Modules, Dev Kits, and Custom PCBs: Which Should You Use?

Created: August 23, 2022
Updated: July 1, 2024

Back in the good old days of 2018, when everyone was dealing with capacitor shortages instead of semiconductor shortages, development kits played a role in marketing and proof of concept rather than system design. It’s common to buy development kits for a few critical components when they are available and use these to build and test an embedded application. They are also great for experimenting with the functionality you need, as well as learning how to use a new component.

Now with all the supply chain woes and the inventory glut of development boards, I have been seeing more projects where designers are leveraging a development kit or a module like an SoM. They will start with the development kit or SoM, and build a baseboard/expansion board around it that provides the additional functionality. Some of these projects are prototyping efforts that give a low-risk path to a proof of concept, while others are full-fledged products that will be produced at high volume.

So which path is best for your new product? We’ll break down the pros and cons.

Why Build Around a Module or Dev Kit?

Modules and development kits complete boards that can be instantly deployed in a new system or as a standalone part in an electronic assembly. Semiconductor vendors offer these boards and kits for designers to use as application development tools, for proofs of concept, and ready-made products that can run an entire system. Historically, these were marketing tools and have always been a loss leader for semiconductor vendors because they were produced at low volume. The idea was to give designers a product that helps them prove out a new application before they make a large purchase of parts.

A related approach is to use pre-made board modules or systems-on-module (SoMs). These boards are developed by 3rd parties, so you may not receive the same level of development support as you would with the purchase of a development kit. However, this approach is arguably more popular than adapting a dev kit due to the community support available for many popular products. Some of the most popular options being used in production are Arduino boards and Raspberry Pi, although other very popular boards like ESP32 and ESP8266 NodeMCU are making their way into production-grade products.

Module selection is normally driven by the main component on the board (usually an MCU or FPGA), as well as how this will be used with any other peripherals in the end product. When working with these modules, there are generally two possible approaches: either use the module on its own with no additional peripherals or build a custom base board that provides connections to some peripherals. The latter is a popular route as it gives you the flexibility to build something custom around a proven platform while reducing overall cost.

Advantages and Disadvantages of Modules

Proven products - With the exception of some 3rd party products or open-source designs, these products have been proven by designers and popular modules will usually have plenty of design resources available.
Access to peripherals - Development kits and modules generally provide access to every peripheral and pin on the main processor. The idea is to allow a designer to experiment with different connections or external modules.
EMC compliance - Since these products are produced at high volume and are freely available for purchase, they are required to have passed EMC compliance testing.
Access to design files - Some development products will have design files available that can be adapted into a new design directly from the development product. The same idea applies to open-source designs.

Overall, these factors reduce the risk for designers and application developers. Conversely, there are some reasons to bite the bullet and develop a totally custom board:

No control over form factor - When you purchase a module, what you see is what you get. You’re stuck with the form factor of the board and you will have to build everything around it.
Difficulty adapting into an assembly - This is an offshoot from the previous point; it may be difficult to build a complete assembly that meets the user experience requirements or ideal form factor of an end product.
Unused I/Os or peripherals - Modules will provide access to every peripheral on the main host controller for purposes of experimentation. This can actually be bad and it drives the size/cost of the development board.
Supply chain - If you’re planning to produce at a high volume over a sustained period, it might be difficult to find some development kits directly from the vendor. Arduinos and Raspberry Pis are usually in huge supply, but dev kits may not be available in the same quantities.

One aspect that is difficult to address is cost. If you compare the development board cost (normally under $100 per board except for large FPGA products) to a custom board cost, you’ll find that custom boards need to be produced at a very high volume to be cost-competitive with an off-the-shelf module. Consider these development points, your risk tolerance, and your budget carefully before opting for a module or development kit.

How to Find Development Kits, Modules, and Parts

Not all parts will have development kits, but the selection of development kits is normally driven by the capabilities of specific parts. If you can’t find a development kit, but you want a faster path to a complete design, one option is to use a component with a reference design available. Sometimes, the publicly available reference design material matches the development kit, so most of the engineering required for your product will already be completed.

Starting with an open-source design that has been thoroughly developed is also one method for accelerating development. Some modules (most notably Arduinos and cloned variants) are available as open-source designs that can be copied and modified, or they can be used with a custom baseboard. If you go either route, consider how the module will mount to the baseboard. Options include SMD soldering for castellated modules, pin-headers (usually found on MCU boards), and mezzanine or other board-to-board connectors that provide power and high-speed data.

Because development boards might have an inconvenient form factor, exposed I/Os that aren’t needed, or they lack compatible connections to peripherals, custom boards are still the most popular option for building new products. For more popular modules like Arduino, some companies will sell application-specific baseboards, which puts the burden on the customer to procure their required volume of modules. In both cases, you’ll need to find some of these parts for custom baseboards or processor boards:

There are many other components that might be needed in these custom systems that can’t be found on a single-board module or dev kit. To help you find the parts you need, use the advanced search and filtration features in Octopart. When you use Octopart’s electronics search engine, you’ll have access to up-to-date distributor pricing data, parts inventory, and parts specifications, and it’s all freely accessible in a user-friendly interface. Take a look at our integrated circuits page to find the components you need.

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