The TWL system includes two cameras. Although cameras can be controlled separately, it is not possible to obtain images from both cameras simultaneously.
The camera library cannot be used in CODEC-DS mode. Always use CODEC-TWL mode.
Use the API to control camera operations.
The basic camera specifications are listed below.
Of these, the resolution, effect, and flipping are handled in two contexts for each camera. It can be faster to switch contexts than to set these separately.
The library automatically puts the cameras in standby mode when the hardware is reset or put to sleep. To enable the camera after recovering from sleep, the application must implement the process.
Contexts handle the following default values when the cameras are started (when the CAMERA_Init function is called).
Inner Camera: Context A
| Resolution | CAMERA_SIZE_DS_LCD |
| Effect | CAMERA_EFFECT_NONE |
| Flipping | CAMERA_FLIP_HORIZONTAL |
Inner Camera: Context B
| Resolution | CAMERA_SIZE_VGA |
| Effect | CAMERA_EFFECT_NONE |
| Flipping | CAMERA_FLIP_HORIZONTAL |
Outer Camera: Context A
| Resolution | CAMERA_SIZE_DS_LCD |
| Effect | CAMERA_EFFECT_NONE |
| Flipping | CAMERA_FLIP_NONE |
Outer Camera: Context B
| Resolution | CAMERA_SIZE_VGA |
| Effect | CAMERA_EFFECT_NONE |
| Flipping | CAMERA_FLIP_NONE |
By default, both the inner and outer cameras are in context A.
Contexts do not handle the following default values.
Inner Camera
| Frame rate | CAMERA_FRAME_RATE_15 |
| Photo mode | CAMERA_PHOTO_MODE_PORTRAIT |
Outer Camera
| Frame rate | CAMERA_FRAME_RATE_15 |
| Photo mode | CAMERA_PHOTO_MODE_NORMAL |
| Output Format | CAMERA_OUTPUT_YUV |
| Number of Lines to Transfer | 1 line |
See the links for specific descriptions of the parameter meanings.
The camera gets image data in the YCrYCb (YUV4:2:2) format or the RGB (RGB5:5:5) format.
YUV422 is converted into RGB8:8:8 as follows.
R = 1.000 x Y + 1.402 x (V - 128) G = 1.000 x Y - 0.344 x (U - 128) - 0.714 x (V - 128) B = 1.000 x Y + 1.772 x (U - 128)
The results of the calculation will be rounded off if they are less than 0 or exceed 255. Then they will be scaled to the range [0–31], after which they will be in RGB555 format.
The formulas for the reverse conversion (i.e., converting RGB555 to YUV422) are shown below:
Y = 0.299 x R + 0.587 x G + 0.114 x B U = -0.169 x R - 0.331 x G + 0.500 x B + 128 V = 0.500 x R - 0.419 x G - 0.081 x B + 128
2008/10/06 Described camera library CODEC mode restrictions.
2008/09/11 Added a description of initial values of the camera.
2008/04/21 Added shooting mode for initial values of camera settings.
2008/03/17 Added a description of operations during hardware reset and during sleep mode.
2007/11/14 Initial version.
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