I am regularly in the situation where the choice of processor, module and thus vendor selection is still a customer question. This should not be a great surprise as there are so many variants for consideration. So I’ll try and help with my thought process and highlight the major considerations when making this selection.
Obviously the overall technical decision comes from the functional requirements, but also for what is it going to be used for?
Most development projects are not fixed to a single function. More and more companies require the use of the platform as the foundation for the product range going forward. It then becomes a fine balance of processor power, functional components and cost.
With software execution and data processing normally at the core of the whole system, choice is affected by architecture and instruction set (ARM9, Cortex-A8 or Cortex-A9). Also how fast the ARM core runs, and compiler optimization availability in the software build (Linux, Android, Windows CE 6.0 and Compact 7). So to select from this range you should consider the need to process the data onboard or transfer data at high speed. If neither of these is a priority then a lower specification core and speed of module could be selected. The other main consideration is the graphics requirement. If you simply want a 2D/flat user interface without animations it can make a huge difference to the selection, as a standard LCD controller would be sufficient. Otherwise you will need a Graphics Processing Unit (GPU) which generally only come fitted in the higher end processor designs e.g. Cortex-Ax series. Once you have cleared these two questions it really narrows the choice and allows you to focus on the more functional areas of the selection (USB, Ethernet, SPI, I2C etc.)
Most vertical market product business is based on the ability to supply the design for many years, with 5 to 10 generally accepted. Plus, in this market the testing and maybe product certification process can be worth more than its development, so consistency of supply is paramount. To answer this and select the right SOM you should ask and look for history of supply, and if required an additional statement of longevity. The SOM manufacturer’s selection of its silicon vendors is a main parameter in this, with specifically Freescale and Texas Instrument being the leading specialists quoting 10 to 15 years for their parts.
Even though this is not a physical item delivered with the SOM. I believe it is an important part of the selection process. So things to look for when making your selection are:-
Can you speak with someone rather than just email? Much information and help can be dynamically supplied if you can work through your thoughts with an engineer. Does the vendor supply ongoing updates and help? If the software and BSP is truly production ready there will be updates and not just the Silicon Vendor software download from day one. Can you get help for addition tasks and review your design? The supplier should know more about the product and be able to catch any issue early avoiding design re-spin. So make sure this level of engagement is available (free schematic review etc.)
If all the above sections are positively addressed then you will have an enhanced experience and ultimately a successful product using a system-on-module.
>> Nigel Goodyear, Embedded Platform Architect