Design Reviews for Open-Source PCB Projects

Who doesn’t love a great open-source PCB project? They are a great way to get good ideas for new designs, some advice on how to build certain circuits. For the hobbyist, open-source designs can be like an idea factory. For the pro designer, open-source designs are often avoided. If you do plan to base a new product around an open-source hardware project, what’s the best approach to take? Before you go jumping head-first into an open-source PCB project, take a look at the points below to make sure you’ll be successful.

What to Inspect in Open-Source PCB Projects

Before you start building a custom project around an open-source PCB project, you should perform a thorough review of the design. Make sure to inspect the areas outlined below as any of these problems can delay or derail the product, in which case it will be best to start a project from scratch.

The Schematics Might Be Totally Wrong

Just because a design has been open-sourced doesn’t mean the design is totally correct. It’s possible that the circuits were designed wrong, or there might be other mistakes in the schematic. If these problems were present in the original schematics, they will then be translated over to the PCB layout. The result is a PCB layout full of problems and a non-functioning design.

To spot these problems, you have to know something about the portion of the design you want to use, and you should make sure you read up on the main chipset in design so that you know how to use it. This is all part of a standard design review you would perform with an original design, so don’t assume that anyone else has reviewed the open-source project before you’ve looked at it thoroughly.

Is this PIC32MX schematic incorrect? Make sure to look at the design thoroughly to spot any errors.

If you are skeptical of the accuracy of an open-source project, there are a few things you can do to investigate.

• Do a Google search for the project name and see if anyone else is talking about it. If there are problems or complications with the design, someone might have posted about it on a forum like Stackexchange.
• Compare with the main component’s reference design (if available). If there is a reference design available, this is going to be your best bet for assessing the accuracy of schematics.
• Compare circuits with application circuits in datasheets. You can usually spot some of the most obvious errors by comparing the design with any application circuits found in component datasheets.

Perform a Thorough DFM Review

An open-source project that was recently updated and has the newest components might be sourceable, even at high volume. However, if the PCB layout was not created properly, then you might find that the design cannot be manufactured without defects. Make sure to give the PCB layout in an open-source hardware project a thorough DFM review before copying portions of the layout into a new design. This should be the same design review you give to a totally custom PCB. The easiest way to get started is to apply DFM-ready design rules and leverage the DRC engine to identify problems in the PCB layout.

Community Involvement

If you found your open-source PCB project on a platform like GitHub, check to see how much involvement it has seen from other designers. GitHub has features that allows other users to flag problems in a project, propose solutions, and push these into the newest release of the project.

Unfortunately, due to the big deficiency in the number of hardware designers that operate on open-source platforms, it might be difficult to find a lot of community support for the hardware side of an open-source project. The firmware/software side is another story; developers tend to be much more active on popular coding projects. When there is more involvement from the developer community, it’s more likely that the outstanding bugs have been identified and corrected.

Check the Issues tab if you’re looking at open-source PCB projects on GitHub. From there you’ll find any problems that have been identified by other designers and developers.

What About Reference Designs and Evaluation Products?

A lot of what was stated above also applies to reference designs and evaluation products. There is one difference that is pretty critical: reference designs, evaluation products, and even some 3rd party designs will receive some scrutiny from a semiconductor vendor. For example, in reference designs and evaluation products that are based around specific processors like an FPGA, they were designed, tested, and qualified by the semiconductor vendor.

For these reasons, you can usually put a lot more faith in reference designs. The schematics are meant to show exactly how you should use the main component or chipset that is highlighted in the reference design. For the PCB layout, it’s debatable to what level you should try to replicate the reference design. Think carefully and evaluate the PCB layout closely before you simply copy it into your own design.

If you want to reuse open-source projects or adapt them into your own designs, make sure you use OrCAD, the industry’s best PCB design and analysis software from Cadence. OrCAD users can access a complete set of schematic capture features, mixed-signal simulations in PSpice, and powerful CAD features, and much more.

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