Key Factors To Choose The SOM
System on Modules (SOMs) have become an integral part of modern embedded systems, offering a compact and efficient way to deploy computing power in a variety of applications. From IoT devices and VPNs to firewalls and cellular gateways, selecting the right SOM can make or break your project. While there is ample information available about x86 CPUs, RISC-V, and AI-focused SOMs, this article zeroes in on ARM-based SOMs and their use in networking and IoT applications. Here’s a comprehensive guide to help you make an informed decision.
Key Factors
When selecting a SoM or SBC, several critical aspects should be considered
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Chip Provider
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CPU Computing Power
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Supported RAM Size
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Wireless Connectivity
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Ethernet Speed
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Available Interfaces
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Power Consumption
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Ecosystem Maturity
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Price
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Network Accelerator
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Crypto Engine
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Operating System
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SoM Providers
Chip Provider
The choice of chip provider is a foundational decision. Popular options include Qualcomm, MediaTek, Broadcom, Realtek, Rockchip, and NXP. However, some providers have unique constraints. For example, Broadcom's chips are primarily exclusive to Raspberry Pi devices customized chips. Each provider has its strengths, so aligning their offerings with your requirements is crucial.
CPU Computing Power
ARM-based CPUs range in computing power from Cortex-A7 to Cortex-A76 cores. The choice depends on your application’s performance requirements. For basic IoT devices, a Cortex-A7 might suffice, whereas more demanding tasks like cellular gateways may require the higher performance of Cortex-A73 or A76 cores. The table below shows the comparison of the CPUs:
Supported RAM Size
RAM size is a critical yet often overlooked factor. Most ARM-based SOMs support RAM sizes between 1GB and 8GB. Interestingly, Qualcomm’s older CPUs support only up to 3GB of RAM due to hardware limitations, though newer models address this issue. Ensure your selected SOM can accommodate the memory demands of your application.
Wireless Connectivity
For applications requiring wireless connectivity, WiFi capabilities are a key consideration. WiFi functionality falls into two categories: Access Point (AP) or client mode. Qualcomm and MediaTek excel in AP functionality for multiple client connections. Realtek’s AP performance and stability could be a concern, and Broadcom’s chips may be difficult to source in the market
Ethernet Speed
For IoT applications, 1GbE Ethernet is typically sufficient. However, for high-speed applications like WiFi or cellular gateways, more than 1GbE may be necessary. Qualcomm, MediaTek, and Broadcom offer built-in support for 2.5GbE PHY or SGMII+ interfaces to meet these demands and NXP chips offer 1GbE only interface for the i.MX series.
Operating System
Selecting the right operating system (OS) is crucial before choosing the SoM. Popular OS options include Linux, Debian, Ubuntu, and Yocto. For WiFi-based applications, OpenWRT is widely recognized as the go-to open-source solution. MediaTek provides extensive support for OpenWRT, particularly since their strategic shift in 2022-2023. Qualcomm offers AthxK, but its OpenWRT release is less up-to-date, not fully open-source, and may require some technical expertise for integration. If you opt for Qualcomm, it's recommended to stick with their QSDK for more robust support.
For VPN or firewall applications, Debian/Ubuntu is typically the better choice. However, at least myself haven’t found Ubuntu is able to run on any Qualcomm chip yet. Other vendors, such as MediaTek, NXP, and Rockchip, offer better support for these environments.
Network Accelerator
Without a network accelerator, all data packets have to pass through the CPU, which can lead to performance bottlenecks. Both Qualcomm and MediaTek SoCs accelerate packet processing, especially for WiFi-to-Ethernet or Ethernet-to-WiFi communication. It's essential to verify whether other interfaces, such as LAN-to-LAN or USB-to-LAN, are also supported
Crypto Engine
For applications requiring encryption, the presence of a crypto engine is vital. For instance, MediaTek’s MT7988A Quad A73 CPU supports the EIP197 crypto engine, though some limitations exist regarding the number of cores that can handle encryption tasks simultaneously.
Available Interfaces
Industrial applications often require versatile interfaces like UARTs, GPIOs, SPI, and I2C to support peripherals such as CAN buses, RS232/485 connections, or DIDO modules. Ensure the SOM provides sufficient interfaces for your specific needs.
Power Consumption
WiFi integrated SoC normally consumes higher power and thus makes the thermal tougher to resolve. Hence if the applications is WiFi centric, special care should be paid on the thermal solution in order to achieve the performance expected.
Temperature Range
For industrial environments, the operating temperature range is critical. NXP stands out with its full range of industrial-grade chips supporting temperatures from -40°C to 85°C or even 105°C. Qualcomm offers selected industrial-grade options, while MediaTek lacks chips designed for extreme temperatures.
Price
Price should be considered after confirming that the SOM meets all technical requirements:
- Rockchip: Offers excellent cost-to-performance ratios but may raise geopolitical concerns.
- MediaTek: Aggressively priced but lacks industrial-grade options and has questions around hardware acceleration.
- NXP: Higher cost but delivers industrial-grade reliability, a mature ecosystem, and extensive OS support.
Final Thoughts
Choosing the right SOM involves balancing performance, features, ecosystem support, and cost considerations against your application’s specific needs. Whether you’re building an IoT device, a VPN solution, or a cellular gateway, understanding the nuances of each factor—from chip provider to operating system compatibility—can help you make an informed decision.
Carefully evaluating these factors will ensure that you select the most suitable SoM for your network, IoT, VPN, firewall, or cellular gateway application
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