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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. | |
57f902d0 | 167 | Refer to the V4L2 API specification for proper use of this ioctl. |
436e7e7c EV |
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 |