N900 Hardware LED
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In order for the LEDs to work, the led_current of the appropriate LEDs need to be set to non-zero values. This is accomplished by writing to files LEDs:lp5523:[bgr]/led_current under the same directory. Perhaps (?) not or values are suitable. | In order for the LEDs to work, the led_current of the appropriate LEDs need to be set to non-zero values. This is accomplished by writing to files LEDs:lp5523:[bgr]/led_current under the same directory. Perhaps (?) not or values are suitable. | ||
| + | |||
| + | Despite the line | ||
| + | <pre> | ||
| + | 87 #define LP5523_DEFAULT_CURRENT 50 /* microAmps */ | ||
| + | </pre> suggesting different, the units in there are 0.1mA. So the drivir init default for all LED is 5mA, and mce seems to set current to 0.2mA (value 2 in the led_current sysnode) for B and G, and either to 0.2mA or 0.8mA for R. Probably settings as high as 100 for 10mA are safe for the RGB LED, higher values might destroy the LED. | ||
NOTE: There must be a delay (how much? The specs of LP5521 mentions it) between writes to sysfs files. | NOTE: There must be a delay (how much? The specs of LP5521 mentions it) between writes to sysfs files. | ||
Revision as of 15:13, 28 July 2010
Hardware
The N900 has a LP5521[1] [2] programmable three channel controller LED Driver which handles the keyboard and notification LED. (not the flash LEDs and red indicator light next to those, and also not the Infrared-LED used for CIR) (actually it has a LP5523 [3] [4], which has 3 engines like LP5521 but can drive 9 LEDs via a multiplexer which maps each LED to one of the 3 engines. A LED also can be unassigned to any engine, in which case you can control it by writing to the corresponding brightness sysnode)
The controller can be programmed via "/sys/class/i2c-adapter/i2c-2/2-0032" (FIXME: is this stable?). In that directory there are three files corresponding to the three channels: engine1_mode, engine2_mode and engine3_mode. Each file "stores" one of "run", "load", "disabled" (it seems that there is another mode "direct" but it doesn't work):
- run: The program runs
- disabled: The channel is disabled - not running
- load: In that state, there are two more files in that directory:
- engine1_LEDs is in the form "0000rgb00" (9 digits, "1" or "0"), where rgb control which LEDs should participate. The 6 "0" in the above pattern correspond to the 6 kbd white LEDs controlled by MCE via engine3, so readout of engine3_leds gives 111100011 ;-)
- engine1_load accepts a string as specified above (e.g. 9d804000427f0d7f7f007f0042000000). LP5523 has an absolute storage of 96 steps a 16bits, which can dynamically partitioned between the three engines. (ToDo: check if driver supports >16 instructions / machine)
After that, when the state is changed to "run", the program will be ran by the controller.
In order for the LEDs to work, the led_current of the appropriate LEDs need to be set to non-zero values. This is accomplished by writing to files LEDs:lp5523:[bgr]/led_current under the same directory. Perhaps (?) not or values are suitable.
Despite the line
87 #define LP5523_DEFAULT_CURRENT 50 /* microAmps */suggesting different, the units in there are 0.1mA. So the drivir init default for all LED is 5mA, and mce seems to set current to 0.2mA (value 2 in the led_current sysnode) for B and G, and either to 0.2mA or 0.8mA for R. Probably settings as high as 100 for 10mA are safe for the RGB LED, higher values might destroy the LED.
NOTE: There must be a delay (how much? The specs of LP5521 mentions it) between writes to sysfs files.