Root/Documentation/video4linux/cpia2_overview.txt

1            Programmer's View of Cpia2
2
3Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a
4division of ST Microelectronics). There are two versions. The first is the
5STV0672, which is capable of up to 30 frames per second (fps) in frame sizes
6up to CIF, and 15 fps for VGA frames. The STV0676 is an improved version,
7which can handle up to 30 fps VGA. Both coprocessors can be attached to two
8CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor. These will
9be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors.
10
11The two chipsets operate almost identically. The core is an 8051 processor,
12running two different versions of firmware. The 672 runs the VP4 video
13processor code, the 676 runs VP5. There are a few differences in register
14mappings for the two chips. In these cases, the symbols defined in the
15header files are marked with VP4 or VP5 as part of the symbol name.
16
17The cameras appear externally as three sets of registers. Setting register
18values is the only way to control the camera. Some settings are
19interdependant, such as the sequence required to power up the camera. I will
20try to make note of all of these cases.
21
22The register sets are called blocks. Block 0 is the system block. This
23section is always powered on when the camera is plugged in. It contains
24registers that control housekeeping functions such as powering up the video
25processor. The video processor is the VP block. These registers control
26how the video from the sensor is processed. Examples are timing registers,
27user mode (vga, qvga), scaling, cropping, framerates, and so on. The last
28block is the video compressor (VC). The video stream sent from the camera is
29compressed as Motion JPEG (JPEGA). The VC controls all of the compression
30parameters. Looking at the file cpia2_registers.h, you can get a full view
31of these registers and the possible values for most of them.
32
33One or more registers can be set or read by sending a usb control message to
34the camera. There are three modes for this. Block mode requests a number
35of contiguous registers. Random mode reads or writes random registers with
36a tuple structure containing address/value pairs. The repeat mode is only
37used by VP4 to load a firmware patch. It contains a starting address and
38a sequence of bytes to be written into a gpio port.

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