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1  Using Arduino / Project Guidance / Re: need an estimate of time required to scan 11x8 matrix on: January 18, 2013, 07:15:02 pm
Thank you everyone for your input.

This is an attempt to hack a electronic soft tip dartboard.  Research on the internet indicates that the pulse could be as little as 1ms and as much as 4ms.  Hard thrown darts sometime cause false readings in some false sectors.  It is possible that i will find simply ignoring any other switch closures past the initial detection with a delay will be effective.  I suspect that no the hit sector would always be closed first before any other chatter on other sectors would occur.  I will find out with testing and experimentation.  The reason I ask the original question is that I have not yet purchased the board, and I don't want to go thru to process of doing this and fail due to hardware limitations.  After I determine a dart has registered, I will send the information to a pc by emulating an usb keyboard, where the input will be used by an external program.

So in short, It sounds like this should work.  My plan would be to set all outputs low and use the chip pullups on the inputs.  Continuously scan the inputs, upon detection, start setting the outputs high one at a time and recheck the input for a change in status.  Once found, delay(possibly) set all outputs high except the active pin, and re query inputs to confirm correctness.  So, from the initial detection to the confirmation i need to be under 1ms.  Data intperpretation and transfer can be handled afterwards easily.  After 1 second delay or so, the whole thing resets and stars over.

Any further conformations or opinions about my plan would be appreciated.  If the opinion is that it isnt fast enough, I will look into a faster board, such as an arduino due.

Thanks, Mike
2  Using Arduino / Project Guidance / Re: PH fish tank on: January 18, 2013, 06:33:19 pm
I actually did this some years ago.  I started out with an arduino, but ended up doing this with x-10 modules and a set-point ph monitor.  The monitor sent a signal to the x-10 wall module, which was sent over the home wiring to a usb wall outlet receiver and finally to the computer.  I used a wall x-10 wall receptacle to plug a surplus medical dosing pump into to deliver the carbonate.  The whole thing was programmed and controlled by (I forget the name) x-10 software.  I got the idea and instructions from someone else on  The discussion is probably archived.

3  Topics / Device Hacking / Re: Project idea (dart board interface) on: January 17, 2013, 01:53:26 am
I am working on the same thing.  I plan to use an arduino micro to decode the 8x11 input matrix.  I am trying to determine if I can write instructions to scan the matrix for hits quickly enough to register the quickest dart hits.  Approximately 1ms should catch nearly every hit.  A reference time from another matrix scanning board would be helpful
4  Using Arduino / Project Guidance / Re: Guitar Fret Sensing on: January 16, 2013, 10:03:28 pm
I believe the typical midi setup seems the frequency & amplitude at each individual string
5  Using Arduino / Project Guidance / Re: need an estimate of time required to scan 11x8 matrix on: January 16, 2013, 08:29:59 pm
I am unfamiliar with how i could get the time used by using the library

6  Using Arduino / Project Guidance / Re: need an estimate of time required to scan 11x8 matrix on: January 16, 2013, 07:19:19 pm
This functions exactly like a standard keyboard matrix,  I the need to detect and identify the switch the closed for the 88 possible switches (only one switch will be actuated at a time) in under 2ms, as their closure time could be as little as that.   So, the polling cycle needs to be less than 2ms.  I would do this with pull ups on the output side.
7  Using Arduino / Project Guidance / need an estimate of time required to scan 11x8 matrix on: January 16, 2013, 06:45:19 pm
I want to use an adriuno micro to scan a 8 x 11 matrix.  i need to do this in under 2ms, maybe 1ms, possibly including debounce.  I am a noob.  About how much time will it take to do this scan?

Thanks, Mike
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