Computer On Modules – or Mezzanine modules, have existed in different guises almost as long as board level products have been in existence. PMC modules, IndustryPacks, PC/104, ETX, Com Express, QSeven to name but a few. It is the reasoning behind the choice of modules that has changed over the years. The selection of a PMC module to provide say a serial interface controller will speed up the design process because it is the only practical choice. With the advent of the advanced Computer on Module such as COM Express or QSeven, the system designer can now overcome a number of issues. For example, if he tries to design the full PC from scratch using a conventional process, a number of difficulties present themselves. First the technology tends to be a closely guarded secret unless you’re one of the major PC manufacturers signed up to all the latest NDA requirements and well connected with the manufacturers applications, engineers data is difficult to obtain. Following closely is component availability. Small volumes of state of the art chips can be difficult to come by and by small I mean a few hundred pieces.
As if that wasn’t enough, modern PCs need a BIOS of some description with the inherent high cost of entry to get started. This needs licensing and has its own set of skills required to get is running and then maintain.
So designing in a module where someone else takes care of all this makes good engineering and commercial sense.
You design a baseboard to take the module of choice and design all the interfaces you require for real world connectivity. Be they an LCD screen, IEEE1394, special bit twiddler for control of your machine, or those industry specific connectors which you are obliged to use. It is up to you. With the well publicised specifications for most modules readily available it will be easy to keep your product up to date by updating the mezzanine.
Not necessarily so.
The reason you selected the module was because it offered the facilities you needed. If you change the module the CPU and chipset are going to change. As likely as not so are the peripherals and the software.
A Computer on Module is best to be considered as a component in the baseboard or system design. Treat it as you would a complex chip. If you manage to upgrade by changing the module consider it a bonus not a certainty. Best then to treat the Computer on Modules as a means to speed time to market and circumvent the many obstacles that would otherwise present themselves if you try to design everything from scratch.
Click to view our selection of modules below: