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README_improvements.md

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improvements, compared to the osmocom sources

versions

comparing osmocom's git git://git.osmocom.org/rtl-sdr.git dated from 2020-08-19 against librtlsdr's development branch (initially same date, but updated 2020-10-04)

"Driver" Library Features

  • added support for special USB (vendor) VID 0x1209 (product) PID 0x2832: "Generic RTL2832U":

  • added support for using RTLSDR-Dongle from remote - see rtl_rpcd and README.rtlsdr_rpc

  • support for all GPIO pins of RTL2832 through API and rtl_biast

  • improvements for R820T/2 tuner also see https://codingspirit.de/librtlsdr-driver.pdf several features from https://github.com/old-dab/rtlsdr/

    • added better bandwidth support
      • added smaller bandwidths, improving selectivity: 290, 375, 420, 470, 600, 860, 950, 1100, 1200, 1300, 1500, 1600, 1750, 1800, 1950, 2200, 3000, 5000 kHz. These are coarse measured values .. which might get adjusted in future.
      • bandwidth filters utilize tuner's low- and highpass filters at IF
    • added spectrum flipping (inside tuner) - and back in RTL2832
      • the band edges (low/high-pass) have different steepness; the steeper edge can be selected with the mixer sideband (rtlsdr_set_tuner_sideband()), to achieve better attenuation depending on signal scenario
    • added (automatic) control over VGA (variable gain amplifier)
      • VGA gain (besides LNA and Mixer) can be utilized and set to automatic, letting it controlled from RTL2832U. Having all automatic (AGC) including activation of digital AGC in RTL2832 (rtlsdr_set_agc_mode()), oversteering effects got reduced (a lot).
      • total gain range now up to 100 dB
    • deactivated "Filter extension under weak signal" for a stable filter characteristic
    • added shifting of IF-center, to receive away from DC. see rtlsdr_set_tuner_band_center()

  • harmonic reception for R820T/2 tuner:

    • allow reception for frequencies above ~ 1.76 GHz
    • tested in lab conditions up to 6.0 GHz
    • 5th harmonic is used automatically by default when direct reception is not possible (when tuner-PLL doesn't lock)
    • 3rd harmonic looks also promising. harmonic factor is parametrizable with passthrough driver option 'harm=' to set n-th harmonic
    • reception in real world from antenna is very likely to require a suitable high pass or bandpass filter and an LNA in front of the RTLSDR dongle

  • passthrough driver options:

    • all the rtlsdr tools below support option '-O' followed by a ':' separated string of specific options, which are passed to the library by calling rtlsdr_set_opt_string().

    • process options from environment variable LIBRTLSDR_OPT for applications which don't support/use rtlsdr_set_opt_string() and don't support some of the features.

    • there are many options, e.g.

    • many of the options are R820T/2-tuner specific:

      • bc= set the the reception bands' center in Hz

      • sb= set tuner sideband

      • ifm= set IF mode (AGC, fixed gain, ..) for VGA (variable gain amplifier)

      • harm= set n-th harmonic reception

      • vcocmin= set minimum VCO current

      • vcocmax= set maximum VCO current

      • vcoalgo= set VCO algorithm

  • probably some more: it's highly probable, that this list is incomplete

"Driver" Library API

  • added rtlsdr_set_and_get_tuner_bandwidth(), which also delivers the bandwidth. [ with rtlsdr_set_tuner_bandwidth() does not deliver the bandwidth ]
  • added rtlsdr_set_tuner_band_center(), to set center of the filtered tuner band
  • added rtlsdr_set_tuner_sideband(), to set mixer sideband
  • added rtlsdr_set_tuner_gain_ext(), special for R820T/2 tuner
  • added rtlsdr_set_tuner_if_mode(), sets AGC modes in detail
  • added rtlsdr_set_dithering(), to allow disabling frequency dithering for R820T/2 tuner
  • added rtlsdr_set_ds_mode() including threshold frequency
  • added rtlsdr_ir_query()
  • added rtlsdr_set_opt_string() and rtlsdr_get_opt_help() for configuration of 'driver' - especially from command line. new alternative: environment variable LIBRTLSDR_OPT
  • added rtlsdr_set_tuner_i2c_register(), rtlsdr_get_tuner_i2c_register() and rtlsdr_set_tuner_i2c_override() exposing hacking of tuner-specific I2C registers
  • added rtlsdr_get_ver_id(), to allow discrimination between osmocom library - or this fork
  • added rtlsdr_get_version()
  • added rtlsdr_set_gpio_output(), rtlsdr_set_gpio_input(), rtlsdr_set_gpio_bit(), rtlsdr_get_gpio_bit(), rtlsdr_set_gpio_byte(), rtlsdr_get_gpio_byte() and rtlsdr_set_gpio_status()
  • added rtlsdr_set_center_freq64(), to set frequencies above ~4.29 GHz, the 32-bit limit
  • added rtlsdr_get_center_freq64()
  • added rtlsdr_set_harmonic_rx() to activate/change harmonic reception

Added Tools

  • added rtl_ir: display received IR signals.

    • requires the IR diode of an RTL-SDR - which might not exist!

  • added rtl_rpcd: a Remote Procedure Call server for RTL-SDR dongles.

    • for use, set environment variable "RTLSDR_RPC_IS_ENABLED"
    • optionally set environment varibales "RTLSDR_RPC_SERV_ADDR" and "RTLSDR_RPC_SERV_PORT". These default to "127.0.0.1" and "40000".
    • requires cmake option WITH_RPC

  • added rtl_raw2wav: save rtl_sdr or rtl_fm's output (pipe) into a wave file, including some meta information like timestamp and frequency

  • added rtl_udp: same as rtl_tcp - just using UDP instead of TCP

  • added rtl_wavestat: display wave file meta information

  • added rtl_wavestream: stream raw data (in specified format)

Improved Tools

  • rtl_fm:
    • added command file option '-C', which can trigger actions depending on signal. have a look at README.rtlfm_cmdfile.
    • added command line interface option '-E rdc', to enable dc blocking on raw I/Q data at capture rate
    • added CLI option '-E rtlagc', to enable rtl2832's digital agc
    • added CLI option '-E bclo', to use tuner bandwidths low corner as band center
    • added CLI option '-E bchi', to use tuner bandwidths high corner as band center
    • added CLI option '-O', to set RTL driver options separated with ':', e.g. -O 'bc=30000:agc=0'
    • added CLI option '-R', to specify number of seconds to run
    • added CLI option '-H', to write wave Header to file, producing a wave file with meta information, compatible with several SDR programs
    • added CLI option '-o', to request oversampling (4 recommended) for processing gain
  • rtl_biast:
    • several options for reading/writing other GPIOs
  • many tools have more options. compare all the details by starting with command line option '-h'.

"Driver" Library's UDP-Server

  • enabled by cmake option PROVIDE_UDP_SERVER for tests. OFF by default

  • activated by rtlsdr_set_opt_string(): "port=1" or "port=<udp_port>", default port number: 32323

  • purpose is to allow configuration at runtime with a simple text protocol, e.g. with netcat

  • for detailed protocol, see comment section in parse() of librtlsdr.c. or look for sections with '#ifdef WITH_UDP_SERVER'

  • this feature was copied and enhanced from https://sourceforge.net/projects/librtlsdr-wincontrol/ developed from sourceforge user randaller, which in turn is an adaption of https://github.com/gat3way/r820tweak, which was developed by Milen Rangelov

  • simple usage from command line, e.g. to retrieve help

    echo "h" | timeout 1 netcat -u 127.0.0.1 32323

    without timeout, press Ctrl+C the output is:

    g <register>                  # get content of I2C ..
s <register> <value> [<mask>] # set conten
S <register> <value> [<mask>] # set content - keeping value in future
i <IFfrequency>  # set IF frequency [0 .. 28'800'000]
f <RFfrequency>  # set center frequency
b <bandwidth>    # set tuner bandwidth
c <frequency>    # set tuner bw center in output [-1'600'000 .. 1'600'000]
v <sideband>     # set tuner sideband: 0 for LSB, 1 for USB
a <tunerIFmode>  # set VGA: 0 for auto; in tenth dB or 10000+idx
m <tuner gain>   # set tuner gain
M <gainMode>     # 0 .. 3: digital rtl agc (0..1) * 2 + tuner agc (0..1)

RTL_TCP TCP-PROTOCOL

  • allows non-GPL programs to utilize the RTLSDR stuff in a license compliant way

  • added several control functions in rtl_tcp, not existing in osmocom release: UDP_ESTABLISH, UDP_TERMINATE, SET_I2C_TUNER_REGISTER, SET_I2C_TUNER_OVERRIDE, SET_TUNER_BW_IF_CENTER, SET_TUNER_IF_MODE, SET_SIDEBAND, REPORT_I2C_REGS, SET_FREQ_HI32

  • control functions documented in rtl_tcp.h

  • (by default) control port number 1234, configurable via command-line-interface (CLI)

  • response(s) at +1 of control port: 1235, configurable via CLI

  • protocol details in protocol_rtl_tcp.txt