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???
05/29/06 07:55
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 		 #117214 - watch human reaction speed
Responding to: ???'s previous message
Jeroen Wilbers said:
I know normally you keep scanning it but I do want it to react when I pres a key.



Whats wrong to spend less than 1% of CPU load to scan a keyboard e.g. every 20ms inside the timer interrupt ?

No human was able to detect a delay of only 20ms !


Immediately on the human view means reaction within 100..300ms.

Immediately on a Windows user view means reaction within 5s.


So only 10..50ms scanning interval are sufficient in any case.


Peter



List of 28 messages in thread
TopicAuthorDate
passive matrix keyboard readout            01/01/70 00:00      
   yep use the dallas switch debouncers            01/01/70 00:00      
      really, you can't have it both ways            01/01/70 00:00      
   Keypad            01/01/70 00:00      
      what???long weekend maybe            01/01/70 00:00      
         dedicated HW in some '51s            01/01/70 00:00      
   watch human reaction speed            01/01/70 00:00      
   derivative with interrupt on pin change            01/01/70 00:00      
      Or use a maxim 6816            01/01/70 00:00      
         I use SW debouncing...            01/01/70 00:00      
   Can reduce time spent in ISR Key Scan            01/01/70 00:00      
   Use tiny slave micro            01/01/70 00:00      
      Makes sense!            01/01/70 00:00      
         Programming the slave micro            01/01/70 00:00      
            $0            01/01/70 00:00      
               Non-zero cost            01/01/70 00:00      
                  who cares            01/01/70 00:00      
                     The folks who pay will care            01/01/70 00:00      
                        You apply what I said about apples to or            01/01/70 00:00      
                           you missed my meaning            01/01/70 00:00      
                              OK, I'll clarify            01/01/70 00:00      
            Costs? He needs to solve it anyway...            01/01/70 00:00      
               Tme is money            01/01/70 00:00      
                  contradictory            01/01/70 00:00      
         Key bounce.            01/01/70 00:00      
            use a LPC            01/01/70 00:00      
               any MCU will work            01/01/70 00:00      
                  with a LPC you can do either            01/01/70 00:00      

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