One Button for IO and Power Control

For an e-kayak project that he’s been working on, Braden Sunwold needed a way to have his device wake from sleep and take input from a single button. While this might seem impossible at first glance, consider that the same sort of thing is done with consumer products, such as the iPhone’s power button. Sunwold created a PCB that's smaller than a quarter to facilitate this dual-use button setup, using an STM6601CA2BDM6F smart push button controller IC that itself is smaller than a grain of rice.

The board is designed to accommodate a small onboard button for power/IO purposes, and can also be wired to an external trigger. This external capability came in quite handy during testing, as the onboard button was laid out incorrectly, though one might expect this error to be corrected at some point in the future. The device also features a LiPo charging circuit via an MCP73831 chip, along with USB and battery connections, making it an all-in-one power/input solution for electronics projects.

The build is outlined in the video below, including several mistakes that Sunwold made along the way. Notably, if you’re going to solder your PCB with a clothes iron, be sure to have a plan to extract the PCB after the process is complete. Details on this advanced button PCB build are found here and here. PCB files are on GitHub if you want to examine the design in detail – or perhaps even build your own.