1 .. SPDX-License-Identifier: GPL-2.0
2
3 .. include:: <isonum.txt>
4
5 The Silicon Labs Si4713 FM Radio Transmitter Driver
6 ===================================================
7
8 Copyright |copy| 2009 Nokia Corporation
9
10 Contact: Eduardo Valentin <eduardo.valentin@nokia.com>
11
12
13 Information about the Device
14 ----------------------------
15
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
29 -------------------------
30
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
48 ----------------------
49
50 The properties can be accessed using v4l2 extended controls.
51 Here is an output from v4l2-ctl util:
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
98
99 Here is a summary of them:
100
101 * Pilot is an audible tone sent by the device.
102
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.
106
107 * The si4713 device is capable of applying audio compression to the
108 transmitted signal.
109
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.
115
116 * Limiter setups audio deviation limiter feature. Once a over deviation occurs,
117 it is possible to adjust the front-end gain of the audio input and always
118 prevent over deviation.
119
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.
123
124 * Tuning power
125
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.
129
130 * RDS related
131
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.
136
137 * Region related
138
139 - preemphasis - sets the preemphasis to be applied for transmission.
140
141 RNL
142 ---
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
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;
154
155 if (argc < 2)
156 return -EINVAL;
157
158 if (fd < 0)
159 return fd;
160
161 sscanf(argv[1], "%d", &rnl.frequency);
162
163 rval = ioctl(fd, SI4713_IOC_MEASURE_RNL, &rnl);
164 if (rval < 0)
165 return rval;
166
167 printf("received noise level: %d\n", rnl.rnl);
168
169 close(fd);
170 }
171
172 The struct si4713_rnl and SI4713_IOC_MEASURE_RNL are defined under
173 include/linux/platform_data/media/si4713.h.
174
175 Stereo/Mono and RDS subchannels
176 -------------------------------
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.
180 Refer to the V4L2 API specification for proper use of this ioctl.
181
182 Testing
183 -------
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:
188
189 .. code-block:: none
190
191 # v4l2-ctl -d /dev/radio0 --set-ctrl=rds_ps_name="Dummy"
192
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