Re: keypad scanner
- From: Jim Granville <no.spam@xxxxxxxxxxxxxxxxx>
- Date: Fri, 03 Jun 2005 18:28:51 +1200
praveen.kantharajapura@xxxxxxxxx wrote:
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
Homework ?
You will need Opendrain OPs on drivers, and pullups on IPs.
exercises: a) If you use a MATRIX, what are the sense limits on multiple key presses ? Start by considering 4 closed keys, one in each corner.
b) Would a user find 0-192ms slow/erratic on a keypad response ?
-jg
.
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