Reality: The new simulation frontier
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Simulation has its benefits but is not always the best approach when designing highly complex, interconnected electronics devices. By creating FPGA-based systems at the board level, designers can leverage the reconfigurable nature of FPGAs to rapidly develop flexible hardware platforms.
A cartoon shows a father and son in their living room watching a beautiful sunset on television. The kicker is that through the living room window, viewers can see that this sunset is happening right outside.
In electronics, simulation is a useful tool for understanding the workings of the circuits engineers design. But sometimes the drive to simulate obscures the fact that if possible, building and testing the real thing is better than simulating it.
Of course, building and testing the real thing is sometimes difficult, expensive, and time-consuming, which are some of the reasons why simulation was invented in the first place. But electronics technology is changing rapidly, bringing with it new possibilities. Like the father and son in the cartoon, designers just need to look out the window to see it.
Revolutionary technology
From a 21st century perspective, it’s difficult to understand the magnitude of change brought about by microprocessors a couple of decades ago. It wasn’t the processor itself that changed things; rather it allowed functionality to be developed and deployed as software instead of hardwired components. This enabled designers to rapidly develop functionality and implement it without traditional hardware costs. All they needed was memory capacity.
Most engineers acknowledge that the switch to software-based functionality was the catalyst that ignited the whole embedded industry as it is known today. What’s not widely recognized is that another disruptive technology has the potential to significantly influence embedded design: large-scale programmable devices in the form of high-capacity FPGAs.
Although some designers might disagree with this notion on the basis that FPGAs have been around for a while and not yet led to any design revolution, remember that microprocessors hit the scene many years before the embedded industry took off. The key here is critical mass. The processor revolution happened not when the processor was invented, but when it became fast, cheap, and plentiful enough to be used in mainstream applications. FPGAs are now reaching that critical mass.
Today, designers can buy for a few tens of dollars FPGA devices that are fast, feature rich, and have more than enough capacity to house an entire embedded system, processor and all. What’s more, system hardware developed in such a way is as malleable and changeable as traditional C code.
The simulation fixation
So what does this have to do with simulation, and more importantly, what does it mean for design in general?
Until now, low-cost FPGAs have been viewed primarily as a convenient way to consolidate blocks of logic functionality. They’ve been treated as a component of a bigger system. As such, FPGA development has followed the same methodology as chip development. Simulation is a key part of the process.
In much the same way as software developers rely heavily on debuggers and code emulators to track down errors and prove functionality, FPGA designers have grown accustomed to using simulation to develop the functionality they put into chips. Current FPGA design flows are predominantly centered on good simulation tools.
This concept works when developing bits of a system at a low level. But if engineers want go beyond this and capitalize on the potential of using an FPGA as a reconfigurable system platform, they must raise the abstraction level at which they design the interior of the device. Designers must be able to work with large, functional blocks. FPGA-based systems must be created at the board level, not the chip level.
Breadboarding at the nano level
To a board-level designer, the notion of simulating an entire system at the gate level is likely to promote hilarity, if not outright hostility. By assuming that components meet the specs of their data sheets, board-level designers treat components as black boxes and focus development around component interactions. Systems are rarely simulated in their entirety. Instead, they are prototyped and run “live” using test code and/or simulation sources.
And therein lies the beauty of FPGAs. They allow designers to prototype systems to a large extent without having to manufacture the underlying hardware, bringing the mutability of software to the creation of hardware.
Old timers will recognize this paradigm, which used to be called breadboarding. FPGAs take breadboarding to a new level – the nano level (see Figure 1). But they also add a new dimension. Unlike traditional breadboards, the development done on FPGA hardware can translate directly to the finished product. In other words, the development platform and production platform become one and the same.
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Figure 1: Altium’s NanoBoard reconfigurable development platform takes breadboarding to the nano level. Sophisticated controller firmware connects directly to the design software, providing instant system prototyping. (click graphic to zoom by 1.9x) |
From simulation to virtual instrumentation
Large-capacity, feature-rich, low-cost FPGAs have the potential to become the embedded system platform of choice for next-generation electronics products. A few essential keys are needed to unlock this potential.
Chief among these is the creation of design tools that facilitate a component-based approach to FPGA design. Beyond providing a delivery mechanism for the IP blocks necessary to construct an embedded system and a means to connect them together, this new generation of tools must make testing the interconnect signals between logic blocks inside the FPGA possible. Without some method of seeing inside the programmable chip, designers have to rely on simulation to reveal what’s likely to occur. This negates many of the benefits of FPGA-based system design, particularly the rapid design cycle.
FPGA vendors offer some solutions to this problem. Xilinx’s ChipScope, for example, allows designers to incorporate IP that breaks out internal FPGA signals via the JTAG programming port, allowing the status of the signals to be analyzed on a computer.
Altium has taken this concept to another level with a range of configurable virtual instruments supplied as part of Altium Designer (see Figure 2). These instruments are highly configurable and come with sophisticated PC-based dashboards that allow designers to simulate and probe signal lines inside the FPGA in a similar manner to a board-level designer working with bench test instruments.
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Figure 2: Virtual instrumentation supplied as part of Altium Designer lets designers connect to signals and nodes inside an FPGA-based system, allowing them to directly probe, stimulate, control, and test the design’s functionality. (click graphic to zoom by 1.8x) |
Burn and learn
Simulation plays a vital role in electronics design at many levels and will continue to do so. But electronics products today are becoming more complex and increasingly interconnected. The challenge in designing the next generation of electronics devices is finding ways to wrangle this complexity and keep it manageable during development.
FPGAs offer a way forward in that they bring many of the benefits of a software design approach to the creation of system hardware. They allow changes to be made quickly and at no cost, as well as enable hardware functionality to be programmed and altered after manufacture. To harness these benefits, however, designers must abandon their current reliance on simulation in the programmable chip development cycle. This is a crucial step in changing the perception of these devices from a component as a system to the system itself.
If engineers look up from simulation for a moment, they might discover that simply making real hardware will get them to where they want to go more quickly and easily. After all, in the FPGA world, if it doesn’t work the first time, designers can rebuild it in the blink of an eye.
Altium Limited +61-2-8622-8100 rob.irwin@altium.com www.altium.com
