# HG changeset patch # User Eduardo Valentin <eduardo.valentin@xxxxxxxxx> # Date 1243414607 -10800 # Branch export # Node ID fadf1cddf504609cdb4889f4aa3305ca8d15323a # Parent b1d98e675a3c4e9e6d247701c9ac18239e3dcc1c Signed-off-by: Eduardo Valentin <eduardo.valentin@xxxxxxxxx> --- Documentation/video4linux/si4713.txt | 133 ++++++++++++++++++++++++++++++++++ 1 files changed, 133 insertions(+), 0 deletions(-) create mode 100644 Documentation/video4linux/si4713.txt diff -r b1d98e675a3c -r fadf1cddf504 linux/Documentation/video4linux/si4713.txt --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/linux/Documentation/video4linux/si4713.txt Wed May 27 11:56:47 2009 +0300 @@ -0,0 +1,133 @@ +Driver for I2C radios for the Silicon Labs Si4713 FM Radio Transmitters + +Copyright (c) 2009 Nokia Corporation +Contact: Eduardo Valentin <eduardo.valentin@xxxxxxxxx> + + +Information about the Device +============================ +This chip is a Silicon Labs product. It is a I2C device, currently on 0Ã?63 address. +Basically, it has transmission and signal noise level measurement features. + +The Si4713 integrates transmit functions for FM broadcast stereo transmission. +The chip also allows integrated receive power scanning to identify low signal +power FM channels. + +The chip is programmed using commands and responses. There are also several +properties which can change the behavior of this chip. + +Users must comply with local regulations on radio frequency (RF) transmission. + +Device driver description +========================= +There are two modules to handle this device. One is a I2C device driver +and the other is a platform driver. + +The I2C device driver exports a v4l2-subdev interface to the kernel. Also +it exports several device properties through sysfs interface to the user land. +All properties can also be accessed by v4l2 extended controls interface, by +using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). + +The platform device driver exports a v4l2 radio device interface to user land. +So, it uses the I2C device driver as a sub device in order to send the user +commands to the actual device. Basically it is a wrapper to the I2C device driver. + +So, in summary, the device driver has two interfaces to the user space. + +Applications can use v4l2 radio API to specify frequency of operation, mute state, +etc. But mostly of its properties will be present in the extended controls. +However, the device properties can also be accessed through its sysfs directory. + +When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. + +Properties description +====================== + +The properties can be accessed in sysfs device directory. Using v4l2 extended +controls as well. + +# ls +acomp_attack_time modalias rds_radio_text +acomp_enabled name region +acomp_gain pilot_deviation region_bottom_frequency +acomp_release_time pilot_enabled region_channel_spacing +acomp_threshold pilot_frequency region_preemphasis +antenna_capacitor power region_top_frequency +bus power_level stereo_enabled +driver rds_enabled subsystem +limiter_deviation rds_pi tune_measure +limiter_enabled rds_ps_name uevent +limiter_release_time rds_pty + +Here is a summary of them: + +* Pilot is an audible tone sent by the device. + +pilot_frequency - Configures the frequency of the stereo pilot tone. +pilot_deviation - Configures pilot tone frequency deviation level. +pilot_enabled - Enables or disables the pilot tone feature. + +* The si4713 device is capable of applying audio compression to the transmitted signal. + +acomp_enabled - Enables or disables the audio dynamic range control feature. +acomp_gain - Sets the gain for audio dynamic range control. +acomp_threshold - Sets the threshold level for audio dynamic range control. +acomp_attack_time - Sets the attack time for audio dynamic range control. +acomp_release_time - Sets the release time for audio dynamic range control. + +* Limiter setups audio deviation limiter feature. Once a over deviation occurs, +it is possible to adjust the front-end gain of the audio input and always +prevent over deviation. + +limiter_enabled - Enables or disables the limiter feature. +limiter_deviation - Configures audio frequency deviation level. +limiter_release_time - Sets the limiter release time. + +* Tuning power + +power_level - Sets the output power level for signal transmission. +antenna_capacitor - This selects the value of antenna tuning capacitor manually +or automatically if set to zero. +tune_measure - With this you can get the value of signal length of a specific frequency. + +* RDS related + +rds_enabled - Enables or disables the RDS feature. +rds_ps_name - Sets the RDS ps name field for transmission. +rds_radio_text - Sets the RDS radio text for transmission. +rds_pi - Sets the RDS PI field for transmission. +rds_pty - Sets the RDS PTY field for transmission. + +* Region related + +Setting region will affect other region properties. + +region_bottom_frequency +region_channel_spacing +region_preemphasis +region_top_frequency +region - Selects which country specific setting should be assumed. + +* stereo_enabled - Enables or disables stereo mode. + +Testing +======= +Testing is usually done with fmtools utility for managing FM tuner cards. +The tool can be found under Debian/Testing packages. + +The basic command list is: + +$ fm on # Sets mute = false +$ fm off # Sets mute = true +$ fm <freq> # Tunes to the frequency <freq> + +Of course, you should have the audio working and play something through alsa +API to get something different of mute transmitted. + +To play with the above described properties, you can just use 'echo' and +'cat' commands. For example, changing the rds_ps_name property, you just do: + +echo "Dummy FM Station" > /sys/bus/i2c/devices/X-0063/rds_ps_name + +where "X" is the i2c bus id which the device is connected. + -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
