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