Nokia N900 Service Manual

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There are also a few keys/switches that are not in the keyboard matrix but are instead connected to OMAP’sGPIO pins. These are side keys that are volume/zoom keys and dual action camera key, where the first stageis used for auto focus function and when the key is pressed completely it acts as a shutter key.CamerasRX-51 camera concept has two cameras. A 5 megapixel main camera for still and video imaging and a VGAresolution front camera for video calls. Both cameras use dedicated CCP2 differential camera interface. OMAPhas only one CCP2 port so the CCP-lines are multiplexed with switches.The device has also a camera flash located directly beside the main camera, providing better image qualityin darker environments. The flash has a built-in red indicator that is used as a privacy indicator. The red ledis lit during video recording and it is also used to indicate image capture with the main camera.IlluminationThe Qwerty keyboard is backlit with 6 LEDs. The power supply for the LEDs is called Lysti which is a 9-channelLED controller. It also controls and supplies the RGB LED in the upper block. It can control all 9-channelsindividually.SensorsThe device has several sensors.Battery cover sensorBattery cover sensor is a hall sensor that recognizes magnet that is inside the battery cover. It is used toprotect memory cards from battery removal. It also enables hot swapping of the memory card.Slide sensorSlide sensor is an MR sensor which also uses magnets for state switching. In this device it is used to detectthe slide movement that reveals the qwerty keyboard.Camera door sensorCamera door has an optical sensor that detects when it is opened. It is used to automatically open the cameraapplication when the main camera is revealed. Its operation is based on detecting the reflecting IR light fromits transmitter to its receiver.Proximity sensorProximity sensor is basically the same kind of optical sensor as the camera door sensor but its operatingrange is slightly longer. It is used to lock the touch screen when the device is near the head during phonecalls so that there are no accidental touch interactions from the cheek etc.AccelerometerThe device also employs a 3D-accelerometer that can detect acceleration on all 3 axis. It is used for exampleto detect the device's position when images are taken with camera or to turn the UI with certain applications.Ambient light sensor (ALS)Ambient light sensor is used to detect surrounding light levels. Its readings are used to adjust keyboard lightand display backlight levels. So in bright surroundings the keyboard is turned off and display is made brighterfor better readability, and in dark the display is dimmed and keyboard lights are turned on.RX-51System ModuleIssue 1 COMPANY CONFIDENTIAL Page 6 –17Copyright © 2009 Nokia. All rights reserved.