Android Lights

Android defines a user space C abstraction interface for LED hardware. The interface header is defined inhardware/libhardware/include/hardware/lights.h. In order to integrate LEDs with Android you need to build a shared library that implements this interface. The types of logical lights currently supported by Android include:

• Backlight
• Keyboard
• Buttons
• Battery
• Notifications
• Attention

 

Building a Lights Library

To implement a Lights driver, create a shared library that implements the interface defined in lights.h. You must name your shared library liblights.so so that it will get loaded from /system/libat runtime.

Interface

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lights.h File Reference

Data Structures

struct  light_device_

tstruct  light_state_t 

The parameters that can be set for a given light. More...

 

00001 /*
00002  * Copyright (C) 2008 The Android Open Source Project
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *      http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef ANDROID_LIGHTS_INTERFACE_H
00018 #define ANDROID_LIGHTS_INTERFACE_H
00019 
00020 #include <stdint.h>
00021 #include <sys/cdefs.h>
00022 #include <sys/types.h>
00023 
00024 #include <hardware/hardware.h>
00025 
00026 __BEGIN_DECLS
00027 
00028 /**
00029  * The id of this module
00030  */
00031 #define LIGHTS_HARDWARE_MODULE_ID "lights"
00032 
00033 /*
00034  * These light IDs correspond to logical lights, not physical.
00035  * So for example, if your INDICATOR light is in line with your
00036  * BUTTONS, it might make sense to also light the INDICATOR
00037  * light to a reasonable color when the BUTTONS are lit.
00038  */
00039 #define LIGHT_ID_BACKLIGHT          "backlight"
00040 #define LIGHT_ID_KEYBOARD           "keyboard"
00041 #define LIGHT_ID_BUTTONS            "buttons"
00042 #define LIGHT_ID_BATTERY            "battery"
00043 #define LIGHT_ID_NOTIFICATIONS      "notifications"
00044 #define LIGHT_ID_ATTENTION          "attention"
00045 
00046 /*
00047  * These lights aren't currently supported by the higher
00048  * layers, but could be someday, so we have the constants
00049  * here now.
00050  */
00051 #define LIGHT_ID_BLUETOOTH          "bluetooth"
00052 #define LIGHT_ID_WIFI               "wifi"
00053 
00054 /* ************************************************************************
00055  * Flash modes for the flashMode field of light_state_t.
00056  */
00057 
00058 #define LIGHT_FLASH_NONE            0
00059 
00060 /**
00061  * To flash the light at a given rate, set flashMode to LIGHT_FLASH_TIMED,
00062  * and then flashOnMS should be set to the number of milliseconds to turn
00063  * the light on, followed by the number of milliseconds to turn the light
00064  * off.
00065  */
00066 #define LIGHT_FLASH_TIMED           1
00067 
00068 /**
00069  * To flash the light using hardware assist, set flashMode to
00070  * the hardware mode.
00071  */
00072 #define LIGHT_FLASH_HARDWARE        2
00073 
00074 /**
00075  * Light brightness is managed by a user setting.
00076  */
00077 #define BRIGHTNESS_MODE_USER        0
00078 
00079 /**
00080  * Light brightness is managed by a light sensor.
00081  */
00082 #define BRIGHTNESS_MODE_SENSOR      1
00083 
00084 /**
00085  * The parameters that can be set for a given light.
00086  *
00087  * Not all lights must support all parameters.  If you
00088  * can do something backward-compatible, you should.
00089  */
00090 struct light_state_t {
00091     /**
00092      * The color of the LED in ARGB.
00093      *
00094      * Do your best here.
00095      *   - If your light can only do red or green, if they ask for blue,
00096      *     you should do green.
00097      *   - If you can only do a brightness ramp, then use this formula:
00098      *      unsigned char brightness = ((77*((color>>16)&0x00ff))
00099      *              + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8;
00100      *   - If you can only do on or off, 0 is off, anything else is on.
00101      *
00102      * The high byte should be ignored.  Callers will set it to 0xff (which
00103      * would correspond to 255 alpha).
00104      */
00105     unsigned int color;
00106 
00107     /**
00108      * See the LIGHT_FLASH_* constants
00109      */
00110     int flashMode;
00111     int flashOnMS;
00112     int flashOffMS;
00113 
00114     /**
00115      * Policy used by the framework to manage the light's brightness.
00116      * Currently the values are BRIGHTNESS_MODE_USER and BRIGHTNESS_MODE_SENSOR.
00117      */
00118     int brightnessMode;
00119 };
00120 
00121 struct light_device_t {
00122     struct hw_device_t common;
00123 
00124     /**
00125      * Set the provided lights to the provided values.
00126      *
00127      * Returns: 0 on succes, error code on failure.
00128      */
00129     int (*set_light)(struct light_device_t* dev,
00130             struct light_state_t const* state);
00131 };
00132 
00133 
00134 __END_DECLS
00135 
00136 #endif  // ANDROID_LIGHTS_INTERFACE_H
00137

原文：http://source.android.com/porting/lights.html