Switch Logic Design

Comments

• doggiedoc Posts: 2,250

  2011-02-05 06:18 edited 2011-02-05 06:18

  I would think that SELECT...CASE routine using %00, %01, %10, and %11 would suit this nicely.
  
  I'll post an example shortly....
  
  Paul
• doggiedoc Posts: 2,250

  2011-02-05 07:00 edited 2011-02-05 07:00

  I can't find the original article at the moment. But Jon Williams (JohnnyMac) wrote a Nuts & Volts article a while back about debounceing button inputs that would translate nicely for your application of switches.
  
  Below is a portion of some code I wrote with his help. I've generalized it for you so it may not run as typed and it reads 4 inputs instead of just 2.
  

  ' [----------------------------------------------------------------------------]
  '                          [-- I/O  Definitions --]
  ' [----------------------------------------------------------------------------]
  SwtchInputs         VAR   IND   'pins 12,13,14,15 to read switch inputs
  
  
  
  ' [----------------------------------------------------------------------------]
  '                             [-- Variables  --]
  ' [----------------------------------------------------------------------------]
  
  
  theSwitches         VAR   Nib
  swtchCounter        VAR   Nib
  
  
  
  ' [----------------------------------------------------------------------------]
  '                            [-- Program Code --]
  ' [----------------------------------------------------------------------------]
  
  Main:
  
      DO
  
        GOSUB Get_Switches
           
        SELECT theSwitches
          CASE %1000
            GOSUB Do_Something_A
          CASE %0100
            GOSUB Do_Something_B
          CASE %0010
            GOSUB Do_Something_C
          CASE %0001
            GOSUB Do_Something_D
          ENDSELECT
  
       LOOP
    END
  
  
  
  ' [----------------------------------------------------------------------------]
  '                            [-- Subroutines  --]
  ' [----------------------------------------------------------------------------]
  
  Get_Switches:
    theSwitches = %0000
    FOR swtchCounter = 1 TO 5                   'loop to debounce the inputs
        theSwitches = ~theSwitches & SwtchInputs
    NEXT
    RETURN
  
  Do_Something_A:
     ' your code here
    RETURN
  
  Do_Something_A:
     ' your code here
    RETURN
  
  Do_Something_B:
     ' your code here
    RETURN
  
  Do_Something_C:
     ' your code here
    RETURN
  
  Do_Something_D:
     ' your code here
    RETURN
  
  
  

  
  
  Here's a link to a post with my full original code.
  
  Perhaps smarter people will chime in soon!
  
  Paul
• MStein Posts: 9

  2011-02-06 15:23 edited 2011-02-06 15:23

  Thank you...
• bsnut Posts: 521

  2011-02-06 18:05 edited 2011-02-06 18:05

  Are you trying to look at a Encoder that is attached to a shaft? If, this is correct an encoder program will work perfect and it will do what you are looking for. This program can be found it in the Stamp Works PDF, which is on the Parallax website.
• Unsoundcode Posts: 1,532

  2011-02-06 18:52 edited 2011-02-06 18:52

  Hi , when your program makes the first comparison ( IF instruction ) if it is true then the following comparisons will all be false. Seeing the second comparison as false the program flow will exit to the endif 's and repeat the loop. When the switches change state and the first comparison becomes false the program flow will exit to the endif 's and repeat the loop. In other words the second and third comparisons can never be seen as true.
  
  You will probably need to debounce the switch inputs ( see them in a certain state for a set length of time ) . At first glance and not knowing exactly how the switches operate my inclination would be to just do two checks , the first would be both switches at logic level 1 , seeing this state I would move on and wait for a change in either bit 0 or bit 1 , whichever went low would indicate direction. Once direction is determined go back to looking for both switches at logic level 1.
  
  Pauls example can certainly be adapted to do the above , I particularly like the way he has used IND , in case you have not checked it out yet take a look at INS , OUTS and DIRS under Memory and Variables in the PBasic help file these instructions allow you to read/write all or some of the16 I/O simultaneously
  
  Jeff T.