On a sunny day (Thu, 24 Apr 2008 08:43:33 -0400) it happened Fred Bloggs wrote in :
That is very negative, ungrounded... This sort of thing is what you see in TV quizzes. In fact I remember a company that did something like that with Siemens PLCs, each person had a light bulb too, to show he / she pressed a button. It was _very_ expensive :-)
I've done this before (n-key rollover), with a 6502. These days I'd have to program an FPGA with a 6502 core and invest in an EPROM for the s/w. Or, I could do the whole thing in the FPGA, or even design it in "discrete" (i.e., chip-level) logic. I categorically refuse to have anything to do with a PIC, because bank-switching is intrinsically evil.
I'll be happy to design and build the whole circuit for you, and submit it to your instructor under your name, for one easy payment of only $10,000.00. :-)
Let me know! Rich (If you want to email me, take my yahoo spamdump, snipped-for-privacy@yahoo.com, and elide ard.)
If you don't already know these answers, you're in the wrong class.
Good Luck! Rich
Good Luck! Rich
Funny. I've been using PICs for years and never had to worry about bank switching. There are these wonderful things called C compilers that take care of stuff like that for you. And if you don't like the PIC, there are a dozen other 8 bit micros to choose from.
An FPGA is ridiculous overkill for something like this. And those darn BGA and other large pincount FPGA packages are intrinsically evil too. Also, having to have an external FLASH chip to program your FPGA at boot up is intrinsically evil too. The FLASH cell based Actel devices are at least a step forward.
Dave.
--- What do you mean by "at the same time"?
In your application it's not at all likely that two or more switches will be turned on at exactly the same time, so you need to specify a "window" in time during which, if multiple switch closures occur, they will be considered as having occurred simultaneously.
That is, if you have two switch closures occuring within one tenth of a second, would you consider that simultaneous?
One one-hundredth of a second?
One one-thousandth?
One one-millionth?
?What I'm envisioning is a system with timing like this:
____________ ____________ ____________ WINDOW___| |_____| |__| |___ ___________________________________________________ S2_______| ________________________________ S4__________________________| ________________________ S1__________________________________| ________________ S3__________________________________________|
where the window would be generated by any switch closure firing a non-retriggerable one-shot and the display indicating which switches had been made during that window. Additionally, the display would put spaces between captured closures, so the display would indicate, for the instance above: 2 41 3
How many switches do you have and what width window do you need?
Better yet, what's your application, how many switches do you have and what width window do you need??
JF
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