MiniRDS

This program is designed for generating a realtime RDS signal. It is capable of RDS2 using up to 3 additional subcarriers.

This is based on the RDS encoder from Mpxgen, which is currently not maintained.

Note that some missing groups were added from librds, my other project

Features

• Low resource requirements
• Support for basic RDS data fields: PS, RT, PTY and AF
• RDS items can be updated through control pipe
• RT+ support
• RDS2 support (including station logo transmission)

To do

• Threading

Planned features

• UECP
• Configuration file

What are the changes from normal MiniRDS?

• CMake
• better arguments
• Option to disable ODA
• Better Group Sequence (original had 0A 2A but here it is 0A 0A 0A 0A 2A 2A 2A 2A (2A) so PS appear instantly and RT is fast)
• Added LIC and PIN
• Most commands are compatible with the ASCII format that pira.cz uses
• Custom groups (use G=BBBBCCCCDDDD or CG AAAA BBBB CCCC DDDD)
• Mono! mono? Mono! Not stereo! why? because the 2 channels were exactly the same in the first place so there was no point in having a 2nd one

Build

For Debian-like distros: sudo apt-get install libao-dev libsamplerate0-dev to install deps.

Note that MiniRDS requires CMake to compile (install with sudo apt install cmake)

Once those are installed, run

git clone https://flerken.zapto.org:1115/kuba/minirds
cd minirds/src
mkdir build
cd build
cmake ..
make
sudo make install

How to use

Simply run:

minirds

to confirm proper operation.

Please see -h for more options.

Stereo Tool integration

The following setup allows MiniRDS to be used alongside Stereo Tool audio processor.

.-------------.
| Stereo Tool |--(FM MPX w/o RDS)-----.
'-------------'                       |
                                      v
                           .-----------------------.
                           |       ALSA dmixer     |
                           | slave: MPX sound card |--------(to sound card)-------->
                           |        192 kHz        |
                           '-----------------------'
                                      ^
.---------.                           |
| MiniRDS |--(RDS output)-------------'
'---------'

First, add the following contents to ~/.asoundrc:

# ST MPX output
pcm.mpxmix {
  type dmix
  ipc_key 1001
  slave {
    pcm "digital-out" # change to your actual sound card
    rate 192000
  }
}

Next, add the collowing contents to ~/.ao:

dev=mpxmix

Then set the Stereo Tool MPX output to use the ALSA "mpxmix" output. Finally run minirds. Adjust volumes accordingly.

Note that this setup is not optimal. Hans plans to add RDS2 passthough to the ST external RDS input. Stereo Tool forum post

If you need to you also can run MiniRDS on a ST transmitter modulated as mono audio, which does work however on some TXs the RDS signal may not be great due to harmonics of ST Pilot Tone

Changing PS, RT, TA and PTY at run-time

You can control PS, RT, TA (Traffic Announcement flag), PTY (Program Type) and many other items at run-time using a named pipe (FIFO). For this run MiniRDS with the --ctl argument.

Scripts can be written to obtain and send "now playing" text data to MiniRDS for dynamic RDS.

See the command list for a complete list of valid commands.

RDS2

MiniRDS has a working implementation of the RFT protocol in RDS2. Please edit the Makefile accordingly and rebuild for RDS2 capabilities. You may use your own image by using the provided "make-station-logo.sh" script. Valid formats are PNG or JPG and should be about 3kB or less. Larger images take considerably longer to receive.

References

• EN 50067, Specification of the radio data system (RDS) for VHF/FM sound broadcasting in the frequency range 87.5 to 108.0 MHz
• IEC 62106-2, Radio data system (RDS) – Part 2: Message format: coding and definitions of RDS features
• IEC 62106-3, Radio data system (RDS) – Part 3: Usage and registration of Open Data Applications (ODAs)
• IEC 62106-4, Radio data system (RDS) – Part 4: Registered code tables
• IEC 62106-6, Radio data system (RDS) – Part 6: Compilation of technical specifications for Open Data Applications in the public domain
• P232 RDS Encoder Technical Manual
• PIRA32 RDS Encoder Technical Manual

Credits

Note that this is a fork of Anthony96922's MiniRDS

The RDS waveform generator was adapted from PiFmRds