Standard versus custom? Choose both

The decision to use standard products or design a custom board for your application involves many factors. Volume, development cost, production cost, product life cycle, and reliability are typically key considerations. The three options are: full custom boards, standard boards, or a combination of both.

Designing a full custom board for your application will result in a board that does exactly what you want. You won’t have to pay for features you don’t need, but any change in requirements will result in re-layout. The development cost is high, but the recurring cost is typically low. If the technology or your requirements change, you have to redo the entire board. If the quantity is very large, it’s not a problem. This technique is used in many commercial applications such as cell phones, laptop computers, and in-car GPS systems.

Using small form factor boards based on a standard, whether it is the PC/104 family, a Computer-On-Module (COM)/COM Express variant, MicroTCA, 3U CompactPCI, or VPX, reduces your dependence on a single supplier. There are lots of boards to choose from at very competitive prices. If someone makes a board or stack of boards that covers your application requirements, then you have a quick way to configure your system. However, there are limitations in that everything you need might not be available in that form factor, or you might need to build the rest of the system if the form factor only provides the computing engine.

PC/104 works very well in this approach. Its standard PC architecture – with ISA, PCI, and PCI Express buses and hundreds of vendors that make nearly everything you can imagine in three different form factors – suits many applications. Standardization means that boards from different vendors play together nicely. Having a large number of suppliers ensures that designers will find what they need. There are also many enclosure selections available, from inexpensive extruded aluminum to rugged frames milled from a solid aluminum block. PC/104 is inherently rugged and has been proven in many demanding applications.

A combination system requires building a custom baseboard to do the special things the application requires, things not offered on standard products. This could include analog I/O, motor controllers, relays, fiber-optic interfaces, GPS, custom FPGAs, and cellular modems. The CPU is added via a standard interface. This board becomes the brains of the system and can be easily upgraded as technology advances and processing requirements change.

While this method is typically applied to mezzanine processor cards such as COM/COM Express, PC/104’s stacking ability makes it a strong contender for these applications (see Figure 1). Putting a PC/104 ISA, PCI, or PCI Express connector on the baseboard opens up a wealth of CPU options. An additional advantage is that the system can change or expand simply by introducing an additional PC/104 board. So when the boss says that the system needs a Wi-Fi interface or cellular modem and GPS, the answer is easy: Just add another PC/104 board. Think of PC/104 as a standard board for your custom system.

Figure 1: Putting the PC/104 form factor on a larger board, such as this EBX SBC with a PC/104-Plus module installed, creates more CPU options in mezzanine applications.

Using standards-based components can thus simplify the decision of choosing the correct architecture for an embedded system. PC/104 offers multiple PC bus structures, three form factors, and a broad product offering supported by many different manufacturers. It gives designers the ability to use standard modules and still get a custom system.

The PC/104 Consortium’s website product page at lists nearly 500 products from 59 companies, and this is just a limited sample from members only. PC/104 is both a mezzanine component and a complete stackable PC system, making the question of standard versus custom much easier to answer.

PC/104 Consortium 916-270-2016