Chapter 5: Implementing systems with FPGAs

This chapter dives into the process of designing and implementing systems with FPGAs. It begins with a description of the FPGA compilation software tools that convert a description of a logic design in a programming language into an executable FPGA configuration. We will discuss the types of algorithms best suited to FPGA implementation and suggest a decision approach for determining whether a particular embedded system algorithm is more appropriately implemented using a traditional processor or with an FPGA. The chapter ends with the step-by-step development of a baseline FPGA-based processor project that will be expanded to implement a high-speed digital oscilloscope using circuitry and software developed in later chapters.

After completing this chapter, you will have learned about the processing steps performed by FPGA compilation tools and will understand the types of algorithms best suited to FPGA implementation. You will know how...

Technical requirements

We will be using Xilinx Vivado and an Arty A7-100 development board in this chapter. See Chapter 4, Developing Your First FPGA Program, for information on Vivado download and installation.

The files for this chapter are available at https://github.com/PacktPublishing/Architecting-High-Performance-Embedded-Systems.

The FPGA compilation process

The process of compiling a digital circuit model begins with a specification of circuit behavior in a hardware description language, such as VHDL or Verilog, and produces as its output an implementation of that circuit that can be downloaded and executed in an FPGA. The software tool set that performs the synthesis process is sometimes called a silicon compiler or hardware compiler.

FPGA compilation takes place in three steps: synthesis, placement, and routing. Chapter 4, Developing Your First FPGA Program, introduced these steps. Behind the scenes, the software tools that perform the steps implement a collection of sophisticated algorithms to produce an optimized FPGA configuration that correctly implements the circuit described by the source code.

Before you can begin the compilation process, the first step is to create a complete description of the circuit, typically as a collection of files in the VHDL or Verilog languages. This is called design...

Algorithm types most suitable for FPGA implementation

A key differentiating factor of an algorithm suitable for an FPGA-based solution is that data arrives faster than a standard processor, even a high-speed device, can receive the data, perform the necessary processing, and write output to the intended destination. If this is the case for a particular system architecture, the next question to ask is if there is an available off-the-shelf solution that supports the required data rate and is capable of performing the necessary processing. If no such acceptable solution exists, it is prudent to explore the use of an FPGA in the design. The following sections identify some categories of processing algorithms that often involve the use of FPGAs.

Algorithms that process high-speed data streams

Video is an example of a high-speed data source, with high-resolution video arriving at rates of tens of gigabits per second. If your application involves standard video operations such as signal...

Kicking off the oscilloscope FPGA project

In this section, we will roll up our sleeves and get to work on an FPGA design project that will require the use of the FPGA development process discussed to this point, as well as a high-speed circuit board design, which we will get started on in the next chapter.

Project description

This project will develop a digital oscilloscope based on the Arty A7-100T board that uses a standard oscilloscope probe to measure voltages on a system under test. The key requirements of this project are as follows:

• The input voltage range is ±10V when using a scope probe set to the 1X range.
• The input voltage is sampled at 100 MHz with 14 bits of resolution.
• Input triggering is based on the input signal rising or falling edge and trigger voltage level. Pulse length triggering is also supported.
• Once triggered, up to 248 MB of sequential sample data can be captured. This data will be transferred to the host PC for display after...

Summary

This chapter described the process of designing and implementing systems using FPGAs. It began with a description of the FPGA compilation software tools that convert a description of a logic circuit in an HDL into an executable FPGA configuration. The types of algorithms best suited to FPGAs were identified and a decision approach was proposed for determining whether a particular embedded system algorithm is better suited for execution as code on a traditional processor or in a custom FPGA. The chapter concluded with the development of a complete FPGA-based computer system with TCP/IP networking. This project will be further refined into a high-performance network-connected digital oscilloscope in later chapters.

Having completed this chapter, you learned about the processing performed by FPGA compilation software tools. You understand the types of algorithms most suited to FPGA implementation and how to determine whether FPGA implementation is right for a given application...