I suggest soldering the wires to the Trinket from the top (as shown on the picture below) so that there is no clearance issue at the bottom. The connections are shown on the fritzing diagram at the bottom of this page. There are just 7 solder joints to make on this project. Tip: I recommend using solid core wires for this project as they are easier to solder and work with and they will not be exposed to repeated flexing. The enclosure will need to have a hole cut to insert the USB plug. The Trinket must be very solidly mounted to the enclosure to sustain the high stress of USB cable insertion. Do not buy buttons that need to be soldered to a board. Buttons should attach to the enclosure.

Here are some parameters worth considering when picking an enclosure and buttons: I added the references in the hardware list, but these are by no means the only or best options.

I just went to my local electronic store and bought some I liked. There is a wide choice of enclosures and buttons to do this project. The SAMD21 inside the new Trinket M0 has USB keyboard and mouse capability in hardware and it has shown to be perfectly reliable. The original Trinket is ATtiny85-based and that chip does not have native USB keyboard capable hardware, so the project uses a bit-banged (i.e. This worked, but not completely reliably, especially behind some USB hubs. I had originally made this project with the older Adafruit Trinket 5V using the Adafruit Trinket USB Keyboard instructions. I like the Trinket M0 because it is really small (and this project only needs a small number of I/Os, so no need for the bigger boards) and it is inexpensive ($8.95). It can be replaced by pretty much any of the other Atmel ATSAMD21-based boards like the Arduino MKR ZERO or the SparkFun SAMD21 Mini Breakout. The key component for this project is the Adafruit Trinket M0. It saves me from having to reach for the keyboard or remembering keyboard shortcuts. This is a very simple, yet useful introductory project to Arduino, USB and buttons.

Adafruit trinket 5v first project