linux/Documentation/video4linux/cpia2_overview.txt
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   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.
  39
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