| Alan Cox | ab33d50 | 2006-02-27 00:09:05 -0300 | [diff] [blame] | 1 | Programmer's View of Cpia2 |
| 2 | |
| 3 | Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a |
| 4 | division of ST Microelectronics). There are two versions. The first is the |
| 5 | STV0672, which is capable of up to 30 frames per second (fps) in frame sizes |
| 6 | up to CIF, and 15 fps for VGA frames. The STV0676 is an improved version, |
| 7 | which can handle up to 30 fps VGA. Both coprocessors can be attached to two |
| 8 | CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor. These will |
| 9 | be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors. |
| 10 | |
| 11 | The two chipsets operate almost identically. The core is an 8051 processor, |
| 12 | running two different versions of firmware. The 672 runs the VP4 video |
| 13 | processor code, the 676 runs VP5. There are a few differences in register |
| 14 | mappings for the two chips. In these cases, the symbols defined in the |
| 15 | header files are marked with VP4 or VP5 as part of the symbol name. |
| 16 | |
| 17 | The cameras appear externally as three sets of registers. Setting register |
| 18 | values is the only way to control the camera. Some settings are |
| 19 | interdependant, such as the sequence required to power up the camera. I will |
| 20 | try to make note of all of these cases. |
| 21 | |
| 22 | The register sets are called blocks. Block 0 is the system block. This |
| 23 | section is always powered on when the camera is plugged in. It contains |
| 24 | registers that control housekeeping functions such as powering up the video |
| 25 | processor. The video processor is the VP block. These registers control |
| 26 | how the video from the sensor is processed. Examples are timing registers, |
| 27 | user mode (vga, qvga), scaling, cropping, framerates, and so on. The last |
| 28 | block is the video compressor (VC). The video stream sent from the camera is |
| 29 | compressed as Motion JPEG (JPEGA). The VC controls all of the compression |
| 30 | parameters. Looking at the file cpia2_registers.h, you can get a full view |
| 31 | of these registers and the possible values for most of them. |
| 32 | |
| 33 | One or more registers can be set or read by sending a usb control message to |
| 34 | the camera. There are three modes for this. Block mode requests a number |
| 35 | of contiguous registers. Random mode reads or writes random registers with |
| 36 | a tuple structure containing address/value pairs. The repeat mode is only |
| 37 | used by VP4 to load a firmware patch. It contains a starting address and |
| 38 | a sequence of bytes to be written into a gpio port. |