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#wfm-rpi

A simple FM receiver

WFM-rpi is software for the decoding of an FM signal. The software allows selecting a frequency through a small - separate - keypath, and it provides the possibility of saving a selected frequency, together with a user-selected name in a station list. One can add a station to the station list by selecting the frequency and pushing the "FS" button. Selecting a station (with the associated frequency) is by clicking ONCE the line in the station list. One can remove a line from the station list by clicking TWICE on the line. The software - obviously - supports decoding of rds.

The software has - just to experiment with - implemented 5 different algorithms for FM demodulation, user selectable.

The software can be configured for use with an AIRSPY, SDRplay and/or a DABstick.

The 1.0 version differs from the 0.998 version in two ways

• it allows configuration for more than one device, it will use
  the device attached.
• for the SDRplay, it now has an improved gain reduction setting, and
  it depends on library 2.13. In case an RSPduo is used, tuner 1 will we selected by default.

This version of the FM software was designed such that it runs on a Raspberry PI 2. The - high - input samplerate is filtered and decimated to a rate around 192000. Note that the load of processing FM at a rate of 192000 or higher is heavy. It turns out that by selecting the lto option for the compiler (gcc), the load is manageable and restricted to app 50-60 percent on all 4 cores of the RPI 2.

An option is to control the WFM-rpi software through an ssh connection from another computer (I use that since my Raspberry is not near my chair). To enable listening, a similar option as with the Qt-DAB software is implemented: the sound output can be send to an IP port.

Define STREAMER in CMake or undefine CONFIG+=streamer in the ".pro" file for installing a (simple) streamer that outputs the audio on port 20040 allowing you to listen from another computer. A simple "listener" is available as client, use qmake to build the listener, which is the same as for the Qt-DAB

For creating an executable: install the required libraries and use either qmake or CMake

The configuration file allows selection and incorporation of support of one of the mentioned devices. Note that selecting more than one of these devices in the configuration file lead to unexpected results.

The CMakeLists.txt file is written such that Qt5 is used. The "wfm-rpi.pro" file is less specific, both qmake-qt4 (for Qt4) and qmake-qt5 (for Qt5) gave good results.

The software compiles on the RPI 2, tested with Arch Linux and Jessie.

There might be an issue with sound on the RPI. Sound might be a little stuttering when the wrong buffersizes are selected.

Select buffersizes with "latency=X" in the "ini" file ($HOME/.wfm-rpi.ini) My favorite setting is 4.

After a first run, there will be an "ini" file with settings, just add a line latency=4 to test and adapt the value when there is stuttering

Note on DABSTICks

There has been quite some developments on the code for supporting dabsticks. This software assumes that there is a library "rtlsdr.." available. The easiest is to take the library from the osmocom site, however, there are other versions as well. You might want to try the version from Leif Albrink http://www.sm5bsz.com/linuxdsp/hware/rtlsdr/rtlsdr.htm

A good alternative (for me) was the one from http://www.rtl-sdr.com/new-experimental-r820t-rtl-sdr-driver-tunes-13-mhz-lower/

Selecting in the ".pro" file is by commenting or uncommenting lines

CONFIG+=dabstick

Similarly, comment or uncomment the definition lines in the top of the CMakeLists.txt file if you use cmake.

Note on SDRplay

The software is compiled against the 2.13 version of the SDRplay library, note that there is an incompatibility between 2.13 and its predecessors