PCB
The video decoder daughterboard has a number of BNC connectors for up to 3 input video signals. For this project, we have only used one camera input. The Analog ADV7183A Video Decoder IC is used to decode the analog video signal into an 8-bit digital signal. The output is in the ITU-R BT.656 format. This format uses the YCbCr colour space.
The ADV7183A was chosen because it was readily available (ADV7183B is newer, but more difficult to source) and relatively easy to use. The IC default settings should be sufficient for the project, but can be changed through an I2C compatible bus.
The PCB is designed to plug directly onto our Altera Stratix PCI development board as a daughterboard. A 3.3V supply voltage comes through to the board from the development board. The ADV7183A requires 3.3V and 1.8V supplies. On-board regulators generate the 1.8V supply.
When using an external ATX power supply to power the development board, there needs to be a load resistor across the 5V supply. Without a load on the power supply, there isn't enough current to drive the daughterboard and the Stratix board may be damaged. The daughterboard consumes 300mA at 3.3V (approximately 1W power).
A 27Mhz oscillator provides the ADV7183A with suitable clock signal. The BNC inputs have an impedance of 75 Ohms.
A 10 pin IDC socket has been included to give access to 9 General Purpose I/O (GPIO) pins on the FPGA. Currently we are using this to multiplex two 7-segment displays.