Radio Service
Overview
Radio Service allows tuning of rtl-sdr based devices to radio stations and receive respective audio stream.
Verbs
| Name | Description | JSON Parameters |
|---|---|---|
| subscribe | subscribe to radio events | Request: {"value": "frequency"} |
| unsubscribe | unsubscribe to radio events | Request: {"value": "frequency"} |
| frequency | get/set tuned radio frequency | Request: {"value": 101100000} |
| band | get/set current band type (e.g. AM, FM) | Request: {"band": "FM"} Response: {"band": "FM"} |
| band_supported | check if a certain band is supported | Request: {"band": "FM"} Response: {"supported": 1} |
| frequency_range | get frequency range for band type | Request: {"band": "FM"} Response: {"min": ..., "max": ...} |
| frequency_step | get frequency step/spacing for band type | Request: {"band": "FM"} Response: {"step": 200000} |
| start | start radio playback | |
| stop | stop radio playback | |
| scan_start | start scanning for station | Request: {"direction": "forward" or "backward"} |
| scan_stop | stop scanning for station | |
| stereo_mode | get/set stereo or mono mode | Request: {"value": "stereo" or "mono"} |
Events
frequency Event JSON Response
JSON response has a single field frequency which is the currently tuned frequency.
station_found Event JSON Response
JSON response has a single field value of the frequency of the discovered radio station.
status Event JSON Response
JSON response has a single field value with one of the values "playing" or "stopped".
AGL Radio Tuner Binding
FM Band Plan Selection
The FM band plan may be selected by adding:
fmbandplan=X
to the [radio] section in /etc/xdg/AGL.conf, where X is one of the following strings:
US = United States / Canada JP = Japan EU = European Union ITU-1 ITU-2
Example:
[radio]
fmbandplan=JP
Implementation Specific Confguration
USB RTL-SDR adapter
The scanning sensitivity can be tweaked by adding:
scan_squelch_level=X
to the [radio] section in /etc/xdg/AGL.conf, where X is an integer. Lower values make the scanning more sensitive. Default value is 140.
Example:
[radio]
scan_squelch_level=70
M3ULCB Kingfisher Si4689
The scanning sensitivity can be tweaked by adding:
scan_valid_snr_threshold=X
scan_valid_rssi_threshold=Y
to the [radio] section in /etc/xdg/AGL.conf, where X and Y are integers between -127 and 127. The SNR value is in units of dB, and the RSSI is in units of dBuV. Lower values make the scanning more sensitive. Default values in the Si4689 are 10 and 17, respectively. You may determine the values that the Si4689 is seeing when tuning by examining the results of tuning in the systemd journal, looking for lines like:
Example:
[radio]
scan_valid_snr_threshold=7
scan_valid_rssi_threshold=10
Known Issues
M3ULCB Kingfisher
Initial setup for a new Kingfisher board requires booting an image with Kingfisher support and running the commands:
si_init
si_firmware_update
This installs the provided firmware into the flash attached to the Si4689.
Since all operations are currently done by calling a patched version of Cogent Embedded's si_ctl utility, scanning currently cannot be interrupted. Additionally, sometimes a failure in scanning seems to result in muted state that currently has not been debugged.