What is a System-on-Module (SoM)?

A System-on-Module (SoM) is a compact, pre-assembled circuit board that integrates the core components of a computing system—processor (CPU/MPU), memory (RAM), non-volatile storage (eMMC, NAND), power management, and often wireless connectivity—into a single, ready-to-use package. Unlike a full single-board computer (SBC) such as a Raspberry Pi, an SoM typically lacks built-in I/O connectors (USB, HDMI, Ethernet) and instead exposes its signals through edge connectors or high-density board-to-board interfaces. This design allows engineers to mount the module onto a custom carrier board that provides the specific peripherals, power regulation, and form factor required for their application.

SoMs sit between the extremes of using a fully finished SBC and designing a completely custom PCB from scratch. They offer a proven, tested compute core while leaving the application-specific hardware design to the developer. This approach is particularly valuable in embedded systems where reliability, time-to-market, and scalability are critical. Popular SoM ecosystems include those based on NXP i.MX, Texas Instruments Sitara, Rockchip, and AMD/Xilinx Zynq processors, with vendors like Toradex, Variscite, Digi, and PHYTEC providing robust hardware and software support.

Key Benefits of Using SoMs in Embedded Projects

Accelerated Development Time

Perhaps the most compelling advantage of an SoM is the dramatic reduction in development time. A complex processor design—including high-speed DDR routing, intricate power sequencing, and EMI compliance—can consume months of engineering effort. With an SoM, that work is already done and validated. Teams can begin application software development immediately on evaluation kits while the carrier board is being designed. The carrier board itself is simpler because it only needs to route lower-speed interfaces (GPIO, USB, Ethernet PHY, sensors) and provide power. Many vendors offer reference designs and software stacks that further shorten the cycle. For example, Toradex’s Verdin family provides a standardized pinout across multiple SoC options, allowing hardware and software reuse across product generations.

Lower Total Cost of Ownership

While the unit cost of an SoM is higher than the BOM cost of individual components, the total cost of ownership (TCO) is often lower. Designing a custom processor board requires significant NRE (non-recurring engineering) for layout, prototyping, testing, and certification (FCC/CE, etc.). SoMs come pre-certified for radio modules and EMC, saving thousands of dollars and weeks of testing. Additionally, procurement is simplified—you buy a single module instead of managing dozens of passives, connectors, and ICs from multiple suppliers. Over moderate to high volumes, the savings in engineering time, rework, and certification often offset the module premium. To see how different approaches compare, check the White Paper on System-on-Module Economics by Toradex for a detailed cost analysis.

Enhanced Reliability and Risk Mitigation

Commercial SoMs are manufactured under controlled conditions and undergo rigorous testing, including burn-in, temperature cycling, and vibration testing. This level of qualification is difficult and expensive to replicate in-house for low-to-medium volume projects. By leveraging an SoM, teams reduce the risk of hardware bugs (e.g., signal integrity issues on DDR, incorrect power-up sequencing) that can delay a product launch. Furthermore, if the SoM vendor discovers a hardware erratum, they will typically issue a revised module, and the carrier board design remains untouched. This decoupling lowers the risk of a flawed processor board derailing the entire product.

Scalability and Future-Proofing

SoMs enable straightforward scalability. A single carrier board design can support multiple SoM variants—for example, a low-cost Cortex-A7 module for basic IoT applications and a high-performance Cortex-A72 module for advanced edge computing. Because the pinout and physical footprint are standardized across the family, upgrading or downgrading the compute module requires no carrier board changes. This flexibility allows product lines to address different market tiers with minimal incremental engineering. It also future-proofs products: when a newer SoC becomes available, the module can be swapped to extend product life without a complete redesign. Variscite’s SoM portfolio exemplifies this with pin-compatible modules based on i.MX 8, i.MX 9, and other families.

Compact Form Factor and Simplified Carrier Design

SoMs pack high-density components (like multiprocessor SoCs, LPDDR4, and eMMC) into a small footprint—often as small as a credit card or even smaller. This allows the final product to be extremely compact, which is essential for wearable devices, portable medical instruments, and space-constrained IoT sensors. The carrier board, freed from handling high-speed routing, can be made smaller and simpler, often using only 2-layer or 4-layer PCBs. This results in lower PCB fabrication costs and easier assembly.

Applications of SoMs in Embedded Systems

Industrial Automation and Control

Industrial environments demand long-term reliability, wide operating temperature ranges, and deterministic real-time performance. SoMs based on Arm Cortex-A or RISC-V processors are common in PLCs, robotic controllers, and human-machine interfaces (HMIs). The ability to quickly swap modules enables maintenance and field upgrades. For instance, a factory control system using an SoM from PHYTEC can operate for 10+ years without a major redesign, thanks to the vendor’s long-term supply guarantees.

Medical Devices and Healthcare

Medical devices require stringent regulatory compliance and often run for many years. SoMs help meet these requirements by providing pre-qualified processing platforms. Applications include patient monitors, diagnostic imaging systems, and portable infusion pumps. Because the SoM handles the complex processor section, medical device companies can focus on sensor integration, user interfaces, and getting FDA clearance.

Internet of Things (IoT) and Smart Sensors

IoT gateways and smart sensors benefit from the low power consumption and small size of modern SoMs. Modules with integrated Wi-Fi, Bluetooth, and optional cellular connectivity—like those from Digi or Silicon Labs—allow rapid development of connected devices. The pre-certified wireless radios reduce the need for expensive FCC/CE testing of the entire product. Smart building sensors, agricultural monitors, and fleet tracking devices all leverage SoMs to balance performance with power efficiency.

Automotive Infotainment and Telematics

In automotive applications, ruggedness and reliability are nonnegotiable. SoMs designed for automotive grade (typically AEC-Q100 qualified components) can handle wide voltage fluctuations, thermal stress, and vibration. They power infotainment systems, digital instrument clusters, and telematics control units. The modularity also allows automakers to offer different feature sets across vehicle trims by simply changing the SoM.

Consumer Electronics and Smart Home Devices

Smart speakers, home security hubs, and appliance control panels often use SoMs to reduce time-to-market. The ability to quickly prototype with a reference design and then manufacture at scale is a major advantage. Media processor SoMs (like those based on Rockchip RK3588) can support high-resolution displays and AI inference, enabling voice assistants and gesture control.

Design Considerations When Using an SoM

Carrier Board Design

While carrier boards are simpler than a full processor board, they still require careful attention to power delivery, signal integrity for high-speed interfaces (USB 3.0, PCIe, GbE), and thermal management. Many SoM vendors provide carrier board design guidelines, layout reviews, and even reference schematics. Following these guidelines is critical to avoid issues like voltage drop across connectors or noise coupling. It's also wise to design for modularity: including a standard SoM connector (such as the Hirose DF40 or Samtec connectors) ensures you can later upgrade modules without redesigning the entire board.

Software and BSP Support

The SoM vendor typically provides a Board Support Package (BSP) including a Linux kernel, bootloader (U-Boot), device tree files, and drivers for the carrier board. Verify that the vendor offers long-term support, security patches, and an easy way to customize the BSP. Some vendors also support Yocto, Buildroot, or Android. An active community or professional engineering support is valuable, especially if you plan to deploy certified devices. For example, Digi's SoM ecosystem includes Digi Embedded Yocto with remote management capabilities.

Volume and Supply Chain

SoMs can be cost-effective in volumes from a few hundred to several tens of thousands per year. At very high volumes (100k+ annually), a custom processor board may become cheaper. However, supply chain risks must be considered. Relying on a single SoM vendor can be a vulnerability; choose vendors with multiple sourcing options or a road map for alternative modules. Longevity agreements and life-cycle management are important for industrial and medical products that need 10+ year availability.

Potential Challenges and Tradeoffs

While SoMs offer many advantages, they are not the best choice for every project. The unit cost premium over discrete components is real, especially for high-volume products where every dollar matters. The fixed physical footprint of the module can limit options for optimizing board shape or thickness. Also, the dependency on a single vendor for the compute core may lead to supply constraints or discontinuation. Finally, the integration of high-speed interfaces on the carrier board still requires skilled PCB layout, so the complexity is only reduced, not eliminated.

The SoM market is evolving rapidly. Key trends include the rise of heterogeneous computing (combining CPU, GPU, NPU on one module) for AI at the edge, the adoption of RISC-V cores in SoMs for open-source flexibility, and improved interconnect standards like PCIe Gen4 and USB4 that enable faster data transfer between module and carrier. Additionally, many vendors now offer “system-in-package” (SiP) modules that integrate even more components (like PMICs and RF front-ends) into a single package, further shrinking size. As embedded edge computing continues to expand, SoMs will remain a cornerstone of efficient product development.

Conclusion

System-on-Modules provide a practical and powerful approach for embedded system development. By delivering a pre-validated, compact, and scalable compute core, SoMs reduce development time, lower total cost of ownership, and improve reliability. They empower teams to focus on differentiating hardware and software rather than reinventing processor board complexity. While not ideal for every use case—especially extreme high-volume or ultra-low-cost products—the benefits often outweigh the costs for medium-volume commercial and industrial applications. As the Internet of Things, edge AI, and smart devices continue to demand faster innovation cycles, adopting SoM technology is a strategic decision that pays dividends in time, cost, and quality.