1Driver for I2C radios for the Silicon Labs Si4713 FM Radio Transmitters 2 3Copyright (c) 2009 Nokia Corporation 4Contact: Eduardo Valentin <eduardo.valentin@nokia.com> 5 6 7Information about the Device 8============================ 9This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. 10Basically, it has transmission and signal noise level measurement features. 11 12The Si4713 integrates transmit functions for FM broadcast stereo transmission. 13The chip also allows integrated receive power scanning to identify low signal 14power FM channels. 15 16The chip is programmed using commands and responses. There are also several 17properties which can change the behavior of this chip. 18 19Users must comply with local regulations on radio frequency (RF) transmission. 20 21Device driver description 22========================= 23There are two modules to handle this device. One is a I2C device driver 24and the other is a platform driver. 25 26The I2C device driver exports a v4l2-subdev interface to the kernel. 27All properties can also be accessed by v4l2 extended controls interface, by 28using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). 29 30The platform device driver exports a v4l2 radio device interface to user land. 31So, it uses the I2C device driver as a sub device in order to send the user 32commands to the actual device. Basically it is a wrapper to the I2C device driver. 33 34Applications can use v4l2 radio API to specify frequency of operation, mute state, 35etc. But mostly of its properties will be present in the extended controls. 36 37When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. 38 39Properties description 40====================== 41 42The properties can be accessed using v4l2 extended controls. 43Here is an output from v4l2-ctl util: 44/ # v4l2-ctl -d /dev/radio0 --all -L 45Driver 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 53Audio output: 0 (FM Modulator Audio Out) 54Frequency: 1408000 (88.000000 MHz) 55Video Standard = 0x00000000 56Modulator: 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 62User Controls 63 64 mute (bool) : default=1 value=0 65 66FM 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 76audio_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 89Here is a summary of them: 90 91* Pilot is an audible tone sent by the device. 92 93pilot_frequency - Configures the frequency of the stereo pilot tone. 94pilot_deviation - Configures pilot tone frequency deviation level. 95pilot_enabled - Enables or disables the pilot tone feature. 96 97* The si4713 device is capable of applying audio compression to the transmitted signal. 98 99acomp_enabled - Enables or disables the audio dynamic range control feature. 100acomp_gain - Sets the gain for audio dynamic range control. 101acomp_threshold - Sets the threshold level for audio dynamic range control. 102acomp_attack_time - Sets the attack time for audio dynamic range control. 103acomp_release_time - Sets the release time for audio dynamic range control. 104 105* Limiter setups audio deviation limiter feature. Once a over deviation occurs, 106it is possible to adjust the front-end gain of the audio input and always 107prevent over deviation. 108 109limiter_enabled - Enables or disables the limiter feature. 110limiter_deviation - Configures audio frequency deviation level. 111limiter_release_time - Sets the limiter release time. 112 113* Tuning power 114 115power_level - Sets the output power level for signal transmission. 116antenna_capacitor - This selects the value of antenna tuning capacitor manually 117or automatically if set to zero. 118 119* RDS related 120 121rds_ps_name - Sets the RDS ps name field for transmission. 122rds_radio_text - Sets the RDS radio text for transmission. 123rds_pi - Sets the RDS PI field for transmission. 124rds_pty - Sets the RDS PTY field for transmission. 125 126* Region related 127 128preemphasis - sets the preemphasis to be applied for transmission. 129 130RNL 131=== 132 133This device also has an interface to measure received noise level. To do that, you should 134ioctl the device node. Here is an code of example: 135 136int 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 159The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under 160include/media/si4713.h. 161 162Stereo/Mono and RDS subchannels 163=============================== 164 165The device can also be configured using the available sub channels for 166transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. 167Refer to the V4L2 API specification for proper use of this ioctl. 168 169Testing 170======= 171Testing is usually done with v4l2-ctl utility for managing FM tuner cards. 172The tool can be found in v4l-dvb repository under v4l2-apps/util directory. 173 174Example for setting rds ps name: 175# v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" 176 177