custom usb keyboard

[kutalinelucas]

hi guys. I have a little project in my head but im not sure how to go about a part of it.

i need to figure a way of making a 32 button usb (or bluetooth) keyboard. I cant hack an existing keyboard because of the size of the matrix involved, and 32 inputs into a processor seems quite excessive. The other problem is the keypresses arn't mechanic so i couldn't just design a smaller matrix.
i'm not an electronic genius, but I'm more than willing to read up on everything if i could just get a nudge in the right direction.

thanks

 

[Nigel Goodwin]

You don't need 32 inputs, keys are matrixed, so a 6x6 matrix (36 keys) requires only 12 inputs.

Your problem isn't reading the keys, it's the USB interface - I've no idea how it's implemented in a keyboard.

Probably the only sensible way is to buy a USB keyboard and strip the insides out of it, add your own smaller keyboard to the processor inside it.

 

[kutalinelucas]

a bit of logic needed?

hi.
I was wondering if anybody can help, but its difficult to explain.

I have five push switches going into a circuit. i would like to delay taking the state of the switches (ie weather they are being held down or not) untill one of the held buttons is released, when their logic state is sent to the next stage of the circuit.

The (button) inputs are reset. it should start again when all buttons have been released.

Im not sure weather i'm asking alot or it's fairly simple! Any help be really appriciated.

 

[shaneshane1]

Could you explain in a little more detail,eg what do the switches do, and what sort of switches they are, eg momentary?

 

[kutalinelucas]

its a usb glove keyboard - a push switch on each finger.

32 possible combinations, the first 26 for the a;phabet and the other 6 for other control such as space etc...so for instance if you depress the thumb and forfingers buttons the character 'A' would apper in a word application.

im not sure which way to go with the rest: either into a 5 - 32 line decoder, 6x6 matrix and hack the processor and usb port etc from a usb keyboard or just a 5 bit input straight into a processor, but then i'd have to learn asm and create a custom driver, but the other method requires lots of components.

Just knowing how to delay/reset the inputs would be a fantastic start.

any suggestions?

 

[kutalinelucas]

the switches would probably be similar action to a normal keyboard

 

[eblc1388]

Your problem is to determine when exactly is the "wanted" user input key value.

No one can press all the keys simultaneously so they will be pressed one after another or severals at a time. As such you should not process the temporary data as valid until there is no more changes from the user. Then the input can be converted to actual key values or key scan codes using a lookup table. This can be easily done using a microcontroller but is a little bit difficult using logic gates or decoders alone as you still need to work on the USB interface.

I'm not sure if USB keyboard outputs key scan codes or simply ASCII values but I'm sure other forum user will tell you.

If you don't like asm programming, I would say you will need a microcontroller with USB connection capability, and programming in C.