Debouncing the SX/B Example of Keypad in the help file?
Brian Carpenter
Posts: 728
Can anyone point me in the right direction for debouncing the kepad example in the SX/B help file
This is the pertinate code snippet i believe.· I know that i need to sample the value and make sure that i get the same value for atleast a 2 cycles.·
Any body done this before?
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GET_KEY:
tmpB1 = 0 ' reset keyboard value
Keys = %0000_0111 ' activate first row
TRIS_Keys = %1111_0000 ' refresh IO state
PLP_Keys = %0000_1111 ' pull-up input pins
FOR tmpB2 = 1 TO 4 ' scan four rows
IF Col1 = Yes THEN EXIT ' check buttons on column
INC tmpB1 ' update key value
IF Col2 = Yes THEN EXIT
INC tmpB1
IF Col3 = Yes THEN EXIT
INC tmpB1
IF Col4 = Yes THEN EXIT
INC tmpB1
Keys = Keys >> 1 ' select next row
Keys = Keys | %0000_1000 ' clear previous row
NEXT
RETURN tmpB1
This is the pertinate code snippet i believe.· I know that i need to sample the value and make sure that i get the same value for atleast a 2 cycles.·
Any body done this before?
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It's Only A Stupid Question If You Have Not Googled It First!!
Comments
Although not the exact subroutine he mentions, there is similar source code is in the TUT019.src file in the downloads section.
It's basically checking the bit, delaying (typ 20-30msec), and see if it's still pressed after the delay.
Here's an interesting link with some higher level examples.
http://www.ganssle.com/debouncing.pdf
...or Google "switch debounce software" [noparse]:o[/noparse])
Rodney
I would try something like this:
KeyChanged = 0 ' Initialize Key Change bit variable. FirstKey = GET_KEY ' Remember the First Key value seen. For i = 1 to 5 ' Loop to debounce keypad inputs. theKey = GET_KEY ' Get the current keypad value. If theKey <> FirstKey Then ' Detect keypad changes. KeyChanged = 1 ' Indicate that a key has changed. EndIf Next i ' Repeat If KeyChanged = 1 Then ' Detect keypad changes and... theKey = 16 ' Treat it as if no key was pressed. EndIfYou will need to declare i and FirstKey as byte variables and KeyChanged as a bit variable.
- Sparks
GET_KEY: lastKey = $FF DO tmpB1 = 0 ' reset keyboard value Keys = %0000_0111 ' activate first row TRIS_Keys = %1111_0000 ' refresh IO state PLP_Keys = %0000_1111 ' pull-up input pins FOR tmpB2 = 1 TO 4 ' scan four rows IF Col1 = Yes THEN EXIT ' check buttons on column INC tmpB1 ' update key value IF Col2 = Yes THEN EXIT INC tmpB1 IF Col3 = Yes THEN EXIT INC tmpB1 IF Col4 = Yes THEN EXIT INC tmpB1 Keys = Keys >> 1 ' select next row Keys = Keys | %0000_1000 ' clear previous row NEXT IF tmpB1 = lastKey THEN EXIT PAUSE 20 lastKey = tmpB1 LOOP RETURN tmpB1Here is how I would do it. Adjust the PAUSE value as needed.·NOTE this is untested code [noparse];)[/noparse]
Bean.
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Cheap used 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com
"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
I have used Bean's Code and also Sparks - R - Fun
I cant get the desired results
What i am trying to make it do:::
If TheKey = LastKey loop until it does not As soon as it does not.· Return the new value that does not match
For instance.... if no key is pressed, TheKey will be 16 and will continue to be 16 while nothing is pressed.
Now this is where it gets a little tricky
As soon as a key is pressed. Lets say 3.··· The 'TheKey' value has changed but i dont want it to be returned until 'TheKey' = 16 again. meaning that the button was released.
·So once the key is released it will return '3' in the 'TheKey' value.· and then it will continue returning 16 until another key is RELEASED
Any ideas on how this can be done?
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It's Only A Stupid Question If You Have Not Googled It First!!
Post Edited (altitudeap) : 11/6/2006 5:29:40 AM GMT
key VAR Byte oldKey VAR Byte ' Temp used by GET_KEY routine tmpB1 VAR Byte ' Temp used by GET_KEY routine lastKey VAR Byte ' Used by GET_KEY routine, DO NOT USE IN MAIN CODE thisKey VAR Byte ' Used by GET_KEY routine, DO NOT USE IN MAIN CODE Start: lastKey = 16 DO key = GET_KEY IF key <> 16 THEN ' Do whatever ENDIF ' Do other processing LOOP END GET_KEY: oldKey = $FF DO tmpB1 = 0 ' reset keyboard value Keys = %0000_0111 ' activate first row TRIS_Keys = %1111_0000 ' refresh IO state PLP_Keys = %0000_1111 ' pull-up input pins FOR tmpB2 = 1 TO 4 ' scan four rows IF Col1 = Yes THEN EXIT ' check buttons on column INC tmpB1 ' update key value IF Col2 = Yes THEN EXIT INC tmpB1 IF Col3 = Yes THEN EXIT INC tmpB1 IF Col4 = Yes THEN EXIT INC tmpB1 Keys = Keys >> 1 ' select next row Keys = Keys | %0000_1000 ' clear previous row NEXT IF tmpB1 = oldKey THEN EXIT PAUSE 20 oldKey = tmpB1 LOOP thisKey = tmpB1 IF thisKey = 16 THEN IF lastKey <> 16 THEN thisKey = lastKey lastKey = 16 RETURN thisKey ENDIF ENDIF lastKey = thisKey RETURN 16Try this...
Bean.
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Cheap used 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com
"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
This is what i now have.
DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX FREQ 4_000_000 ' ------------------------------------------------------------------------- ' IO Pins ' ------------------------------------------------------------------------- Keys VAR RC ' keyboard scan port TRIS_Keys VAR TRIS_C PLP_Keys VAR PLP_C Col1 VAR Keys.7 ' column inputs Col2 VAR Keys.6 Col3 VAR Keys.5 Col4 VAR Keys.4 Restart Var RA.1 ' ------------------------------------------------------------------------- ' Constants ' ------------------------------------------------------------------------- Yes CON 0 ' active low input No CON 1 ' ------------------------------------------------------------------------- ' Variables ' ------------------------------------------------------------------------- theKey VAR Byte ' from keypad, 0 - 16 oldKey VAR Byte ' Temp used by GET_KEY routine row VAR Byte ' keyboard scan row tmpB1 VAR Byte ' subroutine work vars tmpB2 VAR Byte tmpW1 VAR Word VendStatus Var Word VendAmm Var byte (16) i Var byte LastKey VAr byte key VAR Byte ' ========================================================================= PROGRAM Start ' ========================================================================= ' ------------------------------------------------------------------------- ' Subroutine Declarations ' ------------------------------------------------------------------------- GET_KEY SUB 0 ' get key from pad DELAY SUB 1, 2 ' delay in milliseconds ' ------------------------------------------------------------------------- ' Program Code ' ------------------------------------------------------------------------- Start: lastKey = 16 PUT vendAmm, 25, 25, 25, 25, 25, 25, 25, 25, 25, 20, 20, 20, 15, 15, 10, 10 Main: DO key = GET_KEY IF key <> 16 THEN IF key < 16 THEN tmpB1 = 1 SHL Key ENDIF tmpW1 = 1 SHL Key DEC VendAmm(key) IF vendAmm(key) = 0 THEN VendStatus = VendStatus OR tmpW1 ENDIF '---------Reseting the Flags that indicate empty vend merchandise ENDIF Break IF Restart = 0 then goto start Endif LOOP END ' ------------------------------------------------------------------------- ' Subroutine Code ' ------------------------------------------------------------------------- ' This routine works by activating each row, then scanning each column. ' If a particular row/column junction is not active (pressed), the key ' value is incremented and the scan continues. As soon as a key is found, ' the routine exits. If no key is pressed the routine will exit with a key ' value of 16. GET_KEY: oldKey = $FF DO tmpB1 = 0 ' reset keyboard value Keys = %0000_0111 ' activate first row TRIS_Keys = %1111_0000 ' refresh IO state PLP_Keys = %0000_1111 ' pull-up input pins FOR tmpB2 = 1 TO 4 ' scan four rows IF Col1 = Yes THEN EXIT ' check buttons on column INC tmpB1 ' update key value IF Col2 = Yes THEN EXIT INC tmpB1 IF Col3 = Yes THEN EXIT INC tmpB1 IF Col4 = Yes THEN EXIT INC tmpB1 Keys = Keys >> 1 ' select next row Keys = Keys | %0000_1000 ' clear previous row NEXT IF tmpB1 = oldKey THEN EXIT PAUSE 20 oldKey = tmpB1 LOOP thekey = tmpB1 IF thekey = 16 THEN IF lastKey <> 16 THEN thekey = lastKey lastKey = 16 RETURN thekey ENDIF ENDIF lastKey = thekey RETURN 16 ' ------------------------------------------------------------------------- ' Use: DELAY ms ' -- 'ms' is delay in milliseconds, 1 - 65535 DELAY: IF __PARAMCNT = 1 THEN tmpW1 = __PARAM1 ' save byte value ELSE tmpW1 = __WPARAM12 ' save word value ENDIF PAUSE tmpW1 RETURNMan i love the SX Debug feature.· As i press and hold the button i can see that the SX has noticed the state change of the switch and then just as i release it, it DEC the value in associated register.· What i cant seem to make it show me is the··Value for VendStatus.· Should i be able to see that in the register somewhere.· Maybe my code is not making the bit in the associated location go high.·· ie if the value in register 2 goes to 0 the Value in VendStatus should be 0000_0000_0000_0100
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It's Only A Stupid Question If You Have Not Googled It First!!