| 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 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: | |
| # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" | |