmath> // for abs, pow, floor
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#include <complex> // for complex
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GpsL1CaPcpsAcquisitionFpga::GpsL1CaPcpsAcquisitionFpga(
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const ConfigurationInterface* configuration,
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const std::string& role,
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unsigned int in_streams,
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unsigned int out_streams) : gnss_synchro_(nullptr),
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role_(role),
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doppler_center_(0),
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channel_(0),
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doppler_step_(0),
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in_streams_(in_streams),
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out_streams_(out_streams)
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{
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acq_parameters_.SetFromConfiguration(configuration, role, fpga_buff_num, fpga_blk_exp, GPS_L1_CA_CODE_RATE_CPS, GPS_L1_CA_CODE_LENGTH_CHIPS);
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DLOG(INFO) << "role " << role;
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if (FLAGS_doppler_max != 0)
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{
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acq_parameters_.doppler_max = FLAGS_doppler_max;
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}
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doppler_max_ = acq_parameters_.doppler_max;
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doppler_step_ = static_cast<unsigned int>(acq_parameters_.doppler_step);
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fs_in_ = acq_parameters_.fs_in;
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uint32_t code_length = acq_parameters_.code_length;
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uint32_t nsamples_total = acq_parameters_.samples_per_code;
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// compute all the GPS L1 PRN Codes (this is done only once upon the class constructor in order to avoid re-computing the PRN codes every time
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// a channel is assigned)
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auto fft_if = gnss_fft_fwd_make_unique(nsamples_total);
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// allocate memory to compute all the PRNs and compute all the possible codes
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volk_gnsssdr::vector<std::complex<float>> code(nsamples_total);
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volk_gnsssdr::vector<std::complex<float>> fft_codes_padded(nsamples_total);
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d_all_fft_codes_ = volk_gnsssdr::vector<uint32_t>(nsamples_total * NUM_PRNs); // memory containing all the possible fft codes for PRN 0 to 32
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float max;
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int32_t tmp;
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int32_t tmp2;
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int32_t local_code;
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int32_t fft_data;
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// temporary maxima search
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for (uint32_t PRN = 1; PRN <= NUM_PRNs; PRN++)
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{
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gps_l1_ca_code_gen_complex_sampled(code, PRN, fs_in_, 0); // generate PRN code
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for (uint32_t s = code_length; s < 2 * code_length; s++)
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{
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code[s] = code[s - code_length];
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}
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// fill in zero padding
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for (uint32_t s = 2 * code_length; s < nsamples_total; s++)
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{
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code[s] = std::complex<float>(0.0, 0.0);
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}
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std::copy_n(code.data(), nsamples_total, fft_if->get_inbuf()); // copy to FFT buffer
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fft_if->execute(); // Run the FFT of local code
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volk_32fc_conjugate_32fc(fft_codes_padded.data(), fft_if->get_outbuf(), nsamples_total); // conjugate values
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max = 0; // initialize maximum value
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for (uint32_t i = 0; i < nsamples_total; i++) // search for maxima
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{
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if (std::abs(fft_codes_padded[i].real()) > max)
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{
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max = std::abs(fft_codes_padded[i].real());
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}
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if (std::abs(fft_codes_padded[i].imag()) > max)
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{
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max = std::abs(fft_codes_padded[i].imag());
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}
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}
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// map the FFT to the dynamic range of the fixed point values an copy to buffer containing all FFTs
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// and package codes in a format that is ready to be written to the FPGA
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for (uint32_t i = 0; i < nsamples_total; i++)
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{
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tmp = static_cast<int32_t>(floor(fft_codes_padded[i].real() * (pow(2, quant_bits_local_code - 1) - 1) / max));
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tmp2 = static_cast<int32_t>(floor(fft_codes_padded[i].imag() * (pow(2, quant_bits_local_code - 1) - 1) / max));
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local_code = (tmp & select_lsbits) | ((tmp2 * shl_code_bits) & select_msbits); // put together the real part and the imaginary part
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fft_data = local_code & select_all_code_bits;
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d_all_fft_codes_[i + (nsamples_total * (PRN - 1))] = fft_data;
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}
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}
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// acq_parameters
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acq_parameters_.all_fft_codes = d_all_fft_codes_.data();
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acquisition_fpga_ = pcps_make_acquisition_fpga(acq_parameters_);
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if (in_streams_ > 1)
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{
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LOG(ERROR) << "This implementation only supports one input stream";
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}
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if (out_streams_ > 0)
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{
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LOG(ERROR) << "This implementation does not provide an output stream";
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}
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}
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void GpsL1CaPcpsAcquisitionFpga::stop_acquisition()
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{
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// stop the acquisition and the other FPGA modules.
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acquisition_fpga_->stop_acquisition();
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}
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void GpsL1CaPcpsAcquisitionFpga::set_threshold(float threshold)
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{
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DLOG(INFO) << "Channel " << channel_ << " Threshold = " << threshold;
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acquisition_fpga_->set_threshold(threshold);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_doppler_max(unsigned int doppler_max)
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{
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doppler_max_ = doppler_max;
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acquisition_fpga_->set_doppler_max(doppler_max_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_doppler_step(unsigned int doppler_step)
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{
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doppler_step_ = doppler_step;
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acquisition_fpga_->set_doppler_step(doppler_step_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_doppler_center(int doppler_center)
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{
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doppler_center_ = doppler_center;
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acquisition_fpga_->set_doppler_center(doppler_center_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_gnss_synchro(Gnss_Synchro* gnss_synchro)
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{
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gnss_synchro_ = gnss_synchro;
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acquisition_fpga_->set_gnss_synchro(gnss_synchro_);
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}
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signed int GpsL1CaPcpsAcquisitionFpga::mag()
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{
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return acquisition_fpga_->mag();
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}
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void GpsL1CaPcpsAcquisitionFpga::init()
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{
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acquisition_fpga_->init();
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}
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void GpsL1CaPcpsAcquisitionFpga::set_local_code()
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{
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acquisition_fpga_->set_local_code();
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}
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void GpsL1CaPcpsAcquisitionFpga::reset()
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{
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// this function starts the acquisition process
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acquisition_fpga_->set_active(true);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_state(int state)
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{
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acquisition_fpga_->set_state(state);
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}
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void GpsL1CaPcpsAcquisitionFpga::connect(gr::top_block_sptr top_block)
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{
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if (top_block)
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{ /* top_block is not null */
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};
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// Nothing to connect
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}
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void GpsL1CaPcpsAcquisitionFpga::disconnect(gr::top_block_sptr top_block)
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{
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if (top_block)
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{ /* top_block is not null */
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};
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// Nothing to disconnect
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}
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gr::basic_block_sptr GpsL1CaPcpsAcquisitionFpga::get_left_block()
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{
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return nullptr;
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}
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gr::basic_block_sptr GpsL1CaPcpsAcquisitionFpga::get_right_block()
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{
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return nullptr;
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}
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