Switch Debouncing Program
Switch Interfacing & Debouncing
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Over here we consider ONE Switch & TWO LED connected to a microcontroller. Please check the SWITCH INTERFACING and the LED INTERFACING article to see how to connect Switches & LED’s to a microcontroller.
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Here is a program that will TURN ON A LED1 if a switch is debounced properly & will TOGGLE LED2 if there is some error in switch debouncing. LED1 will be ON until the switch is pressed & will turn OFF as soon as it’s released. We have taken the debounce period as 20ms. So once a LOW signal has been received from the switch the controller will again check the switch status after 20ms & if at that time the switch is high LED2 will be toggled and if the switch is LOW LED1 will be turned ON.
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led1
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bit |
P2.0 |
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led2
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bit |
P2.1 |
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switch1
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bit |
P1.0 |
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ORG 0000h
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setb switch1
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//initialize switch 1 as input |
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setb led1
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//Turn OFF LED1 |
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setb led2
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//Turn OFF LED2 |
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wait:
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jb switch1,wait
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// Wait till switch1 has been pressed |
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call debounce_delay
jb switch1,c1_wait
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//After debouncing period, switch is low hence switch succesfully debounced
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clr led1
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//Turn ON LED1 |
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jnb switch1,$
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//wait till switch has been released |
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setb led1
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//Turn OFF LED1 |
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ajmp wait
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c1_wait:
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//Switch PIN high after debounce period so error in debouncing
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cpl led2
ajmp wait
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debounce_delay:
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//Subroutine for generating 20ms delay |
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mov r7,#245
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l1_debounce_delay:
mov r6,#40
djnz r6,$
djnz r7,l1_debounce_delay
ret
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END
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Written by Administrator
Administrator
Administrator
