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keypad scanner

Hi all,

I am implementing a 6x6 matrix keypad scanner in CPLD. My requirment is i should detect multiple key presses also. What i am planning to do is , i will scan the rows (6 of them sequentially) , when all the 6 rows are scanned i will send the 36 bit output(each bit corresponds to each individual key .'0' indicates pressed)to the controller.The scan rate for each row is approximately

32 msec , so every 32x6=192 msec i will be sending the 36 bit code to controller(HCS12).

I want your comments on this implementation in CPLD.

Regards, Praveen

Reply to
praveen.kantharajapura
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That's way too slow a scan rate.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
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Reply to
Spehro Pefhany

Why the specification for a "Complex programmable logic device"? Is a microcontroller out of the question? That is a programmable logic device, and typically fairly complex, so it _would_ fit your spec, and implementing something like your app in firmware would be a snap - doing it with a big registered gate array would be a freaking nightmare, IM!HO.

Or, just scan it with the contoller itself. What's an "HCS12?"

You can get microcontrollers, like the PIC, that have 16 I/O lines, which would give you 12 for your scanner, and 4 more for data with handshaking. I'm not a PIChead, so have no idea which of the vast family you'd want to choose, but someone here will surely help out in that respect.

Some also recommend AVRs or Basic Stamps - any of these could do the job.

Good Luck! Rich

Reply to
Rich Grise

Probably a homework question from an Indian university.

Successor to the Motorola HC11, from Freescale. They've changed the numbering system a bit... now they have numbers like MC9S12.. Scanning a keyboard would use negligible processing power of any of that series.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

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