Do you need to build an embedded system quickly with minimal risk to your pocketbook? One of the fastest ways to get the embedded computing capabilities you need in a compact package is to use a single-board computer (SBC). These can be purchased off-the-shelf from major distributors and directly from SBC vendors. Some SBCs can also be found online as open-source projects, which allows you to download and build the board with a manufacturer.
While these are convenient pieces of hardware, should they be relied upon for every system? There are some important reasons to shy away from an off-the-shelf SBC as a computing platform for an embedded system. These reasons largely relate to hardware revision, cost at volume, and the availability of vendor or developer support for your product.
Why Off-the-Shelf SBCs?
SBCs are compact systems that include all of the required interfaces, external connections, drivers, adapters, and chips one would need to build a simple computer. Some of the most popular SBC brands include Raspberry Pi, BeagleBone, Toradex COMs, and Tinker.
One reason off-the-shelf SBCs are so popular is because they give designers a very quick way to build a new embedded system. Designing any computing system is a complex, time-consuming undertaking, but off-the-shelf SBCs cut out much of the design time and allow a focus on the product’s application or ecosystem.
- Pre-qualified hardware: SBCs are normally pre-qualified against basic compliance standards, specifically EMI/EMC compliance requirements.
- Not hardware experts: Developers who are not hardware experts can still create a new product by leveraging SBCs as they will not need to create a custom board.
- Focus on the application: Products that have an embedded application as the main value-add do not always need a custom board, they just need computing power.
- Focus on peripherals: Sometimes the main value-add is also in the peripherals; using an SBC as the main system controller allows for a focus on just a custom peripheral.
For the embedded developer that wants to deploy a new application to market, SBCs bring plenty of value. They also make for excellent prototyping platforms, which is why they are sometimes also used as 1st generation products. What are some of the downsides to relying on SBCs?
Downsides of Off-the-Shelf SBCs
When it comes time to scale a product into the marketplace, many times an SBC will need to be eliminated in favor of a custom PCB. There are three major reasons for this.
Single-board computers are typically intended for general-purpose use. This brings up the question of reliability in certain environments. For example, in industrial systems, harsh environments (aerospace or automotive), high temperature environments, or anywhere with a risk of ESD, there may be greater potential for device failure. Most off-the-shelf SBCs may not meet specific industry reliability standards (UL, DO, IEC, etc.) for high-reliability applications, so they would need to be qualified extensively before use. Given the time and costs of qualification, a custom PCB might be a better option.
Unless you are actively involved in open-source projects, or you are actively involved in development of the SBC platform, you will have no control over hardware revisions. You might not even have knowledge of problems with the platform until a new revision is released, or until the system fails to operate as expected. This could force deploying replacements in the field, and these service costs to customers can be excessive. When deploying products at scale, the lack of control over revisions motivates development of a custom PCB for your product.
Off-the-Shelf Hardware Costs
Many single-board computers have reasonably low per-unit cost, which can be very competitive compared to building a custom PCB from scratch at low volume. Once you move to scale, the per-unit cost of an off-the-shelf PCB becomes too large and it makes more sense to produce a custom PCB. The costs involved in electronics manufacturing can drop rapidly above a certain production volume due to reduced volume materials and components prices.
Off-the-Shelf or Custom?
Just from a cost perspective, it makes most sense to use an off-the-shelf platform for products being sold at low volume. For high-volume products, the lowest-cost path forward is to design a custom PCB and enclosure.
In some cases, the design data for an off-the-shelf SBC could be available as an open-source hardware project, which means a designer can use these as the basis for a custom design. Other ways to take advantage of an off-the-shelf design in a custom product include:
- Using a custom base-board to connect to an off-the-shelf SBC
- Reverse engineering an existing SBC
- Using compute modules (SOMs or COMs) to build a modular product
Before you finalize your entire product around an SBC, make sure you have a realistic plan to build a custom hardware platform that cannot be easily reverse engineered. SBCs can help you get through a prototyping and beta release phase without the expense of custom PCBs, but eventually you will have to make the leap to a more professional hardware platform.
Whenever you need to create a system-level design with an SBC, or you want to design a custom PCB for your system, use the powerful industry-standard PCB design features in OrCAD from Cadence. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity.