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#3714008 - 01/08/13 04:11 PM HELP: Arduino UNO board matrix - is this possible?  
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iam73 Offline
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iam73  Offline
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Hi guys,

Does anyone know if it's possible to create a matrix from a small Arduino UNO board to somehow multiply to number of digital inputs?

The stock board has 14 inputs. I was wondering if a matrix could let the board offer more inputs - the same way its done with the bu0836 matrix or even better, with the BU0836x matrix (http://simhq.com/forum/ubbthreads.php/topics/3366327/1.html)

I get the concept that windows would/should still see the stock number of inputs, i.e. 14, but since the matrix would create combos, the mapping software should be able to handle those combos (i.e. button 1+2, button 1+3....) pretty much the same way jimbop did it with his bu0836x...

Possible ?

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#3714021 - 01/08/13 05:01 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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f15sim Offline
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Graham, WA
You can create a matrix of switches by diode isolating them - it may however be easier for you to just purchase a Centipede Shield from Macetech. Each one supports 64 digital inputs and you can use two of them on one Arduino.

g.


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#3714025 - 01/08/13 05:16 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: f15sim]  
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iam73 Offline
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Originally Posted By: Gene Buckle
You can create a matrix of switches by diode isolating them - it may however be easier for you to just purchase a Centipede Shield from Macetech. Each one supports 64 digital inputs and you can use two of them on one Arduino.

g.


Thanks Gene. Very interesting, although the reason I asked about matricing the UNO board is that I'm on a tighter than tight budget and a friend just switched to a mega board and he offered me his UNO. I don't mind really working out the matrix, if it works, all the better.

So basically, am I right assuming that any controller/gamepad board can be turned into a diode isolated matrix to "multiply" the number of switches that can be used with it?

#3714027 - 01/08/13 05:23 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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f15sim Offline
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Graham, WA
No - the hardware has to be designed to use a diode isolated matrix. There are examples out there on how to do this with the Arduino. AFAIK there's also firmware out there that will make the Uno appear to be a standard USB joystick.

g.


Proud owner of 80-0007
http://www.f15sim.com - The only one of its kind.
http://geneb.simpits.org - the Me-109F/X Project
#3714030 - 01/08/13 05:39 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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iam73 Offline
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Thanks Gene, very informative.

#3714457 - 01/09/13 02:22 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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iam73 Offline
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iam73  Offline
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Hi Gene, or anyone else (knowledgeable wink )

Regarding matricing a board, while reading information on different solutions, I found this on the generichid website and was wondering if it applied to any board wired up in a matrix or just the ones supported by generichid (i.e. atmel or teensy++):

"Because of the shared nature of the key matrix, there is a restriction on how many keys can be pressed simultaneously. If two keys on different rows and different columns are pressed, no key will be shown as pressed. The key matrix is best used when it makes sense that only one key is pressed at the same time. If a button is required to be on all the time (toggle switch), or just a button that needs to be used in combination with others, a regular button should be used."

I read the posts on the bu0836 and bu0836x matrix but never seen such warning about simultaneous button press for those board.

So does this "matrix limitation" applies to any boards using a matrix? In other words, it would mean a matrix is perfect to get lots of "momentary" inputs, but isn't a good solution for "always-on" switches, such has on/on or rotaries, am I right?

Or, is this why diodes are required, to overcome this "limitation" ?


(P.S. I know I could go the easy route and get that arduino button shield, but part of the fun for me with my humble project is to learn new stuff and understand the inner working of electronics)


Last edited by iam73; 01/09/13 02:41 PM.
#3714488 - 01/09/13 03:08 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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f15sim Offline
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Graham, WA
Well the idea behind a diode-isolated matrix is to close as many of the switches as you like and still be able to test individual switches for closure. A PC keyboard is an example of a non-isolated matrix. It can't decode more than 3 or 4 keys at one time.

Here's an example I drew up about a decade ago:

http://www.simpits.org/fileproc/dload.php?file=ematrix.png

The nomenclature is EPIC specific, but just call the lines marked "DB0..DB7" as "rows" and the lines marked as "Mod 1 Row 0", etc as "columns". By positioning the diodes as shown on the schematic, you can "decode' every individual switch in the matrix. Any diode would work, but a 1N4001 makes a great choice. They're dirt cheap and can be found everywhere.

You might want to check out this project as well:
http://arduino.cc/blog/2012/05/14/unojoy-a-usb-joystick-for-mac-pc-linux-or-ps3/

GenericHID is a fantastic tool for cockpit builders - where did you find that quote you pasted in? I didn't find it on his website.

g.


Proud owner of 80-0007
http://www.f15sim.com - The only one of its kind.
http://geneb.simpits.org - the Me-109F/X Project
#3714507 - 01/09/13 03:39 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: f15sim]  
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iam73 Offline
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Originally Posted By: Gene Buckle


GenericHID is a fantastic tool for cockpit builders - where did you find that quote you pasted in? I didn't find it on his website.

g.


Hi Gene, thanks again for great info, I'll read all of it during lunch break. I did find the unojoy page earlier today and its great!

Here's where the "limitation" is mentioned on the GHID website:
http://generichid.sourceforge.net/keymatrix.htm

I got there from that page, where all "tools" are described: http://generichid.sourceforge.net/generichid.htm

The website doesn't mention anything about using diodes with the key matrix - that may explain the warning - or maybe they are assuming one would press multiple keys on a keypad simultaneously, not sure - but they do mention that this matrix isn't fit for multiple button presses.

Cheers!


Last edited by iam73; 01/09/13 03:40 PM.
#3733770 - 02/11/13 02:55 PM Re: HELP: Arduino UNO board matrix - is this possible? [Re: iam73]  
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PropNut Offline
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Just to chime in, not on the matrix but the excellent source that Generichid is. I use it in my Mechpit with a Teensy++2.0 controller board. Allows me to program my Teensy to be whatever I like, rotories, buttons, keyboards, Joystick axis', etc. And it lets me program a unique name for each component that I add (just ordered two more Teensy++2.0 boards).


F/A-18C Hornet cockpit build project:

http://hornetpits.org/index.php?topic=15.0

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