RDS/RBDS FM receiver (external) for traffic conditions

Joshua Layne joshua at willowisp.net
Sun Nov 18 20:12:45 CET 2007

Doug Sutherland wrote:
> Josh,
> I have the USB FM radio stick.
> A USB audio device does appear when it's plugged in.
> However, there is no audio until the FM radio app is run.
> This does SPI communication with the SI4701 to init
> and change its settings.
>> They claim it uses standard USBaudio for the sound and that they use the
>> HID spec for control interface (which doesn't make a ton of sense to me,
>> as it seems backwards, but I have not reviewed the spec).
> Why would this be backwards?
I have always thought of HID as using an external device that then 
communicates to the computer, this is using a virtual app on the 
computer to control an external device - I don't disagree that it is 
Human Interface.
> HID is human interface, which in this case is buttons on the FM radio
> GUI application, you have a stereo/mono select, volume slider, mute button,
> up and down frequency tune and scan buttons, a button for configuring the
> preset stations, and buttons for preset stations. What is backwards about
> this? Audio is standard USB audio, controls are custom "generic USB HID".
>> This is also the FM chip used in the M$ Zune, but there doesn't appear
>> to have been a lot of progress made on the linux front there.
> I haven't looked at the code for the FM radio application, and have no
> idea about making this existing application work with linux. There is
> other source code also for the evaluation board for the chips.
> The FM radio stick doesn't appear to demo any RDS/RBDS capability,
> at least not where I am, no station or artist/song names are appearing.
Interesting - they claim it does, but it may not be present in the GUI 
they provide - there certainly is code in the source they provide.
I don't think the firmware would need to be reflashed - it would just 
need the proper command.

Thanks for the detailed replies.

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