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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
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3 | .. include:: <isonum.txt> |
4 | ||
5 | The Silicon Labs Si4713 FM Radio Transmitter Driver | |
6 | =================================================== | |
7 | ||
8 | Copyright |copy| 2009 Nokia Corporation | |
436e7e7c | 9 | |
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10 | Contact: Eduardo Valentin <eduardo.valentin@nokia.com> |
11 | ||
12 | ||
13 | Information about the Device | |
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14 | ---------------------------- |
15 | ||
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16 | This chip is a Silicon Labs product. It is a I2C device, currently on 0x63 address. |
17 | Basically, it has transmission and signal noise level measurement features. | |
18 | ||
19 | The Si4713 integrates transmit functions for FM broadcast stereo transmission. | |
20 | The chip also allows integrated receive power scanning to identify low signal | |
21 | power FM channels. | |
22 | ||
23 | The chip is programmed using commands and responses. There are also several | |
24 | properties which can change the behavior of this chip. | |
25 | ||
26 | Users must comply with local regulations on radio frequency (RF) transmission. | |
27 | ||
28 | Device driver description | |
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29 | ------------------------- |
30 | ||
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31 | There are two modules to handle this device. One is a I2C device driver |
32 | and the other is a platform driver. | |
33 | ||
34 | The I2C device driver exports a v4l2-subdev interface to the kernel. | |
35 | All properties can also be accessed by v4l2 extended controls interface, by | |
36 | using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls). | |
37 | ||
38 | The platform device driver exports a v4l2 radio device interface to user land. | |
39 | So, it uses the I2C device driver as a sub device in order to send the user | |
40 | commands to the actual device. Basically it is a wrapper to the I2C device driver. | |
41 | ||
42 | Applications can use v4l2 radio API to specify frequency of operation, mute state, | |
43 | etc. But mostly of its properties will be present in the extended controls. | |
44 | ||
45 | When the v4l2 mute property is set to 1 (true), the driver will turn the chip off. | |
46 | ||
47 | Properties description | |
b2993570 | 48 | ---------------------- |
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49 | |
50 | The properties can be accessed using v4l2 extended controls. | |
51 | Here is an output from v4l2-ctl util: | |
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52 | |
53 | .. code-block:: none | |
54 | ||
55 | / # v4l2-ctl -d /dev/radio0 --all -L | |
56 | Driver Info: | |
57 | Driver name : radio-si4713 | |
58 | Card type : Silicon Labs Si4713 Modulator | |
59 | Bus info : | |
60 | Driver version: 0 | |
61 | Capabilities : 0x00080800 | |
62 | RDS Output | |
63 | Modulator | |
64 | Audio output: 0 (FM Modulator Audio Out) | |
65 | Frequency: 1408000 (88.000000 MHz) | |
66 | Video Standard = 0x00000000 | |
67 | Modulator: | |
68 | Name : FM Modulator | |
69 | Capabilities : 62.5 Hz stereo rds | |
70 | Frequency range : 76.0 MHz - 108.0 MHz | |
71 | Subchannel modulation: stereo+rds | |
72 | ||
73 | User Controls | |
74 | ||
75 | mute (bool) : default=1 value=0 | |
76 | ||
77 | FM Radio Modulator Controls | |
78 | ||
79 | rds_signal_deviation (int) : min=0 max=90000 step=10 default=200 value=200 flags=slider | |
80 | rds_program_id (int) : min=0 max=65535 step=1 default=0 value=0 | |
81 | rds_program_type (int) : min=0 max=31 step=1 default=0 value=0 | |
82 | rds_ps_name (str) : min=0 max=96 step=8 value='si4713 ' | |
83 | rds_radio_text (str) : min=0 max=384 step=32 value='' | |
84 | audio_limiter_feature_enabled (bool) : default=1 value=1 | |
85 | audio_limiter_release_time (int) : min=250 max=102390 step=50 default=5010 value=5010 flags=slider | |
86 | audio_limiter_deviation (int) : min=0 max=90000 step=10 default=66250 value=66250 flags=slider | |
87 | audio_compression_feature_enabl (bool) : default=1 value=1 | |
88 | audio_compression_gain (int) : min=0 max=20 step=1 default=15 value=15 flags=slider | |
89 | audio_compression_threshold (int) : min=-40 max=0 step=1 default=-40 value=-40 flags=slider | |
90 | audio_compression_attack_time (int) : min=0 max=5000 step=500 default=0 value=0 flags=slider | |
91 | audio_compression_release_time (int) : min=100000 max=1000000 step=100000 default=1000000 value=1000000 flags=slider | |
92 | pilot_tone_feature_enabled (bool) : default=1 value=1 | |
93 | pilot_tone_deviation (int) : min=0 max=90000 step=10 default=6750 value=6750 flags=slider | |
94 | pilot_tone_frequency (int) : min=0 max=19000 step=1 default=19000 value=19000 flags=slider | |
95 | pre_emphasis_settings (menu) : min=0 max=2 default=1 value=1 | |
96 | tune_power_level (int) : min=0 max=120 step=1 default=88 value=88 flags=slider | |
97 | tune_antenna_capacitor (int) : min=0 max=191 step=1 default=0 value=110 flags=slider | |
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98 | |
99 | Here is a summary of them: | |
100 | ||
101 | * Pilot is an audible tone sent by the device. | |
102 | ||
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103 | - pilot_frequency - Configures the frequency of the stereo pilot tone. |
104 | - pilot_deviation - Configures pilot tone frequency deviation level. | |
105 | - pilot_enabled - Enables or disables the pilot tone feature. | |
436e7e7c | 106 | |
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107 | * The si4713 device is capable of applying audio compression to the |
108 | transmitted signal. | |
436e7e7c | 109 | |
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110 | - acomp_enabled - Enables or disables the audio dynamic range control feature. |
111 | - acomp_gain - Sets the gain for audio dynamic range control. | |
112 | - acomp_threshold - Sets the threshold level for audio dynamic range control. | |
113 | - acomp_attack_time - Sets the attack time for audio dynamic range control. | |
114 | - acomp_release_time - Sets the release time for audio dynamic range control. | |
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115 | |
116 | * Limiter setups audio deviation limiter feature. Once a over deviation occurs, | |
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117 | it is possible to adjust the front-end gain of the audio input and always |
118 | prevent over deviation. | |
436e7e7c | 119 | |
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120 | - limiter_enabled - Enables or disables the limiter feature. |
121 | - limiter_deviation - Configures audio frequency deviation level. | |
122 | - limiter_release_time - Sets the limiter release time. | |
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123 | |
124 | * Tuning power | |
125 | ||
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126 | - power_level - Sets the output power level for signal transmission. |
127 | antenna_capacitor - This selects the value of antenna tuning capacitor | |
128 | manually or automatically if set to zero. | |
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129 | |
130 | * RDS related | |
131 | ||
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132 | - rds_ps_name - Sets the RDS ps name field for transmission. |
133 | - rds_radio_text - Sets the RDS radio text for transmission. | |
134 | - rds_pi - Sets the RDS PI field for transmission. | |
135 | - rds_pty - Sets the RDS PTY field for transmission. | |
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136 | |
137 | * Region related | |
138 | ||
b2993570 | 139 | - preemphasis - sets the preemphasis to be applied for transmission. |
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140 | |
141 | RNL | |
b2993570 | 142 | --- |
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143 | |
144 | This device also has an interface to measure received noise level. To do that, you should | |
145 | ioctl the device node. Here is an code of example: | |
146 | ||
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147 | .. code-block:: none |
148 | ||
149 | int main (int argc, char *argv[]) | |
150 | { | |
151 | struct si4713_rnl rnl; | |
152 | int fd = open("/dev/radio0", O_RDWR); | |
153 | int rval; | |
436e7e7c | 154 | |
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155 | if (argc < 2) |
156 | return -EINVAL; | |
436e7e7c | 157 | |
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158 | if (fd < 0) |
159 | return fd; | |
436e7e7c | 160 | |
b2993570 | 161 | sscanf(argv[1], "%d", &rnl.frequency); |
436e7e7c | 162 | |
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163 | rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl); |
164 | if (rval < 0) | |
165 | return rval; | |
436e7e7c | 166 | |
b2993570 | 167 | printf("received noise level: %d\n", rnl.rnl); |
436e7e7c | 168 | |
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169 | close(fd); |
170 | } | |
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171 | |
172 | The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under | |
eb4b0ec7 | 173 | include/linux/platform_data/media/si4713.h. |
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174 | |
175 | Stereo/Mono and RDS subchannels | |
b2993570 | 176 | ------------------------------- |
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177 | |
178 | The device can also be configured using the available sub channels for | |
179 | transmission. To do that use S/G_MODULATOR ioctl and configure txsubchans properly. | |
57f902d0 | 180 | Refer to the V4L2 API specification for proper use of this ioctl. |
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181 | |
182 | Testing | |
b2993570 | 183 | ------- |
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184 | Testing is usually done with v4l2-ctl utility for managing FM tuner cards. |
185 | The tool can be found in v4l-dvb repository under v4l2-apps/util directory. | |
186 | ||
187 | Example for setting rds ps name: | |
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188 | |
189 | .. code-block:: none | |
190 | ||
191 | # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy" | |
436e7e7c | 192 |