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Kernel driver for lm3556
* Texas Instrument:
1.5 A Synchronous Boost LED Flash Driver w/ High-Side Current Source
* Datasheet:
- Daniel Jeong
Contact:Daniel Jeong(,
There are 3 functions in LM3556, Flash, Torch and Indicator.
Flash Mode
In Flash Mode, the LED current source(LED) provides 16 target current levels
from 93.75 mA to 1500 mA.The Flash currents are adjusted via the CURRENT
CONTROL REGISTER(0x09).Flash mode is activated by the ENABLE REGISTER(0x0A),
or by pulling the STROBE pin HIGH.
LM3556 Flash can be controlled through /sys/class/leds/flash/brightness file
* if STROBE pin is enabled, below example control brightness only, and
ON / OFF will be controlled by STROBE pin.
Flash Example:
#echo 0 > /sys/class/leds/flash/brightness
93.75 mA::
#echo 1 > /sys/class/leds/flash/brightness
1500 mA::
#echo 16 > /sys/class/leds/flash/brightness
Torch Mode
In Torch Mode, the current source(LED) is programmed via the CURRENT CONTROL
REGISTER(0x09).Torch Mode is activated by the ENABLE REGISTER(0x0A) or by the
hardware TORCH input.
LM3556 torch can be controlled through /sys/class/leds/torch/brightness file.
* if TORCH pin is enabled, below example control brightness only,
and ON / OFF will be controlled by TORCH pin.
Torch Example:
#echo 0 > /sys/class/leds/torch/brightness
46.88 mA::
#echo 1 > /sys/class/leds/torch/brightness
375 mA::
#echo 8 > /sys/class/leds/torch/brightness
Indicator Mode
Indicator pattern can be set through /sys/class/leds/indicator/pattern file,
and 4 patterns are pre-defined in indicator_pattern array.
According to N-lank, Pulse time and N Period values, different pattern wiill
be generated.If you want new patterns for your own device, change
indicator_pattern array with your own values and INDIC_PATTERN_SIZE.
Please refer datasheet for more detail about N-Blank, Pulse time and N Period.
Indicator pattern example:
pattern 0::
#echo 0 > /sys/class/leds/indicator/pattern
pattern 3::
#echo 3 > /sys/class/leds/indicator/pattern
Indicator brightness can be controlled through
sys/class/leds/indicator/brightness file.
#echo 0 > /sys/class/leds/indicator/brightness
5.86 mA::
#echo 1 > /sys/class/leds/indicator/brightness
#echo 8 > /sys/class/leds/indicator/brightness
Driver expects it is registered using the i2c_board_info mechanism.
To register the chip at address 0x63 on specific adapter, set the platform data
according to include/linux/platform_data/leds-lm3556.h, set the i2c board info
static struct i2c_board_info board_i2c_ch4[] __initdata = {
I2C_BOARD_INFO(LM3556_NAME, 0x63),
.platform_data = &lm3556_pdata,
and register it in the platform init function
board_register_i2c_bus(4, 400,
board_i2c_ch4, ARRAY_SIZE(board_i2c_ch4));