USBreadboardIT

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.

I noticed today that published pinout where not correct: USB D- and D+ pins were swapped in the image.

Issue has been corrected.

Board is working! The classical blinky test past smoothly and now an initial version of the test - and maybe other usages - firmware is ready and uploaded on Github: Link

I assembled the first USBreadboardIT unit, completely by hand (have I mentioned that USBreadboardIT have been thought with hand-assembly in mind?). D1, that is the "power" LED tied to VDD, lights up when connected to power, so at least the power works, both at 5v and 3.3v :)

Regarding the microcontroller, I used a PIC16F1454 because it's bigger brother PIC16F1455 (with analog capabilities added) was out of stock when I tried to order it. They are pin-compatible, so USBreadboardIT will work anyway.

Wonderful purple PCBs arrived from OSHpark, time to assemble USBreadboardIT!

Yesterday I sent the PCB to OSH Park! It should arrive in one month (manufacturing plus shipping to Italy).

I uploaded on Github the design files (kicad source plus gerber), together with a - unfinished - test application (written in python plus Qt) to control the board through USB HID.

After some digging, I found an interesting USB bootloader fitting in only 512 words for PIC16F1455:

https://github.com/majbthrd/PIC16F1-USB-DFU-Bootloader

For this to work I have to add to the board a pushbutton on RA3 (the same pin as reset) and thus rrearrange the board a bit; after that I will send the board in production.

Stay tuned!