Arduino enthusiast Evan Kale has been the inspiration for a new Arduino powered Bluetooth adapter which has been created by DastardlyLabs to allow those interested to make their USB keyboards completely wireless.
The HID Relay takes the form of a small adapter that has been built using an Arduino Pro Mini, a Bluetooth module, a USB host shield together with a few other components.
Check out the video below to learn more about the HID Relay and the “Bluetooth-ification” process, thanks to DastardlyLabs who has created three videos.
The Arduino, Bluetooth module (check your specs, some HC-05, and HC-06 may come on a breakout board expecting 5V), and USB Host shield all run off of 3.3V, but devices you want to plug into the USB connecter will be expecting 5V. To deal with this you’ll want to supply the Arduino 5V via the RAW pin (it’s regulator will then supply 3.3V to VCC feeding the Host Shield and Bluetooth module). Then route a wire from this 5V source to the Host Shield’s power bus. A Bus power trace must also be cut on the Host Shield to prevent this 5V from damaging the 3.3V components there.
The Arduino/Shield can be soldered together with either on top, but I prefer the Arduino up to maintain access to the reset button and pin assignment silkscreen. It’s also a bit more compact as the Pro Mini will sit within the height of the Host Shield’s usb connector.
I recommend against permanently soldering the bluetooth module into this project, or at least connecting it’s power via a jumper or wire disconnect of some kind. Your programmer will be flashing the arduino on the same Rx/Tx pins your bluetooth module is listening on. Uploading a sketch is bound to fail if you can’t cut the bluetooth power.
My solution here was to mount the ProMini/HostShield sandwich onto some perf board with female headers on either side. The bluetooth module got glued to a perfboard “shield” with male headers which was easy to plug in and out of the base.