119 lines
4.3 KiB
Plaintext
119 lines
4.3 KiB
Plaintext
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Driver for USB radios for the Silicon Labs Si470x FM Radio Receivers
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Copyright (c) 2008 Tobias Lorenz <tobias.lorenz@gmx.net>
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Information from Silicon Labs
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=============================
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Silicon Laboratories is the manufacturer of the radio ICs, that nowadays are the
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most often used radio receivers in cell phones. Usually they are connected with
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I2C. But SiLabs also provides a reference design, which integrates this IC,
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together with a small microcontroller C8051F321, to form a USB radio.
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Part of this reference design is also a radio application in binary and source
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code. The software also contains an automatic firmware upgrade to the most
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current version. Information on these can be downloaded here:
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http://www.silabs.com/usbradio
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Supported ICs
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=============
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The following ICs have a very similar register set, so that they are or will be
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supported somewhen by the driver:
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- Si4700: FM radio receiver
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- Si4701: FM radio receiver, RDS Support
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- Si4702: FM radio receiver
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- Si4703: FM radio receiver, RDS Support
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- Si4704: FM radio receiver, no external antenna required
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- Si4705: FM radio receiver, no external antenna required, RDS support, Dig I/O
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- Si4706: Enhanced FM RDS/TMC radio receiver, no external antenna required, RDS
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Support
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- Si4707: Dedicated weather band radio receiver with SAME decoder, RDS Support
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- Si4708: Smallest FM receivers
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- Si4709: Smallest FM receivers, RDS Support
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More information on these can be downloaded here:
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http://www.silabs.com/products/mcu/Pages/USBFMRadioRD.aspx
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Supported USB devices
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=====================
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Currently the following USB radios (vendor:product) with the Silicon Labs si470x
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chips are known to work:
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- 10c4:818a: Silicon Labs USB FM Radio Reference Design
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- 06e1:a155: ADS/Tech FM Radio Receiver (formerly Instant FM Music) (RDX-155-EF)
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- 1b80:d700: KWorld USB FM Radio SnapMusic Mobile 700 (FM700)
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Software
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========
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Testing is usually done with most application under Debian/testing:
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- fmtools - Utility for managing FM tuner cards
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- gnomeradio - FM-radio tuner for the GNOME desktop
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- gradio - GTK FM radio tuner
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- kradio - Comfortable Radio Application for KDE
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- radio - ncurses-based radio application
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There is also a library libv4l, which can be used. It's going to have a function
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for frequency seeking, either by using hardware functionality as in radio-si470x
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or by implementing a function as we currently have in every of the mentioned
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programs. Somewhen the radio programs should make use of libv4l.
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For processing RDS information, there is a project ongoing at:
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http://rdsd.berlios.de/
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There is currently no project for making TMC sentences human readable.
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Audio Listing
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=============
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USB Audio is provided by the ALSA snd_usb_audio module. It is recommended to
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also select SND_USB_AUDIO, as this is required to get sound from the radio. For
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listing you have to redirect the sound, for example using one of the following
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commands.
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If you just want to test audio (very poor quality):
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cat /dev/dsp1 > /dev/dsp
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If you use OSS try:
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sox -2 --endian little -r 96000 -t oss /dev/dsp1 -t oss /dev/dsp
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If you use arts try:
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arecord -D hw:1,0 -r96000 -c2 -f S16_LE | artsdsp aplay -B -
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Module Parameters
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=================
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After loading the module, you still have access to some of them in the sysfs
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mount under /sys/module/radio_si470x/parameters. The contents of read-only files
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(0444) are not updated, even if space, band and de are changed using private
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video controls. The others are runtime changeable.
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Errors
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======
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Increase tune_timeout, if you often get -EIO errors.
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When timed out or band limit is reached, hw_freq_seek returns -EAGAIN.
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If you get any errors from snd_usb_audio, please report them to the ALSA people.
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Open Issues
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===========
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V4L minor device allocation and parameter setting is not perfect. A solution is
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currently under discussion.
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There is an USB interface for downloading/uploading new firmware images. Support
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for it can be implemented using the request_firmware interface.
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There is a RDS interrupt mode. The driver is already using the same interface
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for polling RDS information, but is currently not using the interrupt mode.
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There is a LED interface, which can be used to override the LED control
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programmed in the firmware. This can be made available using the LED support
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functions in the kernel.
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Other useful information and links
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==================================
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http://www.silabs.com/usbradio
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