What is a COM Express Module? That is a very good question. On a survey of OEMs that work in the embedded computing industry by people that work in the field, only about 50% know what this module is, while the other half is left in the dark.
With a statistic like that, and when you consider that these modules have been around since 2004, it stands to reason that these COM Express Modules could use an explanation.
A COM Express Module is a form factor of a Computer on Module. Knowing what a Computer on Module (COM for short) is is essential to understanding the COM Express specification. So we’ll touch on that briefly before we get into the meat and potatoes. A COM is just what it says, an entire single board computer built onto a small footprint circuit board. What makes this module different from any other motherboard is that while this module has a processor, RAM slots and I/O controllers, the module doesn’t actually have any I/O. So how the heck is it supposed to work?
The Computer on Module and the Carrier Board
A COM works in conjunction with another board called a “carrier board,” also referred to as a “baseboard.” This board has all of the I/O on it, as well as any other controllers that may be needed that were not included on the COM. Lastly, the carrier board also has a slot in it, which the COM plugs into. Since the carrier board doesn’t have a processor, the COM plus the carrier board essentially makes a complete motherboard.
Consequently, that brings us to the million dollar question. Why would anybody want something like that? The reason for this is customization. If anybody is considering designing a motherboard, then they have one heck of a hill to overcome. The main problem comes in designing the processor and chipsets into the motherboard. If you take these out of the equation, you also take out about 70%-80% of the design work. That is exactly what a COM hopes to achieve. With a COM you can easily design a custom motherboard without having to worry about chipsets and processors, simply by designing a carrier board. In this way you have a board with all of the different I/O and controllers that you would need on a custom motherboard, and can simply plop on a premade COM from an embedded manufacturer. Because different COM form factors follow specific standards, you can even swap out different COMs on the same carrier board in order to make an easily scalable solution.
Benefits of the COM Express Module
When it comes to the COM Express Module, the word is versatility. The specification itself defines 4 different module sizes, ranging from the 55 x 84 mm mini to the 110 x 155 mm extended. In addition to that, there are 7 different pin-outs, the most popular of which is Type 2, simply for its support of both recent and legacy I/O. However, the more recent Type 6 is steadily gaining ground with its support for more recent I/O such as USB 3.0 and a myriad of Digital Display Interfaces.
The last point has little to do with the actual design and specifications of the Com Express Module, but is an important point nonetheless. It has an ease of customization and scalability that surpasses most other COMs simply because it is given wide support by many single board computer manufacturers. Simply as a matter of circumstance, and likely because the specification has been around so long, many manufacturers carry a wide COM Express offering, as well as provide invaluable tools, such as COM Express Development Kits or Starter Kits, in order to help design a carrier board. These come replete with a carrier board with nearly every I/O supported by the COM Express module, design and Gerber files, as well as recourse to FAEs and tech support which will help in your company’s personal design process.
Brian Luckman is the President of New Era Electronics. He has worked in the industrial OEM market for over 25 years, serving a variety of different industries, gaining a strong reputation for his expertise and a thorough understanding of how to properly service OEM customers. In 2000 he began New Era Electronics and the company continues to grow. He’s a husband and father and enjoys exploring the outdoors.
Creative Commons Attribution: Permission is granted to repost this article in its entirety with credit to New Era Electronics and a clickable link back to this page.