Cameras; Illumination; Sensors; Proximity Sensor - Nokia N900 Service Manual

RX-51
System Module
There are also a few keys/switches that are not in the keyboard matrix but are instead connected to OMAP's
GPIO pins. These are side keys that are volume/zoom keys and dual action camera key, where the first stage
is used for auto focus function and when the key is pressed completely it acts as a shutter key.

Cameras

RX-51 camera concept has two cameras. A 5 megapixel main camera for still and video imaging and a VGA
resolution front camera for video calls. Both cameras use dedicated CCP2 differential camera interface. OMAP
has 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 quality
in darker environments. The flash has a built-in red indicator that is used as a privacy indicator. The red led
is lit during video recording and it is also used to indicate image capture with the main camera.

Illumination

The Qwerty keyboard is backlit with 6 LEDs. The power supply for the LEDs is called Lysti which is a 9-channel
LED controller. It also controls and supplies the RGB LED in the upper block. It can control all 9-channels
individually.

Sensors

The device has several sensors.
Battery cover sensor
Battery cover sensor is a hall sensor that recognizes magnet that is inside the battery cover. It is used to
protect memory cards from battery removal. It also enables hot swapping of the memory card.
Slide sensor
Slide sensor is an MR sensor which also uses magnets for state switching. In this device it is used to detect
the slide movement that reveals the qwerty keyboard.
Camera door sensor
Camera door has an optical sensor that detects when it is opened. It is used to automatically open the camera
application when the main camera is revealed. Its operation is based on detecting the reflecting IR light from
its transmitter to its receiver.

Proximity sensor

Proximity sensor is basically the same kind of optical sensor as the camera door sensor but its operating
range is slightly longer. It is used to lock the touch screen when the device is near the head during phone
calls so that there are no accidental touch interactions from the cheek etc.
Accelerometer
The device also employs a 3D-accelerometer that can detect acceleration on all 3 axis. It is used for example
to 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 light
and display backlight levels. So in bright surroundings the keyboard is turned off and display is made brighter
for better readability, and in dark the display is dimmed and keyboard lights are turned on.
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