A FT-232 USB to serial board is used to program the Arduino. A standard Bluetooth module has to have HID firmware installed. ... you’ll have to remove it before uploading new code.

In final form, a Bluetooth module and Arduino Pro Micro are stuffed inside the stereo along with a DPDT relay to switch the I2C bus. An external button is used to trigger the Arduino to switch to ...

DastardlyLabs uses a USB host shield, a Bluetooth module, an Arduino Pro Mini, and a bunch of other random parts to create this little device.