1.. include:: <isonum.txt> 2 3The Silicon Labs Si4713 FM Radio Transmitter Driver 4=================================================== 5 6Copyright |copy| 2009 Nokia Corporation 7 8Contact: Eduardo Valentin <eduardo.valentin@nokia.com> 9 10 11Information about the Device 12---------------------------- 13 14This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. 15Basically, it has transmission and signal noise level measurement features. 16 17The Si4713 integrates transmit functions for FM broadcast stereo transmission. 18The chip also allows integrated receive power scanning to identify low signal 19power FM channels. 20 21The chip is programmed using commands and responses. There are also several 22properties which can change the behavior of this chip. 23 24Users must comply with local regulations on radio frequency (RF) transmission. 25 26Device driver description 27------------------------- 28 29There are two modules to handle this device. One is a I2C device driver 30and the other is a platform driver. 31 32The I2C device driver exports a v4l2-subdev interface to the kernel. 33All properties can also be accessed by v4l2 extended controls interface, by 34using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). 35 36The platform device driver exports a v4l2 radio device interface to user land. 37So, it uses the I2C device driver as a sub device in order to send the user 38commands to the actual device. Basically it is a wrapper to the I2C device driver. 39 40Applications can use v4l2 radio API to specify frequency of operation, mute state, 41etc. But mostly of its properties will be present in the extended controls. 42 43When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. 44 45Properties description 46---------------------- 47 48The properties can be accessed using v4l2 extended controls. 49Here is an output from v4l2-ctl util: 50 51.. code-block:: none 52 53 / # v4l2-ctl -d /dev/radio0 --all -L 54 Driver Info: 55 Driver name : radio-si4713 56 Card type : Silicon Labs Si4713 Modulator 57 Bus info : 58 Driver version: 0 59 Capabilities : 0x00080800 60 RDS Output 61 Modulator 62 Audio output: 0 (FM Modulator Audio Out) 63 Frequency: 1408000 (88.000000 MHz) 64 Video Standard = 0x00000000 65 Modulator: 66 Name : FM Modulator 67 Capabilities : 62.5 Hz stereo rds 68 Frequency range : 76.0 MHz - 108.0 MHz 69 Subchannel modulation: stereo+rds 70 71 User Controls 72 73 mute (bool) : default=1 value=0 74 75 FM Radio Modulator Controls 76 77 rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider 78 rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 79 rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 80 rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' 81 rds_radio_text (str) : min=0 max=384 step=32 value='' 82 audio_limiter_feature_enabled (bool) : default=1 value=1 83 audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider 84 audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider 85 audio_compression_feature_enabl (bool) : default=1 value=1 86 audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider 87 audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider 88 audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider 89 audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider 90 pilot_tone_feature_enabled (bool) : default=1 value=1 91 pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider 92 pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider 93 pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 94 tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider 95 tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider 96 97Here is a summary of them: 98 99* Pilot is an audible tone sent by the device. 100 101- pilot_frequency - Configures the frequency of the stereo pilot tone. 102- pilot_deviation - Configures pilot tone frequency deviation level. 103- pilot_enabled - Enables or disables the pilot tone feature. 104 105* The si4713 device is capable of applying audio compression to the 106 transmitted signal. 107 108- acomp_enabled - Enables or disables the audio dynamic range control feature. 109- acomp_gain - Sets the gain for audio dynamic range control. 110- acomp_threshold - Sets the threshold level for audio dynamic range control. 111- acomp_attack_time - Sets the attack time for audio dynamic range control. 112- acomp_release_time - Sets the release time for audio dynamic range control. 113 114* Limiter setups audio deviation limiter feature. Once a over deviation occurs, 115 it is possible to adjust the front-end gain of the audio input and always 116 prevent over deviation. 117 118- limiter_enabled - Enables or disables the limiter feature. 119- limiter_deviation - Configures audio frequency deviation level. 120- limiter_release_time - Sets the limiter release time. 121 122* Tuning power 123 124- power_level - Sets the output power level for signal transmission. 125 antenna_capacitor - This selects the value of antenna tuning capacitor 126 manually or automatically if set to zero. 127 128* RDS related 129 130- rds_ps_name - Sets the RDS ps name field for transmission. 131- rds_radio_text - Sets the RDS radio text for transmission. 132- rds_pi - Sets the RDS PI field for transmission. 133- rds_pty - Sets the RDS PTY field for transmission. 134 135* Region related 136 137- preemphasis - sets the preemphasis to be applied for transmission. 138 139RNL 140--- 141 142This device also has an interface to measure received noise level. To do that, you should 143ioctl the device node. Here is an code of example: 144 145.. code-block:: none 146 147 int main (int argc, char *argv[]) 148 { 149 struct si4713_rnl rnl; 150 int fd = open("/dev/radio0", O_RDWR); 151 int rval; 152 153 if (argc < 2) 154 return -EINVAL; 155 156 if (fd < 0) 157 return fd; 158 159 sscanf(argv[1], "%d", &rnl.frequency); 160 161 rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); 162 if (rval < 0) 163 return rval; 164 165 printf("received noise level: %d\n", rnl.rnl); 166 167 close(fd); 168 } 169 170The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under 171include/linux/platform_data/media/si4713.h. 172 173Stereo/Mono and RDS subchannels 174------------------------------- 175 176The device can also be configured using the available sub channels for 177transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. 178Refer to the V4L2 API specification for proper use of this ioctl. 179 180Testing 181------- 182Testing is usually done with v4l2-ctl utility for managing FM tuner cards. 183The tool can be found in v4l-dvb repository under v4l2-apps/util directory. 184 185Example for setting rds ps name: 186 187.. code-block:: none 188 189 # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" 190 191
