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Best RS232 Breakout

Key technologies: RS232, Upverter, dirtyPCBs

I’m frustrated with the lack of good RS232 breakout boards. All I need something that lights up, is clearly labeled, and provides good test points for my oscilloscopes.

At OSI, we do a lot of debugging of RS232 serial ports. Serial ports are surprisingly hard to debug. The signals are poorly named, different devices use the signals differently, and there are several communications settings that need to be configured. If you get anything wrong, it just doesn’t work; you don’t get any clues about what needs to be fixed. We work with a lot of legacy field equipment, and we often need to break into the signal and get some clues about how to get the systems communicating.

Our existing breakout boards are pathetic. One of them has LEDs but no test points, which prevents us from attaching our oscilloscopes and checking signal integrity. Another has test points that aren’t labeled and require jamming small bits of wire into holes. Another breakout board is for a 25-pin DB25, which requires a complicated string of DB9 to DB25 and male-male gender adapters. Even if I did want to use these boards, they’re almost always already in use. Debugging RS232 is a frustrating experience.

We searched online for some better breakout boards, but they turned out to be surprisingly expensive. The good ones are well over $50 each, and even those don’t have the perfect set of features.

I decided to spend a few hours building my own breakout board. It took less than 8 hours to design and order the boards.

I used for schematic capture and PCB layout. They have a great “parts concierge” service that will create symbols and footprints for you automatically. I put in a request for three symbols/footprints, went to a 1/2 hour meeting, and had the parts ready for me when I got back.

I ordered a 10-pack of PCBs from for only $25. I got the boards in a few weeks, and they looked great.

The components were more expensive; I paid about $30 for enough components for a single board. The cost would go down significantly if I ordered these parts in higher quantities.

The board works great; I can probe the signals easily. I have plenty of ground test loops to attach the grounding alligator clips. The lights are sometimes hard to read at higher baud rates with single-character messages, but that is expected. There is still enough of a flicker at 115200 to let you know that a character was sent.

My project design files (schematic, layout, BOM) are available on Upverter here.

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