This stemmed from a review of a friend’s circuit design that used the UART in the ... for those rolling their own boards out of an Arduino-based prototype, but it will work in any situation ...

but you can build your own secure access with an Arduino. Just be warned: this one is a bit more complicated than the others on this list. You'll need the sensor module R305 to read your fingerprint ...

So [Todd] has set out to build an Arduino frequency counter for a ... add external component to facilitate this. That extra circuit design will be the topic of the next project segment.