FPGA Implementation of Frequency Output and Input Using Handel-C

The use of digital frequency input and output for data transmission remains common in the design of many embedded applications. Conventional methods of frequency generation, based on counting clock cycles, have a precision which is inversely proportional to the frequency to be generated. This paper describes a simple frequency generation technique which, when implemented in low-cost FPGA hardware, provides a precision of 5 × 10^-6% or better for all frequencies. The method represents an intermediate non-available frequency by dithering between two exact frequencies. Laboratory measurements show that, averaged over 2s, the desired frequency is generated to the required precision. This application is used to illustrate the high level of abstraction in the Handel-C language for describing FPGA functionality.