| .. include:: <isonum.txt> |
| |
| The Silicon Labs Si4713 FM Radio Transmitter Driver |
| =================================================== |
| |
| Copyright |copy| 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: |
| |
| .. code-block:: none |
| |
| / # 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: |
| |
| .. code-block:: none |
| |
| 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/linux/platform_data/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 the V4L2 API specification 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: |
| |
| .. code-block:: none |
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| # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" |
| |