At a time when data are fast becoming the most important asset in many organisations there is a growing need for displays. With vast amounts of data helping to determine operational and business decisions, it’s vital that users are able to easily access data and visually monitor sensor readings generated across all types of applications.
So when it comes to developing a display based system, what are the critical elements that should be taken into account?
One of the most important is CPU choice. It is the brain of the entire module, driving all the I/O peripherals, display and touchscreen, or at the very least, is responsible for creating the data that is presented.
In an IoT system, its role is to join the I to the T, connecting ‘Things’ to the Internet and providing content for the local display.
Processors tend to be supplied as a complete Single Board Computer (SBC) or as a stripped down core module (COM).
The choice of processor, and the format in which it is delivered, are going to be key decisions. So, what factors do you need to consider when choosing between SBC and COM options and what are the key specifications to look out for? Finally, what design support will you need?
COM v SBC
Choosing between an SBC and a COM will usually mean a trade-off between time to market and flexibility.
A SBC is a ready to go instant platform that ships with all the drivers needed in the form of a board support package (BSP). It will have fixed computing, memory, and I/O sections integrated onto a single PCB.
A COM or system on module (SOM) is half-way between an SBC and a discrete microprocessor IC. It offers more flexibility than an SBC, but without the development effort associated with a discrete solution. The COM will contain the processor and memory and is then mounted on a separate carrier PCB containing the I/O section of the design.
Clearly, using a SBC saves a lot of integration effort and development time. It comes out of the box as a fully working solution that just needs to be loaded with the application software and interfaced to the display. Problems usually arise when it comes to size and I/O. Each manufacturer offers a limited range of SBC options with different and fixed permutations of I/Os, size and features.
So it is a matter of selecting the most suitable option from the range – you can’t customise the board in accordance with the needs of the application. If a key interface is lacking, then it is sometimes possible to create an adaptor, using the pin header frequently provided. If the board won’t fit into the system caseworks, well, that’s generally a deal breaker.
The advantage of the COM is that you can design the carrier board exactly according to your size and configuration requirements, and then connect an SoM to it. This will take time and design effort, but will allow you to create a board with exactly the I/O that you need for your design and of the right form-factor.
In addition, if the need arises for example to add new I/O options, you can simply redesign the carrier board and continue to use the same COM. It may also be possible to upgrade the processor and the memory later without rebuilding the base board, by using a pin-compatible replacement module.
There is also a third potential way in which some suppliers have developed their own ranges of baseboards with interchangeable core modules. You can start your development on these platforms, work on the software and in the meantime, develop your own baseboard if you choose to.
Key considerations
In choosing a SBC or COM, the decision will depend on the specific project requirements and sales volume. Whichever route you opt for, the most important specifications will include:
• The interfaces provided for sensors and actuators; how many are there, and are they the right ones;
• The connectivity options for the network and Internet;
• Support – which can make a big difference to how long it takes to get your project up and running;
Other things that matter include: temperature range; the longevity of supply and power – especially if it needs to run from a solar panel or battery and last, but by no means least, is the cost. If a board is to be sent out into the field in any volume, budget is always going to be a factor.
| Above: An SBC is a ready to go instant platform that ships with all the drivers needed in the form of a BSP |
Choosing a supplier
Having drawn up a shortlist of boards that tick the technical boxes, it is well worth taking a hard look at the organisation you’re sourcing the board from.
What constitutes a good supplier? They can make a huge difference to your time to market. So always consider the following:
What is the pedigree of the manufacturer of the board? Do they have a reputation for producing quality, stable products? What long term availability guarantees do they offer?
Is there a board support package for your chosen operating system? Does it contain all the drivers that you need? Have they been properly tested to work together?
What is the technical support like? Where is it located?
Is there a local representative able to support you? How knowledgeable are they?
How well does technical support know the specific board that you’ll be working with and are they familiar with other key system components like the display? Have they performed the similar integrations in the past?
How good is the documentation? A great question this one – a well-documented design is often a sign of quality.
Does the vendor or the local representative offer value added services?
What is the tool support like? Are there debugging tools available and what is the cost?
That list highlights the need to work with a quality industrial vendor. While you can have fun with a well-known hobbyist platform, if you apply the above tests, then it becomes clear that they are not a sound basis for professional embedded systems development.
A community isn’t a substitute for expert professional technical support, and is your organisation happy to expose aspects of their product development online when you post questions to the community?
In conclusion
When it comes to selecting a processor, the choice will usually boil down to balancing just three key factors: processor performance and specifications; format: SBC or COM (not all processors are available in both of course); and finally, the supplier and the support they can offer.
Selecting the optimal processor but working with a supplier who isn’t willing or able to help you with the design issues you’ll encounter on your journey can significantly lengthen your time to market and even put the success of the project in jeopardy.
So take some time to assess, so you get it right first time round.
| Author details Rhett Evans is Embedded Systems Sales Manager, andersDX |
