foobarecho
Posts: 18
Joined: Tue Aug 06, 2013 4:56 am

Cannot press three keys at the same time

Tue Aug 13, 2013 11:23 am

Not sure if this is raspbian problem, keyboard problem, openmsx or emulationstation problem.

so asking here to see if someone dealt with this problem before and can help.

it seems that the software cannot detect three different keys pressed at the same time. for example if I press up and left arrow to go diagonally and then press space, space key is not registered, unless I remove my hand off one of the arrow keys.

how to solve this? and which software responsible for this.

thanks

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pluggy
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Location: Barnoldswick, Lancashire,UK
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Re: Cannot press three keys at the same time

Tue Aug 13, 2013 12:11 pm

I'd suspect the USB driver / implementation. Make sure you're using the latest / updated OS since they've made a lot of improvements in the USB arena lately. Its ongoing, you could try wading through http://www.raspberrypi.org/phpBB3/viewt ... 28&t=39175 it will give you a flavour of what they are doing.
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

PiGraham
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Re: Cannot press three keys at the same time

Tue Aug 13, 2013 12:25 pm

How are you reading the keyboard.

On my Win 8 PC I can't type space characters while holding up and left cursor keys.

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jojopi
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Re: Cannot press three keys at the same time

Tue Aug 13, 2013 12:55 pm

It is the keyboard. Key switches are wired at the intersections of signal lines called rows and columns. When you press three keys that are corners of a rectangle, the key at the fourth corner of the rectangle also appears to conduct. Both the third and fourth keystrokes must be suppressed because the hardware cannot tell which one is real. See: http://www.dribin.org/dave/keyboard/one_html/

More expensive gaming keyboards include a diode for each switch to prevent the phantom current paths. USB HID protocol allows the keyboard to report up to six keys, plus eight modifiers, pressed together.

To reduce the problem on regular keyboards, you should include the ability to change the controls to keys that do work together. The modifier keys, Shift Ctrl Alt Super, are much less likely to clash than others.

foobarecho
Posts: 18
Joined: Tue Aug 06, 2013 4:56 am

Re: Cannot press three keys at the same time

Wed Aug 14, 2013 6:17 am

Thanks a lot for the help. I confirm Jojopi is right. turned out the keyboard. I used an older Dell keyboard, maybe it works that way because it has a built-in usb hub. I wonder if that limits the ability of USB connector.

I tested with MS keyboard from another computer and it worked fine. I'll get a bluetooth adapter, hopefully my bluetooth keyboard behaves correctly.

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