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Camera Interface
The OmniVision OVM7690 640x480 CMOS CameraCube provides a digital interface:
DVP[7:0] (Digital video port): 8-bit wide output bus corresponding to pixel information sent
in the selected output format from the OVM7690 (RAW RGB, RGB565, CCIR656, or
YUV422/YCbCr422).
The LRF Module is configured for YUV422 output
http://en.wikipedia.org/wiki/YCbCr). Y is the luma component - brightness in grayscale - and U
and V are chroma components - color differences of blue and red, respectively. The particular
format of YUV422 used by the OVM7690 is known as YUY2 (www.fourcc.org/yuv.php), in which
each 16-bit pixel is given an 8-bit Y component and alternating 8-bit U or 8-bit V component:
Y0U0 corresponds to a single pixel starting from the left, Y1V0 is the 2nd pixel, etc. Every pixel
has Y data, and U and V are every other pixel.
VSYNC (Vertical sync): Indicates the beginning of a new frame by pulsing high.
HREF (Horizontal reference): Indicates the start of the next row of pixels by pulsing high. By
keeping count of the number of HREF pulses received since the last VSYNC, we can determine
which horizontal line of the video frame we are currently on.
PCLK (Pixel clock): Asserted when valid pixel data is available on the DVP bus. For a 640 pixel
line in YUV422 format (16 bits/pixel), 10,240 pixel clock cycles will occur after each HREF pulse.
There are nearly one hundred 8-bit registers within the OVM7690 device that require configuration,
including, but not limited to, general settings, output format selection, resolution, frames per second,
automatic white balance, and gain control. Due to confidentiality concerns, OmniVision does not allow
explicit references or detailed explanations of camera configuration registers. Explanations of group
settings are allowed and provided within the LRF Module source code to give the user an overview of
camera operation. To obtain full OVM7690 product specifications, a non-disclosure agreement (NDA)
must be executed with OmniVision Technologies, Inc. (www.ovt.com).
Copyright © Parallax Inc.
Parallax Laser Range Finder (#28044)
(http://en.wikipedia.org/wiki/YUV
v1.0 9/16/2011 Page 17 of 24
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