USB Foot controller resources?

[WyndBalduram]

I would like to build a foot pedal that utilizes 5 spst momentary switches to output keyboard keys through usb to a PC.  I would like to do this without hacking up an old keyboard, because I would like to design the circuit from scratch to get a slightly better understanding of interfacing analog hardware to usb devices.

Does anyone know of any IC's I could use, or resources which can point me in the right direction to accomplsh this? 

Thanks in advance.   

[g_u_e_s_t]

how deep down the rabbit hole do you want to go?  the easiest diy approach is to get a makey-makey.  it takes care of all the code for making keystrokes and such.  the next level would be to get an arduino leonardo or micro, as there are libraries for them.  if you want to make your own pcb, the FTDI usb->serial chips make life a lot easier, if you are already familiar with programming 8-bit micros.  most 32-bit micros have USB peripherals already.

[PRR]

> spst momentary switches to output keyboard keys through usb to a PC.
> ...to get a slightly better understanding of interfacing analog hardware to usb devices.

What analog hardware? It's all switches and code.

Emulating an IBM keyboard and then USB is indeed a rabbit-hole or two, and not generally useful (IMHO) for other projects.

In this case, I'd hack a keyboard and move on to the next interesting problem.

[WyndBalduram]

I guess I was under the impression that I would be able to purchase a chip that already had the ability to do what a keyboard does (translate key presses to digital signal), because there only seems to be a single IC on the circuit boards of the keyboards I have hacked open.  That way, I could just map the switches up to each of the necessary pins of the IC to make it spit out a keystroke.

I have considered hacking a dell keyboard for this purpose, but wanted to be able to build more than one of these usb stomp switch boxes without having to buy and gut a keyboard every time.

I've done a little bit of research regarding microprocessors, but at this point in time they seem a little over my head.  Since I am just beginning this foray, I figured a good starting point would be using switches to make something happen digitally.  I guess this is just basic stuff though, huh?  

edit: I just realized something - the single chip in the keyboards I have seen are microcontrollers that were pre-programmed to function in the keyboards, weren't they?  Sorry for my ignorance.   

[deadastronaut]

yep pre programmed...

i wanted to butcher a mini midi keyboard (korg nano 16 pad) to use as a drum kit..(make my own big pads)

but those 'pads' that the keys hit are not easily replicated AFAIK ...its easy to wire up straight to the key, but it will not be velocity sensitive...

that's as far as i got and gave up...drums with no velocity sounds crap... ...and may as well have used a usb qwerty instead.

[tommy.genes]

Livid Instruments have a line of DIY MIDI modules called Builder.

The Brain Jr looks especially interesting and relatively affordable.

I've not used any of these items, so I can't provide any further input based on experience.

-- T. G. --

[tommy.genes]

The links I just posted were light on info. Check out the Brain Jr Wiki page for a whole lot more info.

-- T. G. --

[deadastronaut]

^ excellent link..

[PRR]

> only seems to be a single IC on the circuit boards of the keyboards

Back in the dawn of time, the IBM PC keyboard had a 8048 microcomputer inside the keyboard.

Since then everybody has used the same idea. The output has changed from a crude serial format to USB. Apple maps the keys a bit different than IBM types.

Keyboard scanning and debouncing is not a trivial task. (Moreover the IBM keyboard also does rollover and buffering and some code conversion, though these may not matter to you.)

> able to purchase a chip that already had

Probably if you go in the Chinese chip-expos with a purchase-order for thousands of chips, you can buy all you want. There isn't any market for single chips. They rarely fail, and keyboards are now so cheap that when the taco-crumbs clog the keys, we just go buy another.

Cheap keyboards are really cheap. NewEgg has at least 10 under $10.
http://www.newegg.com/Keyboards/SubCategory/ID-63
With some hunting you can find keyboards near $2.

Also most PC geeks have a pile of excess keyboards. For your purposes they can be in pretty bad shape.

[derevaun]

Digispark does it--but with four available switches. Otherwise, the USB part is taken care of in software. You just need to debounce and designate which character to send to the computer, for a given switch.

[WyndBalduram]

Thanks everyone, for all the feedback.  I did not realize when I first had this idea what would actually be involved in order to do it from scratch.  I am thinking of simply hacking a keyboard for my own personal use, to start, and then, when I have some funds to throw around, I will look into getting one of these microprocessor programmers.

I have worked mostly with non microprocessor chips when building stomp boxes, and have honestly avoided looking into them for fear that they would be way over my head.

[Jdansti]

if you're trying to interface between your foot and a computer, why not use MIDI?

[deadastronaut]

go cheap and simple...it works. ...i will hack this myself one day, and box it up with big buttons.

http://www.youtube.com/watch?v=VxaClh7FACw

[symo]

Digispark does it--but with four available switches. Otherwise, the USB part is taken care of in software. You just need to debounce and designate which character to send to the computer, for a given switch.

Does anyone have a build tutorial link for using with Youtube and VLC as a foot controller using some decent footswitches?  Looks good, my soldering skills are good but the programming side of me is not all that.  So any links would be useful.  Would be looking to do a play/pause, fastfwd, rwd type thing.