A simple application for USBreadboardIT is the BIGHID button (that is, a BIG HID button). It emulates an USB HID keyboard (so, no drivers) annd sends a single keypress or key combination, that can be bound to an usOr-defined action.

It is based on two excellent pieces of software:

• The m-stack USB open source stack by Signal11, that emulates the USB HID keyboard (specific code here)
• The PIC16F1-USB-DFU-Bootloader by majbthrd, that allows for dfu firmware updates through dfu-util

The hardware part is very simple: a button is tied between a pulled-up input pin (RA3) of the board and GND. A USB cable is connected to corresponding signalls on the headers.

The first software step has been performed uploading the DFU bootloader through a pickit2.

Once the bootloader is working, connecting the usb cable to the PC while holding the button pushed exposes the bootloader to the OS and dfu-util can be used to upload code to the board.

Code has to be compiled in MPLABX with the following options:

--codeoffset=0x200
--rom=default,-0-1FF,-1F7F-1F7F  

Produced HEX file must be converted to proper dfu file through 454hex2dfu (included into bootloader repo):

454hex2dfu MPLAB.X.production.hex hidkbd.dfu

Then the obtained dfu file can be uploaded with

dfu-util -D hidkbd.dfu

The button has then to be connected and re-connected to start keyboard operation.

The firmware polls RA and sends CTRL+SHIFT+1 when the button is pressed. OS bindings are then used to catch this combination.