RFID library issues - Popping from TX?

Projects LimeSDR
1

Over the last several weeks I’ve been trying to adapt a Gen 2 UHF RFID library that was originally made for the USRPN200/N210 and I’ve at least been able to partially adapt the library, after installing it, for the LimeSDR with the code below:

from gnuradio import eng_notation
from gnuradio import gr
from gnuradio import blocks
from gnuradio import filter
from gnuradio.eng_option import eng_option
from gnuradio.filter import firdes
from optparse import OptionParser
from gnuradio import analog
from gnuradio import digital
import osmosdr
import sip
import sys
import time
import rfid

class reader_top_block(gr.top_block):

  def __init__(self):
    gr.top_block.__init__(self)


    rt = gr.enable_realtime_scheduling()

    ######## Variables #########
    self.dac_rate = 1e6                 # DAC rate
    self.adc_rate = 100e6/50            # ADC rate (2MS/s complex samples)
    self.decim     = 5                    # Decimation (downsampling factor)
    self.ampl     = 0.1                  # Output signal amplitude (signal power vary for different RFX900 cards)
    self.freq     = 915e6                # Modulation frequency (can be set between 902-920)
    self.rx_gain   = 20                   # RX Gain (gain at receiver)
    self.tx_gain   = 0                    # RFX900 no Tx gain option



    # Each FM0 symbol consists of ADC_RATE/BLF samples (2e6/40e3 = 50 samples)
    # 10 samples per symbol after matched filtering and decimation
    self.num_taps     = [1] * 25 # matched to half symbol period

    self.file_sink_decoder        = blocks.file_sink(gr.sizeof_gr_complex*1, "data/decoder", False)
   

    ######## Blocks #########
    self.matched_filter = filter.fir_filter_ccf(self.decim, self.num_taps)
    self.gate            = rfid.gate(int(self.adc_rate/self.decim))
    self.tag_decoder    = rfid.tag_decoder(int(self.adc_rate/self.decim))
    self.reader          = rfid.reader(int(self.adc_rate/self.decim),int(self.dac_rate))
    self.amp              = blocks.multiply_const_ff(self.ampl)
    self.to_complex      = blocks.float_to_complex(1)

    # Osmocom blocks
    self.u_source = osmosdr.source(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0'  )
    self.u_source.set_sample_rate(self.adc_rate)
    self.u_source.set_center_freq(self.freq, 0)
    self.u_source.set_freq_corr(0, 0)
    self.u_source.set_dc_offset_mode(0, 0)
    self.u_source.set_iq_balance_mode(0, 0)
    self.u_source.set_gain_mode(True, 0)
    self.u_source.set_gain(self.rx_gain, 0)
    self.u_source.set_if_gain(10, 0)
    self.u_source.set_bb_gain(10, 0)
    self.u_source.set_antenna("LNAL", 0)
    self.u_source.set_bandwidth(0, 1000000)

    self.u_sink =  osmosdr.sink(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0' )
    self.u_sink.set_sample_rate(self.dac_rate)
    self.u_sink.set_center_freq(self.freq, 0)
    self.u_sink.set_freq_corr(0, 0)
    self.u_sink.set_gain(self.tx_gain, 0)
    self.u_sink.set_if_gain(15, 0)
    self.u_sink.set_bb_gain(15, 0)
    self.u_sink.set_antenna("BAND1", 0)
    self.u_sink.set_bandwidth(0, 1000000)

    ######## Connections #########
    self.connect(self.u_source, self.matched_filter)
    self.connect(self.matched_filter, self.gate)
    self.connect(self.gate, self.tag_decoder)
    self.connect((self.tag_decoder,0), self.reader)
    self.connect(self.reader, self.amp)
    self.connect(self.amp, self.to_complex)
    self.connect(self.to_complex, self.u_sink)

    #self.connect(self.gate, self.file_sink_gate)
    self.connect((self.tag_decoder,1), self.file_sink_decoder) # (Do not comment this line)
    #self.connect(self.file_sink_reader, self.file_sink_reader)
    #self.connect(self.matched_filter, self.file_sink_matched_filter)

if __name__ == '__main__':

  main_block = reader_top_block()
  main_block.start()

  while(1):
    inp = raw_input("'Q' to quit \n")
    if (inp == "q" or inp == "Q"):
      break

  main_block.reader.print_results()
  main_block.stop()

And when I run it I get the following output:

/usr/bin/python2.7 /home/logic/SDR/LimeReader.py
linux; GNU C++ version 5.4.0 20160609; Boost_105800; UHD_003.010.001.001-release

gr::log :INFO: gate0 - T1 samples : 96
gr::log :INFO: gate0 - PW samples : 4
gr::log :INFO: gate0 - Samples of Tag bit : 10
gr::log :INFO: gate0 - Size of window : 100
gr::log :INFO: gate0 - Size of window for dc offset estimation : 48
gr::log :INFO: gate0 - Duration of window for dc offset estimation : 120 us
gr::log :INFO: gate0 - Initializing reader state...
gr::log :INFO: tag_decoder0 - Number of samples of Tag bit : 10
gr::log :INFO: reader0 - Block initialized
gr::log :INFO: reader0 - Number of samples data 0 : 24
gr::log :INFO: reader0 - Number of samples data 1 : 48
gr::log :INFO: reader0 - Number of samples cw : 250
gr::log :INFO: reader0 - Number of samples delim : 12
gr::log :INFO: reader0 - Number of slots : 1
gr::log :INFO: reader0 - Carrier wave after a query transmission in samples : 1295
gr::log :INFO: reader0 - Carrier wave after ACK transmission in samples : 4575
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy soapy redpitaya 
[INFO] Make connection: 'LimeSDR-USB [USB 3.0] 9060A02592E12'
Estimated reference clock 30.7197 MHz
Selected reference clock 30.720 MHz
LMS7002M values cache at /home/logic/.limesuite/LMS7002M_cache_values.db
[INFO] Device name: LimeSDR-USB
[INFO] Reference: 30.72 MHz
[INFO] Init LMS7002M(0)
[INFO] Ver=7, Rev=1, Mask=1
CGEN: Freq=80 MHz, VCO=2.56 GHz, INT=82, FRAC=349525, DIV_OUTCH_CGEN=15
[INFO] LMS7002M calibration values caching Enable
[INFO] SoapyLMS7::setFrequency(Rx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setFrequency(Tx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setAntenna(Rx, 0, LNAL)
[INFO] SoapyLMS7::setAntenna(Tx, 0, BAND1)
[INFO] SoapyLMS7::setGain(Rx, 0, PGA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, LNA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, TIA, 0 dB)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, -50 dB)
[INFO] SoapyLMS7::setSampleRate(Rx, 0, 10 MHz), CGEN=80 MHz, ADC=20 MHz, decim=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=20MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=182, N=7, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 100.4 (steps 58)
[INFO] SoapyLMS7::setSampleRate(Tx, 0, 10 MHz), CGEN=80 MHz, DAC=20 MHz, interp=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=10MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 95.2 (steps 110)
[INFO] SoapyLMS7::setBandwidth(Rx, 0, 30 MHz)
[INFO] Rx Filter calibrated from cache
[INFO] SoapyLMS7::setBandwidth(Tx, 0, 30 MHz)
[INFO] Tx Filter calibrated from cache
[INFO] SoapyLMS7::setFrequency(Rx, 1, BB, 0 MHz)
[INFO] SoapyLMS7::setFrequency(Tx, 1, BB, 0 MHz)
[INFO] SoapyLMS7::setAntenna(Rx, 1, LNAL)
[INFO] SoapyLMS7::setAntenna(Tx, 1, BAND1)
[INFO] SoapyLMS7::setGain(Rx, 1, PGA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 1, LNA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 1, TIA, 0 dB)
[INFO] SoapyLMS7::setGain(Tx, 1, PAD, -50 dB)
[INFO] SoapyLMS7::setSampleRate(Rx, 1, 10 MHz), CGEN=80 MHz, ADC=20 MHz, decim=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=20MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=182, N=7, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 100.4 (steps 58)
[INFO] SoapyLMS7::setSampleRate(Tx, 1, 10 MHz), CGEN=80 MHz, DAC=20 MHz, interp=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=10MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 95.2 (steps 110)
[INFO] SoapyLMS7::setBandwidth(Rx, 1, 30 MHz)
[INFO] Rx Filter calibrated from cache
[INFO] SoapyLMS7::setBandwidth(Tx, 1, 30 MHz)
[INFO] Tx Filter calibrated from cache
[INFO] SoapyLMS7::setSampleRate(Rx, 0, 2 MHz), CGEN=256 MHz, ADC=64 MHz, decim=32
CGEN: Freq=256 MHz, VCO=2.56 GHz, INT=82, FRAC=349525, DIV_OUTCH_CGEN=4
ConnectionSTREAM::ConfigureFPGA_PLL(tx=2MHz, rx=2MHz)
SetFrequency using cache values vco:2, csw:181
[INFO] SoapyLMS7::setFrequency(Rx, 0, RF, 915 MHz)
[WARNING] GetDC_IQ_Interp(915 MHz, ch=0, tx=0): no matches between [914, 916] MHz
[INFO] SoapyLMS7::setFrequency(Rx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setGain(Rx, 0, LNA, 20 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, TIA, 2 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, PGA, 2 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, LNA, 10 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, PGA, 10 dB)
[INFO] SoapyLMS7::setAntenna(Rx, 0, LNAL)
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in sink types: uhd hackrf bladerf soapy redpitaya file 
CGEN: Freq=128 MHz, VCO=2.56 GHz, INT=82, FRAC=349525, DIV_OUTCH_CGEN=9
[INFO] SoapyLMS7::setSampleRate(Tx, 0, 1 MHz), CGEN=128 MHz, DAC=32 MHz, interp=32
ConnectionSTREAM::ConfigureFPGA_PLL(tx=1MHz, rx=2MHz)
SetFrequency using cache values vco:2, csw:182
[INFO] SoapyLMS7::setFrequency(Tx, 0, RF, 915 MHz)
[WARNING] GetDC_IQ_Interp(915 MHz, ch=0, tx=1): no matches between [914, 916] MHz
[INFO] SoapyLMS7::setFrequency(Tx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, 15 dB)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, 15 dB)
[INFO] SoapyLMS7::setAntenna(Tx, 0, BAND1)
'Q' to quit 
Warning popping from TX, samples popped 1314/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 1083/1360
Warning popping from TX, samples popped 0/1360
L 1392640
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Rx: 6.029 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Tx: 0.000 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Rx: 6.023 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360

And that message continually repeats itself. I’ve narrowed it down this file on github in LimeSuite, that is continuously printing that message for a popping of the TX stream. I know some guys working with OpenBTS had a similar problem with this on that setup and a BLE sniffer setup too, but I’m not entirely sure how they fixed it. Is there anyway to mitigate TX popping?

2

That message appears because there are no samples in TX FIFO to transmit. I am not sure how Soapy handles things but generally to stop it from appearing you need to either keep feeding samples to TX stream or stop TX stream.

3

From what I’ve been reading, I think you’re on point. When I multiply or add a DC signal sources with the same sample rate, I know that there are more samples in the FIFO, but it’s still popping. It almost sounds like some of the guys using the USRP had the same problem back in 2013-2014, but they may have resolved it and Nikols Kargas, who made the RFID library, got it to work on the USRP back in 2015.

I suppose it’s time to figure out a gnuradio block to pad in zeros, unless anyone else has any other suggestions or knows of a block that already does this. I’ll also double check that all of the dependencies are fulfilled like @cswiger was suggesting in that OpenBTS post.

4

I followed that github link and in there I followed the fork->network link and there is a fork that is ahead in commits. I have no idea if it helps you. But once in a while I find a fork that works in my favor.

Here’s the repo:

https://github.com/rupumped/Gen2-UHF-RFID-Reader/commit/3f5876ee930bd9950c8db2aa9e3563e1735fa8c7

5

I’ve started to minimize some of the popping issues, but it still occasionally pops by adding the . I also need to figure out why the reader doesn’t pick up the tag right next to it (I checked it with another RFID reader and the tag isn’t dead). It might simply be because it can’t pick up the whisper of the tag with the screaming TX, so I might have to put together a diy directional coupler for a monostatic mode or I’ll need to try more directional antennas so that it’s a more isolated bistatic mode. It might also be one of the rates or another variable inside the reader.

I changed the number of max queries in the reader in global_vars.h to 10000 instead of 1000 and have the following reader code below with a QT time sink:

#!/usr/bin/env python2

from PyQt4 import Qt
from gnuradio import eng_notation
from gnuradio import gr
from gnuradio import qtgui
from gnuradio import blocks
from gnuradio import filter
from gnuradio import digital
from gnuradio.eng_option import eng_option
from gnuradio.filter import firdes
from optparse import OptionParser
from gnuradio import analog
from gnuradio import channels
import osmosdr
import sip
import sys
import time
import rfid

class reader_top_block(gr.top_block, Qt.QWidget):

  def __init__(self):
    gr.top_block.__init__(self)
    Qt.QWidget.__init__(self)
    self.setWindowTitle("Top Block")
    try:
        self.setWindowIcon(Qt.QIcon.fromTheme('gnuradio-grc'))
    except:
        pass
    self.top_scroll_layout = Qt.QVBoxLayout()
    self.setLayout(self.top_scroll_layout)
    self.top_scroll = Qt.QScrollArea()
    self.top_scroll.setFrameStyle(Qt.QFrame.NoFrame)
    self.top_scroll_layout.addWidget(self.top_scroll)
    self.top_scroll.setWidgetResizable(True)
    self.top_widget = Qt.QWidget()
    self.top_scroll.setWidget(self.top_widget)
    self.top_layout = Qt.QVBoxLayout(self.top_widget)
    self.top_grid_layout = Qt.QGridLayout()
    self.top_layout.addLayout(self.top_grid_layout)

    self.settings = Qt.QSettings("GNU Radio", "top_block")
    self.restoreGeometry(self.settings.value("geometry").toByteArray())

    rt = gr.enable_realtime_scheduling()

    ######## Variables #########
    self.adc_rate = 8e6          # ADC rate (2MS/s complex samples)
    self.dac_rate = self.adc_rate/16                # DAC rate
    self.decim = 32                   # Decimation (downsampling factor)
    self.ampl = 0.75                 # Output signal amplitude (signal power vary for different RFX900 cards)
    self.freq = 915e6                # Modulation frequency (can be set between 902-920)
    blf = 100e3
    self.fft = 2**10

    # Each FM0 symbol consists of ADC_RATE/BLF samples (2e6/40e3 = 50 samples)
    # 10 samples per symbol after matched filtering and decimation
    self.num_taps = [1]*int(self.adc_rate/blf/2)  # matched to half symbol period

    self.file_sink_source = blocks.file_sink(gr.sizeof_gr_complex*1, "data/source", False)
    self.file_sink_matched_filter = blocks.file_sink(gr.sizeof_gr_complex*1, "data/matched_filter", False)
    self.file_sink_gate = blocks.file_sink(gr.sizeof_gr_complex*1, "data/gate", False)
    self.file_sink_decoder = blocks.file_sink(gr.sizeof_gr_complex*1, "data/decoder", False)
    self.file_sink_reader = blocks.file_sink(gr.sizeof_gr_complex*1,      "data/reader", False)


    ######## Blocks #########
    self.qtgui_time_sink = qtgui.time_sink_c(
        1024,  # size
        self.adc_rate,  # samp_rate
        "",  # name
        1  # number of inputs
    )
    self.qtgui_time_sink.set_update_time(0.10)
    self.qtgui_time_sink.set_y_axis(-1, 1)

    self.qtgui_time_sink.set_y_label('Amplitude', "")

    self.qtgui_time_sink.enable_tags(-1, True)
    self.qtgui_time_sink.set_trigger_mode(qtgui.TRIG_MODE_AUTO, qtgui.TRIG_SLOPE_POS, 1, 0, 0, "")
    self.qtgui_time_sink.enable_autoscale(False)
    self.qtgui_time_sink.enable_grid(False)
    self.qtgui_time_sink.enable_axis_labels(True)
    self.qtgui_time_sink.enable_control_panel(True)

    if not True:
        self.qtgui_time_sink.disable_legend()

    labels = ['', '', '', '', '',
              '', '', '', '', '']
    widths = [1, 1, 1, 1, 1,
              1, 1, 1, 1, 1]
    colors = ["blue", "red", "green", "black", "cyan",
              "magenta", "yellow", "dark red", "dark green", "blue"]
    styles = [1, 1, 1, 1, 1,
              1, 1, 1, 1, 1]
    markers = [-1, -1, -1, -1, -1,
               -1, -1, -1, -1, -1]
    alphas = [1.0, 1.0, 1.0, 1.0, 1.0,
              1.0, 1.0, 1.0, 1.0, 1.0]

    for i in xrange(2 * 1):
        if len(labels[i]) == 0:
            if (i % 2 == 0):
                self.qtgui_time_sink.set_line_label(i, "Re{{Data {0}}}".format(i / 2))
            else:
                self.qtgui_time_sink.set_line_label(i, "Im{{Data {0}}}".format(i / 2))
        else:
            self.qtgui_time_sink.set_line_label(i, labels[i])
        self.qtgui_time_sink.set_line_width(i, widths[i])
        self.qtgui_time_sink.set_line_color(i, colors[i])
        self.qtgui_time_sink.set_line_style(i, styles[i])
        self.qtgui_time_sink.set_line_marker(i, markers[i])
        self.qtgui_time_sink.set_line_alpha(i, alphas[i])

    self._qtgui_time_sink_win = sip.wrapinstance(self.qtgui_time_sink.pyqwidget(), Qt.QWidget)
    self.top_layout.addWidget(self._qtgui_time_sink_win)

    self.matched_filter = filter.fir_filter_ccc(self.decim, self.num_taps)
    self.gate = rfid.gate(int(self.adc_rate/self.decim))
    self.tag_decoder = rfid.tag_decoder(int(self.adc_rate/self.decim))
    self.reader = rfid.reader(int(self.adc_rate/self.decim), int(self.dac_rate))
    self.amp = blocks.multiply_const_ff(self.ampl)
    self.to_complex = blocks.float_to_complex(1)
    self.blank_signal = analog.sig_source_c(0, analog.GR_CONST_WAVE, 0, 0, 0)
    self.add = blocks.add_vcc(1)

    # Osmocom blocks
    self.u_source = osmosdr.source(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0'  )
    self.u_source.set_sample_rate(self.adc_rate)
    self.u_source.set_center_freq(self.freq, 0)
    self.u_source.set_freq_corr(0, 0)
    self.u_source.set_dc_offset_mode(0, 0)
    self.u_source.set_iq_balance_mode(0, 0)
    self.u_source.set_gain_mode(False, 0)
    self.u_source.set_gain(20, 0)
    self.u_source.set_if_gain(0, 0)
    self.u_source.set_bb_gain(0, 0)
    self.u_source.set_antenna("LNAL", 0)
    self.u_source.set_bandwidth(0, 6000000)

    self.u_sink = osmosdr.sink(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0' )
    self.u_sink.set_sample_rate(self.dac_rate)
    self.u_sink.set_center_freq(self.freq, 0)
    self.u_sink.set_freq_corr(0, 0)
    self.u_sink.set_gain(0, 0)
    self.u_sink.set_if_gain(10, 0)
    self.u_sink.set_bb_gain(5, 0)
    self.u_sink.set_antenna("BAND1", 0)
    self.u_sink.set_bandwidth(0, 1000000)

    ######## Connections #########
    self.connect(self.u_source, self.matched_filter)
    self.connect(self.matched_filter, self.gate)
    self.connect(self.gate, self.tag_decoder)
    self.connect((self.tag_decoder, 0), self.reader)
    self.connect(self.reader, self.amp)
    # self.connect(self.amp, self.to_complex)
    self.connect(self.amp, self.to_complex)
    self.connect(self.to_complex, (self.add, 0))
    self.connect(self.blank_signal, (self.add, 1))
    self.connect((self.add, 0), (self.u_sink, 0))
    self.connect((self.matched_filter, 0), (self.qtgui_time_sink, 0))

    # self.connect(self.gate, self.file_sink_gate)
    self.connect((self.tag_decoder, 1), self.file_sink_decoder) # (Do not comment this line)
    self.connect(self.to_complex, self.file_sink_reader)
    # self.connect(self.matched_filter, self.file_sink_matched_filter)

    def closeEvent(self, event):
        self.settings = Qt.QSettings("GNU Radio", "top_block")
        self.settings.setValue("geometry", self.saveGeometry())
        event.accept()

if __name__ == '__main__':
    from distutils.version import StrictVersion

    if StrictVersion(Qt.qVersion()) >= StrictVersion("4.5.0"):
        style = gr.prefs().get_string('qtgui', 'style', 'raster')
        Qt.QApplication.setGraphicsSystem(style)
    qapp = Qt.QApplication(sys.argv)

    main_block = reader_top_block()
    main_block.start()
    main_block.show()


    def quitting():
        main_block.reader.print_results()
        main_block.stop()
        main_block.wait()


    qapp.connect(qapp, Qt.SIGNAL("aboutToQuit()"), quitting)
    qapp.exec_()

    while (1):
        inp = raw_input("'Q' to quit \n")
        if (inp == "q" or inp == "Q"):
            break
    quitting()

I also received the following output:

linux; GNU C++ version 5.4.0 20160609; Boost_105800; UHD_003.010.001.001-release

gr::log :INFO: gate0 - T1 samples : 62
gr::log :INFO: gate0 - PW samples : 3
gr::log :INFO: gate0 - Samples of Tag bit : 6
gr::log :INFO: gate0 - Size of window : 62
gr::log :INFO: gate0 - Size of window for dc offset estimation : 30
gr::log :INFO: gate0 - Duration of window for dc offset estimation : 120 us
gr::log :INFO: gate0 - Initializing reader state...
gr::log :INFO: tag_decoder0 - Number of samples of Tag bit : 6.25
gr::log :INFO: reader0 - Block initialized
gr::log :INFO: reader0 - Number of samples data 0 : 12
gr::log :INFO: reader0 - Number of samples data 1 : 24
gr::log :INFO: reader0 - Number of samples cw : 125
gr::log :INFO: reader0 - Number of samples delim : 6
gr::log :INFO: reader0 - Number of slots : 1
gr::log :INFO: reader0 - Carrier wave after a query transmission in samples : 1037
gr::log :INFO: reader0 - Carrier wave after ACK transmission in samples : 4087
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy soapy redpitaya 
[INFO] Make connection: 'LimeSDR-USB [USB 3.0] 9060A02592E12'
Estimated reference clock 30.7197 MHz
Selected reference clock 30.720 MHz
[INFO] Device name: LimeSDR-USB
[INFO] Reference: 30.72 MHz
[INFO] Init LMS7002M(0)
LMS7002M values cache at /home/logic/.limesuite/LMS7002M_cache_values.db
[INFO] Ver=7, Rev=1, Mask=1
[INFO] LMS7002M calibration values caching Enable
CGEN: Freq=80 MHz, VCO=2.56 GHz, INT=82, FRAC=349525, DIV_OUTCH_CGEN=15
[INFO] SoapyLMS7::setFrequency(Rx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setFrequency(Tx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setAntenna(Rx, 0, LNAL)
[INFO] SoapyLMS7::setAntenna(Tx, 0, BAND1)
[INFO] SoapyLMS7::setGain(Rx, 0, PGA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, LNA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, TIA, 0 dB)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, -50 dB)
[INFO] SoapyLMS7::setSampleRate(Rx, 0, 10 MHz), CGEN=80 MHz, ADC=20 MHz, decim=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=20MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=182, N=7, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 100.4 (steps 58)
[INFO] SoapyLMS7::setSampleRate(Tx, 0, 10 MHz), CGEN=80 MHz, DAC=20 MHz, interp=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=10MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 95.2 (steps 110)
[INFO] SoapyLMS7::setBandwidth(Rx, 0, 30 MHz)
[INFO] Rx Filter calibrated from cache
[INFO] SoapyLMS7::setBandwidth(Tx, 0, 30 MHz)
[INFO] Tx Filter calibrated from cache
[INFO] SoapyLMS7::setFrequency(Rx, 1, BB, 0 MHz)
[INFO] SoapyLMS7::setFrequency(Tx, 1, BB, 0 MHz)
[INFO] SoapyLMS7::setAntenna(Rx, 1, LNAL)
[INFO] SoapyLMS7::setAntenna(Tx, 1, BAND1)
[INFO] SoapyLMS7::setGain(Rx, 1, PGA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 1, LNA, 0 dB)
[INFO] SoapyLMS7::setGain(Rx, 1, TIA, 0 dB)
[INFO] SoapyLMS7::setGain(Tx, 1, PAD, -50 dB)
[INFO] SoapyLMS7::setSampleRate(Rx, 1, 10 MHz), CGEN=80 MHz, ADC=20 MHz, decim=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=20MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=182, N=7, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 100.4 (steps 58)
[INFO] SoapyLMS7::setSampleRate(Tx, 1, 10 MHz), CGEN=80 MHz, DAC=20 MHz, interp=2
ConnectionSTREAM::ConfigureFPGA_PLL(tx=10MHz, rx=10MHz)
----- FPGA PLL #1 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 114.2 (steps 132)
----- FPGA PLL #0 CONFIG -----
M=156, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 95.2 (steps 110)
[INFO] SoapyLMS7::setBandwidth(Rx, 1, 30 MHz)
[INFO] Rx Filter calibrated from cache
[INFO] SoapyLMS7::setBandwidth(Tx, 1, 30 MHz)
[INFO] Tx Filter calibrated from cache
[INFO] SoapyLMS7::setSampleRate(Rx, 0, 8 MHz), CGEN=512 MHz, ADC=128 MHz, decim=16
CGEN: Freq=512 MHz, VCO=2.048 GHz, INT=65, FRAC=699050, DIV_OUTCH_CGEN=1
ConnectionSTREAM::ConfigureFPGA_PLL(tx=8MHz, rx=8MHz)
----- FPGA PLL #1 CONFIG -----
M=195, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 109.4 (steps 158)
----- FPGA PLL #0 CONFIG -----
M=195, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 94.2 (steps 136)
[INFO] SoapyLMS7::setFrequency(Rx, 0, RF, 915 MHz)
SetFrequency using cache values vco:2, csw:181
[WARNING] GetDC_IQ_Interp(915 MHz, ch=0, tx=0): no matches between [914, 916] MHz
[INFO] SoapyLMS7::setFrequency(Rx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setGain(Rx, 0, LNA, 20 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, TIA, 2 dB)
[INFO] SoapyLMS7::setGain(Rx, 0, PGA, 2 dB)
[INFO] SoapyLMS7::setAntenna(Rx, 0, LNAL)
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in sink types: uhd hackrf bladerf soapy redpitaya file 
[INFO] SoapyLMS7::setSampleRate(Tx, 0, 0.5 MHz), CGEN=64 MHz, DAC=16 MHz, interp=32
CGEN: Freq=64 MHz, VCO=2.432 GHz, INT=78, FRAC=174761, DIV_OUTCH_CGEN=18
ConnectionSTREAM::ConfigureFPGA_PLL(tx=0.5MHz, rx=8MHz)
----- FPGA PLL #1 CONFIG -----
M=195, N=3, Fvco=1040.000 MHz
Configured phase: 0.0 (steps 0)
Configured phase: 109.4 (steps 158)
[INFO] SoapyLMS7::setFrequency(Tx, 0, RF, 915 MHz)
SetFrequency using cache values vco:2, csw:182
[WARNING] GetDC_IQ_Interp(915 MHz, ch=0, tx=1): no matches between [914, 916] MHz
[INFO] SoapyLMS7::setFrequency(Tx, 0, BB, 0 MHz)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, 10 dB)
[INFO] SoapyLMS7::setGain(Tx, 0, PAD, 5 dB)
[INFO] SoapyLMS7::setAntenna(Tx, 0, BAND1)
Warning popping from TX, samples popped 162/1360
L 1392640
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 483/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 949/1360
Tx: 0.177 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 695/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.063 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 1255/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.093 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.224 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 1344/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.058 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.500 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.084 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.508 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.503 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.519 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 1044/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Tx: 1.133 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.516 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.507 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.093 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 695/1360
Warning popping from TX, samples popped 0/1360
Tx: 1.221 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.494 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.513 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.506 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.093 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.481 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 670/1360
Warning popping from TX, samples popped 0/1360
Tx: 1.199 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.494 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.504 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 402/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.220 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.507 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.487 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 994/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 1179/1360
Warning popping from TX, samples popped 0/1360
Tx: 0.934 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.093 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.511 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 855/1360
Warning popping from TX, samples popped 0/1360
Tx: 1.208 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.508 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.506 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.510 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.503 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Tx: 1.500 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 828/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 981/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 552/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Tx: 0.522 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 540/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 540/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Rx: 24.093 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 552/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Tx: 0.080 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
Warning popping from TX, samples popped 528/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 528/1360
Rx: 24.117 MB/s, Fs: 0.000 MHz, overrun: 0, loss: 0 
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 0/1360
Warning popping from TX, samples popped 552/1360
Warning popping from TX, samples popped 0/1360

 --------------------------
| Number of queries/queryreps sent : 2388
| Current Inventory round : 2393
 --------------------------
| Correctly decoded EPC : 0
| Number of unique tags : 0
 --------------------------
Warning popping from TX, samples popped 0/1360
Tx: 0.087 MB/s, Fs: 0.000 MHz, failures: 0, ts:0
'Q' to quit 
q

 --------------------------
| Number of queries/queryreps sent : 2388
| Current Inventory round : 2393
 --------------------------
| Correctly decoded EPC : 0
| Number of unique tags : 0
 --------------------------

 --------------------------
| Number of queries/queryreps sent : 2388
| Current Inventory round : 2393
 --------------------------
| Correctly decoded EPC : 0
| Number of unique tags : 0
 --------------------------

I’m honestly glad the TX actually outputs the approximately correct sample rate (1.5 MB/s which is 1/16 of 24 MB/s). Here’s the output from the filter that is connected to the receiver:per of the tag with the screaming TX, so I might have to put together a diy directional coupler for a monostatic mode or I’ll need to try more directional antennas so that it’s a more isolated bistatic mode.

I changed the number of max queries in the reader in global_vars.h to 10000 instead of 1000 and have the following reader code below with a QT time sink, but it still is finicky if I change any of the variables, where it won’t transmit at all:

5.png1315×711 115 KB

6

After messing with another RFID library that also claims that it works on the bladeRF, I had more popping issues. However when I pulled LimeSuite from the osmotrx fork (from @IgnasJ)and built it, I’m not seeing the popping error. I’m still not able to read the RFID tag completely (although it is able to acknowledge the tag sometimes) with the following file:

#!/usr/bin/env python
# Developed by: Michael Buettner (buettner@cs.washington.edu)
# Modified by: Bruno Espinoza (bruno.espinozaamaya@uqconnect.edu.au)
# Modified for LimeSDR by: Jordan Treiwtt (jot437@utulsa.edu)

from gnuradio import gr, gru
from PyQt4 import Qt
from gnuradio import eng_notation
from gnuradio import qtgui
from gnuradio import analog, blocks, digital, filter
from gnuradio.eng_option import eng_option
from string import split
from string import strip
from string import atoi
import time
import os
import math
import sys
import rfid
import optparse
import osmosdr
import sip

# parser for frequency and other options
parser = optparse.OptionParser();
parser.add_option('--f', action="store", dest="center_freq", default="910e6", help="Center Frequency", type="float");
parser.add_option('--g', action="store", dest="rx_gain", default="20", help="RX Gain", type="float");
parser.add_option('--l', action="store", dest="log_file", default="log_out.log", help="Log file name");
parser.add_option('--d', action="store", dest="dump_file", default="none", help="[none|matched|full]");
parser.add_option('--s', action="store", dest="device", default="uhd", help="[uhd|bladerf]");
parser.add_option('--q', action="store", dest="q_value", default="0", help="Q value from 0 to 8");
parser.add_option('--m', action="store", dest="modul_type", default="1",
                  help="Modulation Type from 0 to 3 -> 0: FM Encoding, 1: Miller M=2, 2: Miller M=4, 3: Miller M=8");
parser.add_option('--c', action="store", dest="cycles_num", default="5", help="Number of Reader Cycles (def. 5)");
parser.add_option('--r', action="store", dest="round_num", default="10", help="Number of Rounds per Cycle (def. 10)");

options, args = parser.parse_args()

log_file = open(options.log_file, "a")
dump_type = options.dump_file
mtype = int(options.modul_type)
qval = int(options.q_value)
n_cycle = int(options.cycles_num)
n_round = int(options.round_num)

if dump_type == "none":
    print "* Alert: Skipping dumping of the rx block..."
elif dump_type == "full":
    print "** Using a full dump of the RX block!!"
elif dump_type == "matched":
    print "** Using dump of the match_filter block!!"
else:
    print "Unknown dump_type flag!! Set to 'none'"
    dump_type = 'none'

if options.device == "uhd":
    print "Using USRP devices..."
else:
    print "Using bladeRF device..."

modul_msg = ["FM0", "Miller M=2", "Miller M=4", "Miller M=8"];

if mtype > 3 or mtype < 0:
    mtype = 1;

if (qval > 8 or qval < 0):
    qval = 0

slots = pow(2, qval);

print "* Using", modul_msg[mtype], "modulation for tags..."
print "* Q Value of", str(qval), "so", str(slots), "slots assigned for tags..."
print "* Reader using", str(n_cycle), "cycles with", str(n_round), "rounds per cycle..."


class my_top_block(gr.top_block, Qt.QWidget):
    def __init__(self):
        gr.top_block.__init__(self)
        Qt.QWidget.__init__(self)
        self.setWindowTitle("Top Block")
        try:
            self.setWindowIcon(Qt.QIcon.fromTheme('gnuradio-grc'))
        except:
            pass
        self.top_scroll_layout = Qt.QVBoxLayout()
        self.setLayout(self.top_scroll_layout)
        self.top_scroll = Qt.QScrollArea()
        self.top_scroll.setFrameStyle(Qt.QFrame.NoFrame)
        self.top_scroll_layout.addWidget(self.top_scroll)
        self.top_scroll.setWidgetResizable(True)
        self.top_widget = Qt.QWidget()
        self.top_scroll.setWidget(self.top_widget)
        self.top_layout = Qt.QVBoxLayout(self.top_widget)
        self.top_grid_layout = Qt.QGridLayout()
        self.top_layout.addLayout(self.top_grid_layout)

        self.settings = Qt.QSettings("GNU Radio", "top_block")
        self.restoreGeometry(self.settings.value("geometry").toByteArray())

        # Constants

        amplitude = 5000
        sw_dec = 5  # For reduce the sample rate after the filtering. (4MS / 5 = 800 KS/s)
        samp_rate = 4e6  # corresponds to dec_rate 16. (64M/16)
        tx_sample = .5e6

        # Filter mathced to 1/4 of 40 KHz tag cycle.
        # 40 KHz = 100 samples, so 1/4 is 25 samples.
        # num_taps = int(64000 / ( (dec_rate * 4) * 40 )) #Filter matched to 1/4 of the 40 kHz tag cycle
        num_taps = 25
        taps = [complex(1, 1)] * num_taps

        # Blocks

        matched_filt = filter.fir_filter_ccc(sw_dec, taps);

        agc = analog.agc2_cc(0.3, 1e-3, 1, 1)
        agc.set_max_gain(100)

        to_mag = blocks.complex_to_mag()
        center = rfid.center_ff(10)

        omega = 5
        mu = 0.25
        gain_mu = 0.25
        gain_omega = .25 * gain_mu * gain_mu
        omega_relative_limit = .05

        # clock recovery
        mm = digital.clock_recovery_mm_ff(omega, gain_omega, mu, gain_mu, omega_relative_limit)

        mtype = int(options.modul_type)
        qval = int(options.q_value)

        if (mtype > 3 or mtype < 0):
            mtype = 1  # Miller M=2 by default

        # qval = int(options.q_value)
        if qval > 8 or qval < 0:
            qval = 0;

        n_cycle = int(options.cycles_num)
        n_round = int(options.round_num)

        self.reader = rfid.reader_f(int(tx_sample), mtype, qval, n_cycle, n_round)
        tag_decoder = rfid.tag_decoder_f()

        # The parameters for command_gate_cc are:
        # - PW: 12 us. (Negative part of the PIE pulses)
        # - T1: 250 us (Maximium timeout for the tag to reply).
        # - Sample Rate. (800 KS/s after the matched filter)
        command_gate = rfid.command_gate_cc(12, 250, int(800e3))  # 800 KS/s.
        dc_block = filter.dc_blocker_cc(64, True)

        to_complex = blocks.float_to_complex()
        amp = blocks.multiply_const_ff(amplitude)
        # TX
        freq = options.center_freq  # 915e6
        rx_gain = options.rx_gain  # 20
        if (options.device == "uhd"):
            tx = osmosdr.sink("uhd,type=usrp1")
            tx.set_gain(0, 'DAC-pga')  # range -20 to 0.
            tx.set_antenna('TX/RX')
        else:
            # LimeSDR
            tx = osmosdr.sink(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0')
            tx.set_gain(30, 0)
            tx.set_if_gain(10, 0)
            tx.set_bb_gain(10, 0)
            tx.set_antenna("BAND1", 0)
            tx.set_bandwidth(0, 1000000)

            # Settings for Backscatter = VGA1 = -4 / VGA2 = 20

        tx.set_sample_rate(tx_sample)
        tx.set_center_freq(freq)

        if not tx:
            print "Couldn't set tx freq"

        # End TX

        # RX
        if (options.device == "uhd"):
            rx = osmosdr.source("uhd,type=usrp1")
            rx.set_gain(20, 'PGA0')
            rx.set_gain(15, 'ADC-pga')
            rx.set_antenna('RX2')
        else:
            # LimeSDR
            rx = osmosdr.source(args="numchan=" + str(1) + " " + 'driver=lime,soapy=0')
            rx.set_gain_mode(False, 0)
            rx.set_gain(20, 0)
            rx.set_if_gain(10, 0)
            rx.set_bb_gain(10, 0)
            rx.set_antenna("LNAL", 0)
            rx.set_bandwidth(0, 6000000)

        rx.set_sample_rate(samp_rate)
        rx.set_center_freq(freq)
        # rx.set_iq_balance_mode(0, 0)
        # rx.set_dc_offset_mode(0, 0)

        if not rx:
            print "Couldn't set rx freq"

        # End RX
        command_gate.set_ctrl_out(self.reader.ctrl_q())
        tag_decoder.set_ctrl_out(self.reader.ctrl_q())

        # QT setup

        self.qtgui_time_sink = qtgui.time_sink_c(
            1024,  # size
            samp_rate,  # samp_rate
            "",  # name
            1  # number of inputs
        )
        self.qtgui_time_sink.set_update_time(0.10)
        self.qtgui_time_sink.set_y_axis(-5, 5)

        self.qtgui_time_sink.set_y_label('Amplitude', "")

        self.qtgui_time_sink.enable_tags(-1, True)
        self.qtgui_time_sink.set_trigger_mode(qtgui.TRIG_MODE_AUTO, qtgui.TRIG_SLOPE_POS, 1, 0, 0, "")
        self.qtgui_time_sink.enable_autoscale(False)
        self.qtgui_time_sink.enable_grid(False)
        self.qtgui_time_sink.enable_axis_labels(True)
        self.qtgui_time_sink.enable_control_panel(True)

        if not True:
            self.qtgui_time_sink.disable_legend()

        labels = ['', '', '', '', '',
                  '', '', '', '', '']
        widths = [1, 1, 1, 1, 1,
                  1, 1, 1, 1, 1]
        colors = ["blue", "red", "green", "black", "cyan",
                  "magenta", "yellow", "dark red", "dark green", "blue"]
        styles = [1, 1, 1, 1, 1,
                  1, 1, 1, 1, 1]
        markers = [-1, -1, -1, -1, -1,
                   -1, -1, -1, -1, -1]
        alphas = [1.0, 1.0, 1.0, 1.0, 1.0,
                  1.0, 1.0, 1.0, 1.0, 1.0]

        for i in xrange(2 * 1):
            if len(labels[i]) == 0:
                if (i % 2 == 0):
                    self.qtgui_time_sink.set_line_label(i, "Re{{Data {0}}}".format(i / 2))
                else:
                    self.qtgui_time_sink.set_line_label(i, "Im{{Data {0}}}".format(i / 2))
            else:
                self.qtgui_time_sink.set_line_label(i, labels[i])
            self.qtgui_time_sink.set_line_width(i, widths[i])
            self.qtgui_time_sink.set_line_color(i, colors[i])
            self.qtgui_time_sink.set_line_style(i, styles[i])
            self.qtgui_time_sink.set_line_marker(i, markers[i])
            self.qtgui_time_sink.set_line_alpha(i, alphas[i])

        self._qtgui_time_sink_win = sip.wrapinstance(self.qtgui_time_sink.pyqwidget(), Qt.QWidget)
        self.top_layout.addWidget(self._qtgui_time_sink_win)


        #########Build Graph
        self.connect(rx, dc_block)
        self.connect(dc_block, matched_filt)
        self.connect(matched_filt, self.qtgui_time_sink)
        self.connect(matched_filt, command_gate)
        self.connect(command_gate, agc)
        self.connect(agc, to_mag)
        self.connect(to_mag, center, mm, tag_decoder)
        self.connect(tag_decoder, self.reader, amp, to_complex, tx)
        #################

        # Output dumps for debug

        # self.connect(to_complex, f_txout);
        if dump_type == "matched":
            f_rxout = blocks.file_sink(gr.sizeof_gr_complex, 'f_rxout.out');
            self.connect(matched_filt, f_rxout)
            # f_rxout = blocks.file_sink(gr.sizeof_float, 'f_rxout.out');
            # self.connect(mm, f_rxout)

        if dump_type == "full":
            f_rxout = blocks.file_sink(gr.sizeof_gr_complex, 'f_rxout.out');
            self.connect(rx, f_rxout)

    def closeEvent(self, event):
        self.settings = Qt.QSettings("GNU Radio", "top_block")
        self.settings.setValue("geometry", self.saveGeometry())
        event.accept()


def main():
    from distutils.version import StrictVersion

    if StrictVersion(Qt.qVersion()) >= StrictVersion("4.5.0"):
        style = gr.prefs().get_string('qtgui', 'style', 'raster')
        Qt.QApplication.setGraphicsSystem(style)
    qapp = Qt.QApplication(sys.argv)

    tb = my_top_block()

    tb.start()
    tb.show()

    qapp.exec_()

    while 1:

        c = raw_input("'Q' to quit. L to get log.\n")
        if c == "q":
            break

        if c == "L" or c == "l":
            log_file.write("T,CMD,ERROR,BITS,SNR\n")
            log = tb.reader.get_log()
            print "Log has %s Entries" % (str(log.count()))
            i = log.count();

            for k in range(0, i):
                msg = log.delete_head_nowait()
                print_log_msg(msg, log_file)

    tb.stop()


def print_log_msg(msg, log_file):
    LOG_START_CYCLE, LOG_QUERY, LOG_ACK, LOG_QREP, LOG_NAK, LOG_REQ_RN, LOG_READ, LOG_RN16, LOG_EPC, LOG_HANDLE, LOG_DATA, LOG_EMPTY, LOG_COLLISION, LOG_OKAY, LOG_ERROR = range(
        15)

    fRed = chr(27) + '[31m'
    fBlue = chr(27) + '[34m'
    fReset = chr(27) + '[0m'

    if msg.type() == LOG_START_CYCLE:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t Started Cycle" % (fields[-1])
        log_file.write(fields[-1] + ",START_CYCLE,0,0,0\n");

    if msg.type() == LOG_QUERY:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t Query" % (fields[-1])
        log_file.write(fields[-1] + ",QUERY,0,0,0\n");

    if msg.type() == LOG_QREP:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t QRep" % (fields[-1])
        log_file.write(fields[-1] + ",QREP,0,0,0\n");

    if msg.type() == LOG_ACK:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t ACK" % (fields[-1])
        log_file.write(fields[-1] + ",ACK,0,0,0\n");

    if msg.type() == LOG_NAK:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t NAK" % (fields[-1])
        log_file.write(fields[-1] + ",NAK,0,0,0\n");

    if msg.type() == LOG_RN16:
        fields = split(strip(msg.to_string()), " ")
        rn16 = fields[0].split(",")[0]
        snr = strip(fields[0].split(",")[1])
        tmp = int(rn16, 2)

        if msg.arg2() == LOG_ERROR:

            print "%s\t    %s RN16 w/ Error: %04X%s" % (fields[-1], fRed, tmp, fReset)
            log_file.write(fields[-1] + ",RN16,1," + "%04X" % tmp + "," + snr + "\n");
        else:
            print "%s\t    %s RN16: %04X%s" % (fields[-1], fBlue, tmp, fReset)
            log_file.write(fields[-1] + ",RN16,0," + "%04X" % tmp + "," + snr + "\n");

    if msg.type() == LOG_EPC:
        fields = split(strip(msg.to_string()), " ")
        epc = fields[0].split(",")[0]
        snr = strip(fields[0].split(",")[1])
        epc = epc[16:112]

        tmp = int(epc, 2)
        if msg.arg2() == LOG_ERROR:
            print "%s\t    %s EPC w/ Error: %024X%s" % (fields[-1], fRed, tmp, fReset)
            log_file.write(fields[-1] + ",EPC,1," + "%024X" % tmp + "," + snr + "\n");
        else:
            print "%s\t    %s EPC: %024X%s" % (fields[-1], fBlue, tmp, fReset)
            log_file.write(fields[-1] + ",EPC,0," + "%024X" % tmp + "," + snr + "\n");

    if msg.type() == LOG_EMPTY:
        fields = split(strip(msg.to_string()), " ")
        snr = strip(fields[0])
        print "%s\t    - Empty Slot - " % (fields[-1])
        log_file.write(fields[-1] + ",EMPTY,0,0," + snr + "\n");

    if msg.type() == LOG_COLLISION:
        fields = split(strip(msg.to_string()), " ")
        print "%s\t    - Collision - " % (fields[-1])
        log_file.write(fields[-1] + ",COLLISION,0,0,0\n");


if __name__ == '__main__':
    main()

With the following output:

logic@logic-ThinkPad-X260:~/PycharmProjects/LimeReader$ python LimeReader2.py --s akdf --r 100 --c 100 --m 8
linux; GNU C++ version 5.4.0 20160609; Boost_105800; UHD_003.010.001.001-release

* Alert: Skipping dumping of the rx block...
Using bladeRF device...
* Using Miller M=2 modulation for tags...
* Q Value of 0 so 1 slots assigned for tags...
* Reader using 100 cycles with 100 rounds per cycle...
us Per Sample: 1.250000 Num samples per pulse:9 T1:200
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in sink types: uhd hackrf bladerf soapy redpitaya file 
[INFO] Make connection: 'LimeSDR-USB [USB 2.0] 9060A02592E12'
[INFO] Estimated reference clock 30.7197 MHz
[INFO] Selected reference clock 30.720 MHz
[INFO] Device name: LimeSDR-USB
[INFO] Reference: 30.72 MHz
[INFO] Init LMS7002M(0)
[INFO] LMS7002M cache /home/logic/.limesuite/LMS7002M_cache_values.db
[INFO] Ver=7, Rev=1, Mask=1
[INFO] LMS7002M calibration values caching Enable
[INFO] Rx Filter calibrated from cache
[INFO] Tx Filter calibrated from cache
[INFO] Rx Filter calibrated from cache
[INFO] Tx Filter calibrated from cache
SetFrequency using cache values vco:2, csw:175
gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.10
built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy soapy redpitaya 
SetFrequency using cache values vco:2, csw:173
############################################################
Tx calibration values found in cache:
   | DC  | GAIN | PHASE
---+-----+------+------
I: | 626 | 1974 | -17
Q: | 114 | 2047 |
############################################################
############################################################
Rx calibration using RSSI INTERNAL ON BOARD loopback
Rx ch.A @  910 MHz, BW: 30 MHz, RF input: LNAL, PGA: 22, LNA: 4, TIA: 1
Rx calibration: using cached values
Rx calibration values found in cache:
   | DC  | GAIN | PHASE
---+-----+------+------
I: |   0 | 2047 | 0
Q: |   0 | 2047 |
############################################################
Timer fired starting cycle
Timer fired starting cycle
[INFO] L
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 10
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
[INFO] L
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 20
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 30
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 40
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 50
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Starting cycle 60
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
Timer fired starting cycle
'Q' to quit. L to get log.
Timer fired starting cycle
Starting cycle 70
Timer fired starting cycle
Timer fired starting cycle
lTimer fired starting cycle

Log has 479 Entries
66804.589	 Started Cycle
66804.589	 Query
66804.636	 Started Cycle
66804.636	 Query
66805.137	 Started Cycle
66805.137	 Query
66805.637	 Started Cycle
66805.637	 Query
66806.136	 Started Cycle
66806.136	 Query
66806.637	 Started Cycle
66806.637	 Query
66807.136	 Started Cycle
66807.136	 Query
66807.637	 Started Cycle
66807.637	 Query
66808.137	 Started Cycle
66808.137	 Query
66808.576	    - Empty Slot - 
66808.576	 Query
66808.636	 Started Cycle
66808.636	 Query
66808.837	    - Empty Slot - 
66808.837	 Query
66809.137	 Started Cycle
66809.137	 Query
66809.152	    - Empty Slot - 
66809.152	 Query
66809.442	    - Empty Slot - 
66809.442	 Query
66809.619	    - Empty Slot - 
66809.619	 Query
66809.637	 Started Cycle
66809.637	 Query
66810.136	 Started Cycle
66810.136	 Query
66810.637	 Started Cycle
66810.637	 Query
66811.136	 Started Cycle
66811.136	 Query
66811.618	    - Empty Slot - 
66811.618	 Query
66811.636	 Started Cycle
66811.636	 Query
66811.799	    - Empty Slot - 
66811.799	 Query
66811.879	    - Empty Slot - 
66811.879	 Query
66811.883	     RN16: E856
66811.883	 ACK
66812.137	 Started Cycle
66812.137	 Query
66812.553	    - Empty Slot - 
66812.553	 Query
66812.636	 Started Cycle
66812.636	 Query
66812.667	    - Empty Slot - 
66812.667	 Query
66812.784	    - Empty Slot - 
66812.785	 Query
66812.838	    - Empty Slot - 
66812.838	 Query
66812.935	    - Empty Slot - 
66812.935	 Query
66812.963	    - Empty Slot - 
66812.963	 Query
66813.067	    - Empty Slot - 
66813.067	 Query
66813.136	 Started Cycle
66813.136	 Query
66813.144	    - Empty Slot - 
66813.144	 Query
66813.250	    - Empty Slot - 
66813.250	 Query
66813.262	    - Empty Slot - 
66813.262	 Query
66813.393	    - Empty Slot - 
66813.393	 Query
66813.420	    - Empty Slot - 
66813.420	 Query
66813.506	    - Empty Slot - 
66813.506	 Query
66813.555	    - Empty Slot - 
66813.555	 Query
66813.625	    - Empty Slot - 
66813.625	 Query
66813.637	 Started Cycle
66813.637	 Query
66814.136	 Started Cycle
66814.136	 Query
66814.563	    - Empty Slot - 
66814.563	 Query
66814.577	    - Empty Slot - 
66814.577	 Query
66814.628	    - Empty Slot - 
66814.628	 Query
66814.636	 Started Cycle
66814.636	 Query
66814.681	    - Empty Slot - 
66814.681	 Query
66814.715	    - Empty Slot - 
66814.715	 Query
66814.740	    - Empty Slot - 
66814.740	 Query
66814.804	     RN16 w/ Error: 0980
66814.804	 Query
66814.922	    - Empty Slot - 
66814.922	 Query
66814.941	    - Empty Slot - 
66814.941	 Query
66815.014	    - Empty Slot - 
66815.014	 Query
66815.039	    - Empty Slot - 
66815.039	 Query
66815.137	 Started Cycle
66815.137	 Query
66815.188	    - Empty Slot - 
66815.188	 Query
66815.636	 Started Cycle
66815.636	 Query
66815.720	    - Empty Slot - 
66815.720	 Query
66815.800	    - Empty Slot - 
66815.800	 Query
66815.965	    - Empty Slot - 
66815.965	 Query
66816.137	 Started Cycle
66816.137	 Query
66816.397	    - Empty Slot - 
66816.397	 Query
66816.637	 Started Cycle
66816.637	 Query
66817.136	 Started Cycle
66817.136	 Query
66817.170	    - Empty Slot - 
66817.170	 Query
66817.577	    - Empty Slot - 
66817.577	 Query
66817.636	 Started Cycle
66817.636	 Query
66817.680	    - Empty Slot - 
66817.680	 Query
66817.817	    - Empty Slot - 
66817.817	 Query
66817.937	    - Empty Slot - 
66817.937	 Query
66818.059	    - Empty Slot - 
66818.059	 Query
66818.136	 Started Cycle
66818.136	 Query
66818.297	    - Empty Slot - 
66818.297	 Query
66818.439	    - Empty Slot - 
66818.439	 Query
66818.636	 Started Cycle
66818.636	 Query
66818.651	    - Empty Slot - 
66818.651	 Query
66818.679	    - Empty Slot - 
66818.679	 Query
66819.137	 Started Cycle
66819.137	 Query
66819.637	 Started Cycle
66819.637	 Query
66820.136	 Started Cycle
66820.136	 Query
66820.637	 Started Cycle
66820.637	 Query
66821.136	 Started Cycle
66821.136	 Query
66821.637	 Started Cycle
66821.637	 Query
66821.789	    - Empty Slot - 
66821.789	 Query
66822.138	 Started Cycle
66822.138	 Query
66822.571	    - Empty Slot - 
66822.571	 Query
66822.574	    - Empty Slot - 
66822.574	 Query
66822.636	 Started Cycle
66822.636	 Query
66822.689	    - Empty Slot - 
66822.689	 Query
66822.695	    - Empty Slot - 
66822.695	 Query
66822.701	    - Empty Slot - 
66822.701	 Query
66822.806	    - Empty Slot - 
66822.806	 Query
66822.822	    - Empty Slot - 
66822.822	 Query
66822.830	    - Empty Slot - 
66822.830	 Query
66822.896	    - Empty Slot - 
66822.896	 Query
66822.900	    - Empty Slot - 
66822.900	 Query
66823.039	    - Empty Slot - 
66823.039	 Query
66823.079	    - Empty Slot - 
66823.079	 Query
66823.080	    - Empty Slot - 
66823.080	 Query
66823.089	    - Empty Slot - 
66823.089	 Query
66823.136	 Started Cycle
66823.136	 Query
66823.637	 Started Cycle
66823.637	 Query
66824.137	 Started Cycle
66824.137	 Query
66824.341	    - Empty Slot - 
66824.341	 Query
66824.351	    - Empty Slot - 
66824.351	 Query
66824.364	    - Empty Slot - 
66824.364	 Query
66824.396	    - Empty Slot - 
66824.396	 Query
66824.461	    - Empty Slot - 
66824.461	 Query
66824.476	    - Empty Slot - 
66824.476	 Query
66824.480	    - Empty Slot - 
66824.480	 Query
66824.485	    - Empty Slot - 
66824.486	 Query
66824.627	    - Empty Slot - 
66824.627	 Query
66824.632	    - Empty Slot - 
66824.632	 Query
66824.637	 Started Cycle
66824.637	 Query
66824.652	    - Empty Slot - 
66824.652	 Query
66824.741	    - Empty Slot - 
66824.741	 Query
66824.747	    - Empty Slot - 
66824.747	 Query
66824.756	    - Empty Slot - 
66824.756	 Query
66825.137	 Started Cycle
66825.137	 Query
66825.151	    - Empty Slot - 
66825.151	 Query
66825.636	 Started Cycle
66825.636	 Query
66825.653	    - Empty Slot - 
66825.653	 Query
66825.895	    - Empty Slot - 
66825.895	 Query
66825.931	    - Empty Slot - 
66825.931	 Query
66826.040	    - Empty Slot - 
66826.040	 Query
66826.139	 Started Cycle
66826.139	 Query
66826.139	    - Empty Slot - 
66826.139	 Query
66826.179	    - Empty Slot - 
66826.179	 Query
66826.400	    - Empty Slot - 
66826.400	 Query
66826.523	    - Empty Slot - 
66826.523	 Query
66826.636	 Started Cycle
66826.636	 Query
66826.766	    - Empty Slot - 
66826.766	 Query
66826.826	    - Empty Slot - 
66826.826	 Query
66826.846	    - Empty Slot - 
66826.846	 Query
66827.136	 Started Cycle
66827.136	 Query
66827.211	    - Empty Slot - 
66827.211	 Query
66827.251	    - Empty Slot - 
66827.251	 Query
66827.255	    - Empty Slot - 
66827.255	 Query
66827.258	    - Empty Slot - 
66827.258	 Query
66827.474	     RN16: D0DC
66827.474	 ACK
66827.492	     EPC w/ Error: A030B048433200C606019D46
66827.492	 NAK
66827.492	 Query
66827.503	    - Empty Slot - 
66827.503	 Query
66827.507	    - Empty Slot - 
66827.507	 Query
66827.540	    - Empty Slot - 
66827.540	 Query
66827.579	     RN16 w/ Error: D0F0
66827.579	 Query
'Q' to quit. L to get log.

Again I probably need to add filters to the TX, but at least it’s able to ACK the RN.

7

Hi tungstenlightbulb,

I’m currently also trying to get LimeSDR working with RFID through GNU Radio; just wondering if you had made any further progress/observations since the above discussion? I’m going to try out some of what you’ve tried above tomorrow.

8

Sorry I haven’t gotten back to you. I haven’t tried the library in months and the last time I used it I was only receiving partial reads as detailed in that latest post. I should probably try it again to see if any of the newer firmware updates fixed anything, but I was talking to another more experienced SDR programmer and he was saying that this type of issue could commonly be fixed if you add a delay right after the source in order to fix some of the buffering problems. I have yet to try that, so I can’t really say.

Have you had any success so far with your current configuration?

9

So the stage I’m at currently is that I can get the LimeSDR to transmit the query, and the tag successfully responds with the RN16. After that however, there is a long delay (~7ms) before the LimeSDR attempts to reply with an ACK, and so the tag stops listening (at the 40 kHz BLF we’re using the reader needs to start responding within 500 us), so the communication stops there. See the figure below.

I’ve been using the same Gen 2 UFH RFID library that you were trying originally, but I never seemed to get the TX popping issues that you mentioned above. I also used the same code that you originally posted (with some slight modifications to put back in the other file sink blocks and change the file locations slightly).

I don’t seem to get nearly as much output on my screen as you do; this is all I get when I run the script:

linux; GNU C++ version 5.4.0 20160609; Boost_105800; UHD_003.010.002.000-3-g122bfae1

gr-osmosdr v0.1.4-98-gc653754d (0.1.5git) gnuradio 3.7.11.1
built-in source types: file fcd rtl rtl_tcp uhd hackrf bladerf rfspace airspy soapy redpitaya 
[INFO] Make connection: 'LimeSDR-USB [USB 3.0] 9062000C41E13'
[INFO] Reference clock 30.720 MHz
[INFO] Device name: LimeSDR-USB
[INFO] Reference: 30.72 MHz
[INFO] Init LMS7002M(0)
[INFO] Ver=7, Rev=1, Mask=1
[INFO] LMS7002M calibration values caching Disable
gr-osmosdr v0.1.4-98-gc653754d (0.1.5git) gnuradio 3.7.11.1
built-in sink types: uhd hackrf bladerf soapy redpitaya file 
'Q' to quit 
[INFO] L
q

 --------------------------
| Number of queries/queryreps sent : 8
| Current Inventory round : 9
 --------------------------
| Correctly decoded EPC : 0
| Number of unique tags : 0
 --------------------------

Is there some kind of logging parameter that I need to enable somewhere to get the more verbose output? The output pauses at ‘[INFO] L’ until either I press q or it tries 1000 attempts (as defined in global_vars.h), which takes about 20 minutes.

7_ms_delay_pic
7_ms_delay_pic.png755×309 4.2 KB

With regards to the latency issue, I suspect it’s to do with the USB transfer packet size - see the post I just made here for more specific details.

I also seem to get a weird unwanted sawtooth waveform in the RX, the frequency of which is affected by the sampling rate; it this something you’ve experienced? More detailed post is here ; the picture shown above is taken in the first 50ms or so of the signal where the sawtooth hasn’t started up yet.

Thanks,

DasSidG