AN2676 Freescale Semiconductor / Motorola, AN2676 Datasheet - Page 8

• Manufacturer Part Number: AN2676
• Description: Image Capture with i.MX21
• Manufacturer: Freescale Semiconductor / Motorola

Image Data Path
7 Image Data Path
7.1 View Finder
The view finder is the most basic application of image capture. An image is taken from the sensor, through
CSI, and is placed in the LCD buffer for display. The input is the sensor, while the output can be a TFT
panel or a smart LCD panel. Depending on the output format of the sensor, several software blocks must be
inserted in between.
The input image is usually a sub-sampled version, or in other cases, resizing is done by the PRP module.
The target output is an RGB565 image placed in a display buffer.
Path 1(Red)—A smart sensor with RGB565 output is used, and, there is no need for resizing. Data is
directly forwarded to the display buffer by DMA. A minimal amount of CPU MIPS is required.
Path 2 (Blue)—A smart sensor with RGB565 output is used, and resizing is required. Data is passed to the
PRP for resizing, then forwarded to the display buffer.
Path 3 (Blue)—A smart sensor with YUV422 output is used. Data is passed to the PRP for color
conversion and resizing, then forwarded to display buffer.
Path 4 (Green)—A dumb sensor with Bayer output and a smart sensor with RGB888 / YUV444 output fall
into this category. Data is passed to a software routine for color processing and color conversion. The
output is fed into the PRP via a frame buffer for resizing, and then forwarded to the display buffer. A
maximum amount of CPU power is consumed.
7.2 Still Capture
In still capture, the image is captured frame by frame. A high quality image is obtained after the whole
chain of color processing, and that image is then converted to YUV420 for JPEG encoding.
The image is captured in full resolution in either YUV422 or RGB565 format. The output from PRP
channel 1 is in RGB565 format, a sub-sampled version for display. The output from PRP channel 2 is in
YUV420 format in full size for JPEG encoding. Both outputs are placed in memory.
8
CSI
Camera
Control
STAT FIFO
Freescale Semiconductor, Inc.
For More Information On This Product,
Buffer
Line
YUV422
RGB565
MC9328MX21 Application Note
RGB565
YUV444
RGB888
Bayer
Go to: www.freescale.com
Figure 6. View Finder
Frame
Buffer
Color
PRP
Proc
RGB565
RGB565
Display
Buffer
SLCDC
LCDC
Memory
MX21 Module
Software
MOTOROLA