leds-trigger-pattern.txt (2008B)
1* Pattern format for LED pattern trigger 2 3The pattern is given by a series of tuples, of brightness and duration (ms). 4The LED is expected to traverse the series and each brightness value for the 5specified duration. Duration of 0 means brightness should immediately change to 6new value, and writing malformed pattern deactivates any active one. 7 81. For gradual dimming, the dimming interval now is set as 50 milliseconds. So 9the tuple with duration less than dimming interval (50ms) is treated as a step 10change of brightness, i.e. the subsequent brightness will be applied without 11adding intervening dimming intervals. 12 13The gradual dimming format of the software pattern values should be: 14"brightness_1 duration_1 brightness_2 duration_2 brightness_3 duration_3 ...". 15For example (using sysfs interface): 16 17echo 0 1000 255 2000 > pattern 18 19It will make the LED go gradually from zero-intensity to max (255) intensity in 201000 milliseconds, then back to zero intensity in 2000 milliseconds: 21 22LED brightness 23 ^ 24255-| / \ / \ / 25 | / \ / \ / 26 | / \ / \ / 27 | / \ / \ / 28 0-| / \/ \/ 29 +---0----1----2----3----4----5----6------------> time (s) 30 312. To make the LED go instantly from one brightness value to another, we should 32use zero-time lengths (the brightness must be same as the previous tuple's). So 33the format should be: "brightness_1 duration_1 brightness_1 0 brightness_2 34duration_2 brightness_2 0 ...". 35For example (using sysfs interface): 36 37echo 0 1000 0 0 255 2000 255 0 > pattern 38 39It will make the LED stay off for one second, then stay at max brightness for 40two seconds: 41 42LED brightness 43 ^ 44255-| +---------+ +---------+ 45 | | | | | 46 | | | | | 47 | | | | | 48 0-| -----+ +----+ +---- 49 +---0----1----2----3----4----5----6------------> time (s)