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Replay captured IQ samples ​

Both HackRF and RTL-SDR have command line tools to capture IQ samples. OpenStint can replay these samples. This is useful for testing and debugging.

When doing the capture, take care:

  • openstint_rtlsdr processes 2 samples per symbol.
  • openstint_hackrf processes 4 samples per symbol by default; but it's settable to 2, 4 or 8.

rtl_sdr ​

rtl_sdr -f 5000000 -s 2500000 -g 20 -n 12500000 capture.iq
openstint_rtlsdr -c capture.iq
  • -f 5000000: center frequency 5 MHz
  • -s 2500000: sample rate 2.5 MSPS
  • -g 20: built-in amplifier gains
  • -n 12500000: record 5 seconds worth of data (5 s * 2.5 MSPS = 12500000 samples)

hackrf_transfer ​

hackrf_transfer -r capture.iq -f 5000000 -s 5000000 -l 20 -g 20 -n 25000000
openstint_hackrf -c capture.iq
  • -f 5000000: center frequency 5 MHz
  • -s 5000000: sample rate 5 MSPS
  • -l 20, -g 20: built-in LNA and VGA gains
  • -n 25000000: record 5 seconds worth of data (5 s * 5 MSPS = 25000000 samples)

Note:

  • for SAMPLES_PER_SYMBOL=2, use -s 2500000 -n 12500000
  • for SAMPLES_PER_SYMBOL=4, use -s 5000000 -n 25000000
  • for SAMPLES_PER_SYMBOL=8, use -s 10000000 -n 50000000