Chapter 12
Interfacing
An image processing system never stands alone. This is particularly the case for an embedded vision system, which is usually designed for one specific purpose or task. Therefore, there are usually one or more peripheral devices connected to the FPGA implementing the system.
Each device connected to the FPGA must have an appropriate interface within the FPGA. This is responsible for passing any data to or from the rest of the logic, including any format conversions required between the peripheral and the processor implementing the algorithm within the FPGA. It is also responsible for providing any control signals required by the peripheral device. This may range from a clock signal and simple handshaking through to complex protocol management. Many peripheral devices require initialisation or configuration through the setting of control registers.
The interface logic may be thought of as a device driver, shielding the image processing hardware from much of the lower level complexities of the physical interface (Bailey et al., 2006). The primary focus of this chapter is on some of the techniques associated with the design of such interfaces. The term device driver may be a little misleading in this context, as it is referring primarily to interface hardware. If the system is made of a mix of programmable hardware and software, then the interface between them will also be in the form of a software device driver (Williams, 2009).
It is also useful within this ...
