Debouncing the SX/B Example of Keypad in the help file?

Brian Carpenter · 2006-10-24 17:33

Can anyone point me in the right direction for debouncing the kepad example in the SX/B help file

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!!

Yendor · 2006-10-24 19:25

Have you checked out Gunther's Book? See pgs 99/100. It's in assembly but you should get the drift.

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

Sparks-R-Fun · 2006-10-24 19:37

Altitudeap,

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.
    EndIf

You will need to declare i and FirstKey as byte variables and KeyChanged as a bit variable.

- Sparks

Bean · 2006-10-24 21:28

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 tmpB1

Here 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
·

Brian Carpenter · 2006-11-06 05:14

Ok guys,· Thanks for all the help thus far.

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

Bean · 2006-11-06 13:40

 
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 16

Try this...

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
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
·

Brian Carpenter · 2006-11-07 04:53

Thanks Bean

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
  RETURN

Man 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!!

Brian Carpenter · 2006-11-08 03:59

ok Great News. I used the Watch VendStatus,16,UBIN And it works. This Debug is cool

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It's Only A Stupid Question If You Have Not Googled It First!!

Debouncing the SX/B Example of Keypad in the help file?

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