Documentation/media/v4l-drivers/si4713.rst

   1 .. include:: <isonum.txt>
   2
   3 The Silicon Labs Si4713 FM Radio Transmitter Driver
   4 ===================================================
   5
   6 Copyright |copy| 2009 Nokia Corporation
   7
   8 Contact: Eduardo Valentin <eduardo.valentin@nokia.com>
   9
  10
  11 Information about the Device
  12 ----------------------------
  13
  14 This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address.
  15 Basically, it has transmission and signal noise level measurement features.
  16
  17 The Si4713 integrates transmit functions for FM broadcast stereo transmission.
  18 The chip also allows integrated receive power scanning to identify low signal
  19 power FM channels.
  20
  21 The chip is programmed using commands and responses. There are also several
  22 properties which can change the behavior of this chip.
  23
  24 Users must comply with local regulations on radio frequency (RF) transmission.
  25
  26 Device driver description
  27 -------------------------
  28
  29 There are two modules to handle this device. One is a I2C device driver
  30 and the other is a platform driver.
  31
  32 The I2C device driver exports a v4l2-subdev interface to the kernel.
  33 All properties can also be accessed by v4l2 extended controls interface, by
  34 using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls).
  35
  36 The platform device driver exports a v4l2 radio device interface to user land.
  37 So, it uses the I2C device driver as a sub device in order to send the user
  38 commands to the actual device. Basically it is a wrapper to the I2C device driver.
  39
  40 Applications can use v4l2 radio API to specify frequency of operation, mute state,
  41 etc. But mostly of its properties will be present in the extended controls.
  42
  43 When the v4l2 mute property is set to 1 (true), the driver will turn the chip off.
  44
  45 Properties description
  46 ----------------------
  47
  48 The properties can be accessed using v4l2 extended controls.
  49 Here 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
  97 Here 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
 139 RNL
 140 ---
 141
 142 This device also has an interface to measure received noise level. To do that, you should
 143 ioctl 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
 170 The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under
 171 include/linux/platform_data/media/si4713.h.
 172
 173 Stereo/Mono and RDS subchannels
 174 -------------------------------
 175
 176 The device can also be configured using the available sub channels for
 177 transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly.
 178 Refer to the V4L2 API specification for proper use of this ioctl.
 179
 180 Testing
 181 -------
 182 Testing is usually done with v4l2-ctl utility for managing FM tuner cards.
 183 The tool can be found in v4l-dvb repository under v4l2-apps/util directory.
 184
 185 Example for setting rds ps name:
 186
 187 .. code-block:: none
 188
 189         # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy"
 190