Eduardo Valentin | 436e7e7 | 2009-08-08 09:01:34 -0300 | [diff] [blame] | 1 | Driver for I2C radios for the Silicon Labs Si4713 FM Radio Transmitters |
| 2 | |
| 3 | Copyright (c) 2009 Nokia Corporation |
| 4 | Contact: Eduardo Valentin <eduardo.valentin@nokia.com> |
| 5 | |
| 6 | |
| 7 | Information about the Device |
| 8 | ============================ |
| 9 | This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. |
| 10 | Basically, it has transmission and signal noise level measurement features. |
| 11 | |
| 12 | The Si4713 integrates transmit functions for FM broadcast stereo transmission. |
| 13 | The chip also allows integrated receive power scanning to identify low signal |
| 14 | power FM channels. |
| 15 | |
| 16 | The chip is programmed using commands and responses. There are also several |
| 17 | properties which can change the behavior of this chip. |
| 18 | |
| 19 | Users must comply with local regulations on radio frequency (RF) transmission. |
| 20 | |
| 21 | Device driver description |
| 22 | ========================= |
| 23 | There are two modules to handle this device. One is a I2C device driver |
| 24 | and the other is a platform driver. |
| 25 | |
| 26 | The I2C device driver exports a v4l2-subdev interface to the kernel. |
| 27 | All properties can also be accessed by v4l2 extended controls interface, by |
| 28 | using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). |
| 29 | |
| 30 | The platform device driver exports a v4l2 radio device interface to user land. |
| 31 | So, it uses the I2C device driver as a sub device in order to send the user |
| 32 | commands to the actual device. Basically it is a wrapper to the I2C device driver. |
| 33 | |
| 34 | Applications can use v4l2 radio API to specify frequency of operation, mute state, |
| 35 | etc. But mostly of its properties will be present in the extended controls. |
| 36 | |
| 37 | When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. |
| 38 | |
| 39 | Properties description |
| 40 | ====================== |
| 41 | |
| 42 | The properties can be accessed using v4l2 extended controls. |
| 43 | Here is an output from v4l2-ctl util: |
| 44 | / # v4l2-ctl -d /dev/radio0 --all -L |
| 45 | Driver Info: |
| 46 | Driver name : radio-si4713 |
| 47 | Card type : Silicon Labs Si4713 Modulator |
| 48 | Bus info : |
| 49 | Driver version: 0 |
| 50 | Capabilities : 0x00080800 |
| 51 | RDS Output |
| 52 | Modulator |
| 53 | Audio output: 0 (FM Modulator Audio Out) |
| 54 | Frequency: 1408000 (88.000000 MHz) |
| 55 | Video Standard = 0x00000000 |
| 56 | Modulator: |
| 57 | Name : FM Modulator |
| 58 | Capabilities : 62.5 Hz stereo rds |
| 59 | Frequency range : 76.0 MHz - 108.0 MHz |
| 60 | Subchannel modulation: stereo+rds |
| 61 | |
| 62 | User Controls |
| 63 | |
| 64 | mute (bool) : default=1 value=0 |
| 65 | |
| 66 | FM Radio Modulator Controls |
| 67 | |
| 68 | rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider |
| 69 | rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 |
| 70 | rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 |
| 71 | rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' |
| 72 | rds_radio_text (str) : min=0 max=384 step=32 value='' |
| 73 | audio_limiter_feature_enabled (bool) : default=1 value=1 |
| 74 | audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider |
| 75 | audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider |
| 76 | audio_compression_feature_enabl (bool) : default=1 value=1 |
| 77 | audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider |
| 78 | audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider |
| 79 | audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider |
| 80 | audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider |
| 81 | pilot_tone_feature_enabled (bool) : default=1 value=1 |
| 82 | pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider |
| 83 | pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider |
| 84 | pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 |
| 85 | tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider |
| 86 | tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider |
| 87 | / # |
| 88 | |
| 89 | Here is a summary of them: |
| 90 | |
| 91 | * Pilot is an audible tone sent by the device. |
| 92 | |
| 93 | pilot_frequency - Configures the frequency of the stereo pilot tone. |
| 94 | pilot_deviation - Configures pilot tone frequency deviation level. |
| 95 | pilot_enabled - Enables or disables the pilot tone feature. |
| 96 | |
| 97 | * The si4713 device is capable of applying audio compression to the transmitted signal. |
| 98 | |
| 99 | acomp_enabled - Enables or disables the audio dynamic range control feature. |
| 100 | acomp_gain - Sets the gain for audio dynamic range control. |
| 101 | acomp_threshold - Sets the threshold level for audio dynamic range control. |
| 102 | acomp_attack_time - Sets the attack time for audio dynamic range control. |
| 103 | acomp_release_time - Sets the release time for audio dynamic range control. |
| 104 | |
| 105 | * Limiter setups audio deviation limiter feature. Once a over deviation occurs, |
| 106 | it is possible to adjust the front-end gain of the audio input and always |
| 107 | prevent over deviation. |
| 108 | |
| 109 | limiter_enabled - Enables or disables the limiter feature. |
| 110 | limiter_deviation - Configures audio frequency deviation level. |
| 111 | limiter_release_time - Sets the limiter release time. |
| 112 | |
| 113 | * Tuning power |
| 114 | |
| 115 | power_level - Sets the output power level for signal transmission. |
| 116 | antenna_capacitor - This selects the value of antenna tuning capacitor manually |
| 117 | or automatically if set to zero. |
| 118 | |
| 119 | * RDS related |
| 120 | |
| 121 | rds_ps_name - Sets the RDS ps name field for transmission. |
| 122 | rds_radio_text - Sets the RDS radio text for transmission. |
| 123 | rds_pi - Sets the RDS PI field for transmission. |
| 124 | rds_pty - Sets the RDS PTY field for transmission. |
| 125 | |
| 126 | * Region related |
| 127 | |
| 128 | preemphasis - sets the preemphasis to be applied for transmission. |
| 129 | |
| 130 | RNL |
| 131 | === |
| 132 | |
| 133 | This device also has an interface to measure received noise level. To do that, you should |
| 134 | ioctl the device node. Here is an code of example: |
| 135 | |
| 136 | int main (int argc, char *argv[]) |
| 137 | { |
| 138 | struct si4713_rnl rnl; |
| 139 | int fd = open("/dev/radio0", O_RDWR); |
| 140 | int rval; |
| 141 | |
| 142 | if (argc < 2) |
| 143 | return -EINVAL; |
| 144 | |
| 145 | if (fd < 0) |
| 146 | return fd; |
| 147 | |
| 148 | sscanf(argv[1], "%d", &rnl.frequency); |
| 149 | |
| 150 | rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); |
| 151 | if (rval < 0) |
| 152 | return rval; |
| 153 | |
| 154 | printf("received noise level: %d\n", rnl.rnl); |
| 155 | |
| 156 | close(fd); |
| 157 | } |
| 158 | |
| 159 | The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under |
| 160 | include/media/si4713.h. |
| 161 | |
| 162 | Stereo/Mono and RDS subchannels |
| 163 | =============================== |
| 164 | |
| 165 | The device can also be configured using the available sub channels for |
| 166 | transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. |
| 167 | Refer to v4l2-spec for proper use of this ioctl. |
| 168 | |
| 169 | Testing |
| 170 | ======= |
| 171 | Testing is usually done with v4l2-ctl utility for managing FM tuner cards. |
| 172 | The tool can be found in v4l-dvb repository under v4l2-apps/util directory. |
| 173 | |
| 174 | Example for setting rds ps name: |
| 175 | # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" |
| 176 | |