Thank you to Hayati Ayguen for letting us know that he and others have submitted a slew of updates to the "librtlsdr" fork of the librtlsdr RTL-SDR drivers. The improvements made to the development branch are extensive and are pasted below, and Hayati also has also created some presentation slides about his improvements. Hayati also notes that there are several open issues being tracked, and he has labelled some as "help wanted" where help and testing would be appreciated.
If you have tested any of the new features of tools, please let us know how they work in the comments!
"Driver" Library Features
added support for special USB (vendor) VID 0x1209 (product) PID 0x2832: "Generic RTL2832U":
added smaller bandwidths, improving selectivity: 290, 375, 420, 470, 600, 860, 950, 1100, 1300, 1500, 1600, 1750, 1950 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).
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()
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_ds_mode() including threshold frequency
added rtlsdr_set_opt_string() and rtlsdr_get_opt_help() for configuration of 'driver' - especially from command line
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 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)
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 seperated 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
not just rtl_fm, but many tools have more options. compare all the details by starting with command line option '-h'.
"Driver" Library's UDP-Server - only on Windows
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'
allows non-GPL programs, e.g. QIRX, 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
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
Fabien built a remote SDR using a BeagleBone Black mini embedded computer and put it outside for better reception and to be closer to the antenna. When trying to remotely access the dongle he discovered some problems. He writes:
I then access the dongle over TCP from an indoor PC. One issue is that some existing tools such as rtl_fm, rtlizer or rtlsdr_waterfall lacks TCP/IP connectivity.
To solve this problem, I added TCP support to the rtlsdr library. When a tool communicates with the now physically distant dongle, this new implementation transparently forwards the data using TCP instead of USB. It allows one to use existing tools without modifying them. Also, it allows a developer to use the same librtlsdr, no matter whether the dongle is local or distant.
To use it, one must compile and install the library. Then, a server (called rtl_rpcd) must be run on the remote location (in my case, the beagle bone black at address 192.168.0.43): RTLSDR_RPC_SERV_ADDR=192.168.0.43 \ rtl_rpcd
Then, the existing tool (for instance rtlizer) can be run using:
RTLSDR_RPC_IS_ENABLED=1 RTLSDR_RPC_SERV_ADDR=192.168.0.43 \