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diff --git a/Documentation/video4linux/si4713.txt b/Documentation/video4linux/si4713.txt new file mode 100644 index 0000000..25abdb7 --- /dev/null +++ b/Documentation/video4linux/si4713.txt @@ -0,0 +1,176 @@ +Driver for I2C radios for the Silicon Labs Si4713 FM Radio Transmitters + +Copyright (c) 2009 Nokia Corporation +Contact: Eduardo Valentin <eduardo.valentin@nokia.com> + + +Information about the Device +============================ +This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 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. +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. + +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. + +When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. + +Properties description +====================== + +The properties can be accessed using v4l2 extended controls. +Here is an output from v4l2-ctl util: +/ # v4l2-ctl -d /dev/radio0 --all -L +Driver Info: + Driver name : radio-si4713 + Card type : Silicon Labs Si4713 Modulator + Bus info : + Driver version: 0 + Capabilities : 0x00080800 + RDS Output + Modulator +Audio output: 0 (FM Modulator Audio Out) +Frequency: 1408000 (88.000000 MHz) +Video Standard = 0x00000000 +Modulator: + Name : FM Modulator + Capabilities : 62.5 Hz stereo rds + Frequency range : 76.0 MHz - 108.0 MHz + Subchannel modulation: stereo+rds + +User Controls + + mute (bool) : default=1 value=0 + +FM Radio Modulator Controls + + rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider + rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 + rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 + rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' + rds_radio_text (str) : min=0 max=384 step=32 value='' + audio_limiter_feature_enabled (bool) : default=1 value=1 + audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider + audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider +audio_compression_feature_enabl (bool) : default=1 value=1 + audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider + audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider + audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider + audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider + pilot_tone_feature_enabled (bool) : default=1 value=1 + pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider + pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider + pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 + tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider + tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider +/ # + +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. + +* RDS related + +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 + +preemphasis - sets the preemphasis to be applied for transmission. + +RNL +=== + +This device also has an interface to measure received noise level. To do that, you should +ioctl the device node. Here is an code of example: + +int main (int argc, char *argv[]) +{ + struct si4713_rnl rnl; + int fd = open("/dev/radio0", O_RDWR); + int rval; + + if (argc < 2) + return -EINVAL; + + if (fd < 0) + return fd; + + sscanf(argv[1], "%d", &rnl.frequency); + + rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); + if (rval < 0) + return rval; + + printf("received noise level: %d\n", rnl.rnl); + + close(fd); +} + +The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under +include/media/si4713.h. + +Stereo/Mono and RDS subchannels +=============================== + +The device can also be configured using the available sub channels for +transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. +Refer to v4l2-spec for proper use of this ioctl. + +Testing +======= +Testing is usually done with v4l2-ctl utility for managing FM tuner cards. +The tool can be found in v4l-dvb repository under v4l2-apps/util directory. + +Example for setting rds ps name: +# v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" + |
