leds-lm3556.rst

  1========================
  2Kernel driver for lm3556
  3========================
  4
  5* Texas Instrument:
  6  1.5 A Synchronous Boost LED Flash Driver w/ High-Side Current Source
  7* Datasheet: http://www.national.com/ds/LM/LM3556.pdf
  8
  9Authors:
 10      - Daniel Jeong
 11
 12	Contact:Daniel Jeong(daniel.jeong-at-ti.com, gshark.jeong-at-gmail.com)
 13
 14Description
 15-----------
 16There are 3 functions in LM3556, Flash, Torch and Indicator.
 17
 18Flash Mode
 19^^^^^^^^^^
 20
 21In Flash Mode, the LED current source(LED) provides 16 target current levels
 22from 93.75 mA to 1500 mA.The Flash currents are adjusted via the CURRENT
 23CONTROL REGISTER(0x09).Flash mode is activated by the ENABLE REGISTER(0x0A),
 24or by pulling the STROBE pin HIGH.
 25
 26LM3556 Flash can be controlled through /sys/class/leds/flash/brightness file
 27
 28* if STROBE pin is enabled, below example control brightness only, and
 29  ON / OFF will be controlled by STROBE pin.
 30
 31Flash Example:
 32
 33OFF::
 34
 35	#echo 0 > /sys/class/leds/flash/brightness
 36
 3793.75 mA::
 38
 39	#echo 1 > /sys/class/leds/flash/brightness
 40
 41...
 42
 431500  mA::
 44
 45	#echo 16 > /sys/class/leds/flash/brightness
 46
 47Torch Mode
 48^^^^^^^^^^
 49
 50In Torch Mode, the current source(LED) is programmed via the CURRENT CONTROL
 51REGISTER(0x09).Torch Mode is activated by the ENABLE REGISTER(0x0A) or by the
 52hardware TORCH input.
 53
 54LM3556 torch can be controlled through /sys/class/leds/torch/brightness file.
 55* if TORCH pin is enabled, below example control brightness only,
 56and ON / OFF will be controlled by TORCH pin.
 57
 58Torch Example:
 59
 60OFF::
 61
 62	#echo 0 > /sys/class/leds/torch/brightness
 63
 6446.88 mA::
 65
 66	#echo 1 > /sys/class/leds/torch/brightness
 67
 68...
 69
 70375 mA::
 71
 72	#echo 8 > /sys/class/leds/torch/brightness
 73
 74Indicator Mode
 75^^^^^^^^^^^^^^
 76
 77Indicator pattern can be set through /sys/class/leds/indicator/pattern file,
 78and 4 patterns are pre-defined in indicator_pattern array.
 79
 80According to N-lank, Pulse time and N Period values, different pattern wiill
 81be generated.If you want new patterns for your own device, change
 82indicator_pattern array with your own values and INDIC_PATTERN_SIZE.
 83
 84Please refer datasheet for more detail about N-Blank, Pulse time and N Period.
 85
 86Indicator pattern example:
 87
 88pattern 0::
 89
 90	#echo 0 > /sys/class/leds/indicator/pattern
 91
 92...
 93
 94pattern 3::
 95
 96	#echo 3 > /sys/class/leds/indicator/pattern
 97
 98Indicator brightness can be controlled through
 99sys/class/leds/indicator/brightness file.
100
101Example:
102
103OFF::
104
105	#echo 0 > /sys/class/leds/indicator/brightness
106
1075.86 mA::
108
109	#echo 1 > /sys/class/leds/indicator/brightness
110
111...
112
11346.875mA::
114
115	#echo 8 > /sys/class/leds/indicator/brightness
116
117Notes
118-----
119Driver expects it is registered using the i2c_board_info mechanism.
120To register the chip at address 0x63 on specific adapter, set the platform data
121according to include/linux/platform_data/leds-lm3556.h, set the i2c board info
122
123Example::
124
125	static struct i2c_board_info board_i2c_ch4[] __initdata = {
126		{
127			 I2C_BOARD_INFO(LM3556_NAME, 0x63),
128			 .platform_data = &lm3556_pdata,
129		 },
130	};
131
132and register it in the platform init function
133
134Example::
135
136	board_register_i2c_bus(4, 400,
137				board_i2c_ch4, ARRAY_SIZE(board_i2c_ch4));