Manufacturers of embedded systems have long known about the benefits and trade-offs of basing designs either on discrete microprocessor components or on a ready-made system-on-module (SOM). This is often referred to as the Make or Buy? dilemma.
These arguments are well understood by OEMs – but a new factor affecting the choice is perhaps less so – the benefits of designing for resilience. The problems currently plaguing the car industry show how much economic damage can follow from severe disruption in the semiconductor supply chain. When a design is reliant on a single source of a key component that is not easily substituted, the production line is then at the mercy of that component’s supply channel – that component is the product’s weakest link in the chain.
The causes of volatility in the semiconductor supply chain
Component shortages or extended lead times can also hamper a factory’s ability to maintain normal production operation. If this happens, it is not easy for the OEM to quickly implement a Plan B. Microprocessor substitution is difficult, taking considerable development effort and time. Supply chain disruption to the either microprocessors or companion chips may cause an embedded system OEM’s production line to be halted, resulting in substantial financial impact. This has important bearing on Make or Buy? decisions, because the use of a SOM helps to insulate OEMs from supply chain issues.
- The small pitch of BGA packages calls for specialist layout expertise to design the fan-out from the microprocessor. Special production machinery and a high-cost multilayered PCBs are also mandated.
- High-speed bus interfaces and high-speed DRAMs both require expert design capabilities. Dedicated CAD tools are used to configure the track timing, impedance, isolation characteristics, and shape of the PCB routing to be compatible with the tolerances specified by IC manufacturers.
If the OEM decides to make rather than buy, then, it is exposed to the risk of a single source of supply, alongside the requirement to manage dedicated engineering teams, and undertake a long and complex development process. Even when a development is completed, the OEM must install advanced production equipment and processes to manufacture a high-cost PCB.
Figure 2: An iWave ITX SBC iW-RainboW-G50S SOM
SOM: Offloading the risks
In return for the premium paid via the SOM’s higher unit cost, the OEM gains several valuable benefits:
- Product designers can concentrate on unique features which provide added value.
- SOMs are supplied in standard form factors – so if the SOM supply from one manufacturer fails, it can be replaced by one from a different manufacturer featuring the same microprocessor.
- The standard footprint also enables OEMs to migrate a design from one generation of a microprocessor family to the next without redesigning end-product hardware. This capability also supports development of end-product designs with low-end, mid-range and high-end versions.
- Use of a SOM dramatically shortens development time, resulting in faster time-to-market.
The new Open Standard Modules (OSM) form factor was developed under the aegis of the Standardisation Group for Embedded Technologies (SGeT). It provides numerous benefits, including:
- Increase I/O density.
- Meeting demand for smaller, lower-cost embedded computer modules.
- Offering pin-compatible options for swapping between different IC manufacturers and different Arm processor architectures.
- Support the development of product families with different I/O options via the provision of four pin-compatible form factors – thereby eliminating the need to redesign a product’s carrier board for each new end-product variant.
Already, these form factor options are well supported by commercial suppliers of OSM modules. For instance, iWave supplies OSM modules featuring microprocessors from NXP, Renesas and STMicroelectronics.
Table 1: OSM modules available from SOM manufacturer iWave
When Future Electronics supplies an iWave OSM module to an embedded system OEM, it can also provide a rich choice of supporting technologies – including a single-board computer for application porting and testing, and associated components (like camera modules, TFT displays, enclosures, heat sinks, wireless modules, GNSS positioning sensors, etc.