Installing dsd-fme and setup for P25 scanning on a Raspberry Pi

dsd-fme can decode a variety of digital voice formats. This page will concentrate on a P25 scanner configuration.

Install:

• dsd-fme
  Digital Speech Decoder - Florida Man Edition
  • Prerequisites
    • MBElib from Installing SDR applications on a Raspberry Pi and Debian
    • Hamlib from Installing utility software on a Raspberry Pi
    • Install packages

      sudo apt install libpulse-dev pavucontrol libsndfile1-dev libfftw3-dev liblapack-dev socat libusb-1.0-0-dev rtl-sdr librtlsdr-dev libusb-1.0-0-dev cmake git wget make build-essential libitpp-dev libncurses-dev libncurses6 libcodec2-dev

  • Build and install

    cd ~/
    git clone https://github.com/lwvmobile/dsd-fme
    cd dsd-fme
    mkdir build
    cd build
    cmake ..
    make -j `nproc`
    sudo make install
    sudo ldconfig
    

  • Configuring dsd-fme for a P25 trunked system. Put the configuration files in ~/dsd-fme
    For more information, go to https://github.com/lwvmobile/dsd-fme/blob/audio_work/examples/Install_Notes.md
    
    • Make a groups file containing all of your talkgroups. Open a sample file in a spreadsheet:
      • Sample groups file
      • Find your system on https://www.radioreference.com/ and go to the talkgroups.
      • You can paste them into a spreadsheet, where you can manipulate the data into the format of the sample file. Save as .csv
        If you are a member of radioreference.com, you can download a list, which makes it much easier.
    • Make a channel map file. See https://www.radioreference.com/
      You could also start the SDR receiver tuned to the current control channel. If you don't have a channel map file, it will search for the control channel.
      Open a sample file in a spreadsheet:
      • Sample Channel Map file
      • Add your control channels with the default control channel first. Save as .csv

• Usage notes
  • Scanning using SDR++
    This method allows you to use a variety of SDRs.
    • SDR++ must have been installed previously
    • In SDR++, configure the following settings:
      • Under the Radio pull-down
        • Select NFM
          
        • In Bandwidth, enter 12500 Hz to 15000 Hz, whatever works for you.
        • Select De-emphasis None
        • Select Low Pass
      • Under the Radio section
        • Expand the pull-down nearest the top.
        • Select network
          The host should be localhost, port 7355
        • Select Protocol TCP
        • Samplerate should be 48000
        • Press start
      • Under the Rigctl Server pull-down
        
        • The host should be localhost, port 4532
        • Select Tuning
        • Press start
          
      • Tune SDR++ to the current control channel if you need a quicker startup.
      • Click the Play button
    • Start dsd-fme
      Using your channel map and group list, for example

      # In terminal #1
      cd ~/dsd-fme
      dsd-fme -i tcp -T -U 4532 -C michigan_channel_map.csv -G michigan.csv -N 2> console_log.txt
      
      # In terminal #2
      cd ~/dsd-fme
      tail -f console_log.txt
      

  • dsd-fme can be configured to use a virtual audio cable, other SDR software such as gqrx.
  • Scanning using an RTL-SDR

    # In terminal #1
    cd ~/dsd-fme
    dsd-fme -ft -i rtl:0:855.2875M:0:0:12:0:2 -T -C michigan_channel_map.csv -G michigan.csv -N 2> console_log.txt
    
    # In terminal #2
    cd ~/dsd-fme
    tail -f console_log.txt
    

  • Press Q to exit dsd-fme.