25, or 4 to 6 [Not Chicago Content]
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01-29-2015, 11:06 PM
Post: #5
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RE: 25, or 4 to 6 [Not Chicago Content]
(01-29-2015 06:06 PM)PANAMATIK Wrote: Getting 6's instead of 4's is strange because these keys are in different keyboard columns, there might be some contact or smear, that has to be removed between the columns. Good point, Bernhard - when I take it to bits to clean it, I'll take a close look at that row. (01-29-2015 06:06 PM)PANAMATIK Wrote: Each row, these are the horizontal five keys from left to right, is scanned every 308 microseconds. After 7 rows, that is after 2,1 ms, all keys are read. If a key is pressed, the voltage of the column goes from 6.4V either to 0V or to a midrange voltage about 3,5V , if the LED display segment is on, that is displayed with the same row as the keyboard. In my ACT chip I read the keyboard columns by its analog values, because they can have three different levels. Thanks for that - although I don't have much test equipment myself these days, I can always borrow a scope in one of the labs at work. By "kill the display" I mean that the display goes dark, which suggests to me that keyboard/display scanning has stopped. I'll give it a clean with DEOXIT Gold - chances are, that will fix it (fingers crossed!). --- Les [http://www.lesbell.com.au] |
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