Magnetic switch to mechanical counter

Comments

• Mike Green Posts: 22,925

  2019-10-03 - 17:00:04

  There are all sorts of simple examples in "What's a Microcontroller?" for testing switches and activating something (like a solid state relay) when the switch is opened or closed or whatever. How about making up a prose description of what you want your gadget to do? You could do a flowchart if you want, but that's more work to post. Once you have a description that you're happy with, it's easy to translate it to Basic.
• JonnyMac Posts: 6,375

  2019-10-03 - 17:12:09 edited 2019-10-03 - 23:16:14

  With XOR (^) you can determine which inputs changed, irrespective of how they changed. For example, let's say that IN0 and IN1 are normally open and IN2 and IN3 are normally closed. All inputs have pull-downs, and the other side of the switch connects to 5v.
  
  This bit of code samples the inputs and waits for a change. By using XOR we can find the pins that changed state -- a "1" bit in delta tells us the corresponding input changed. By looking at the actual value in the last scan, we can respond to that input as required.
  

  ' {$STAMP BS2}
  ' {$PBASIC 2.5}
  
  oldState        VAR     Nib
  newState        VAR     Nib
  delta           VAR     Nib
  
  
  Setup:
    DIRA = %0000                                  ' all inputs
    oldState = INA
  
  Main:
    PAUSE 25
    newState = INA
    IF newState = oldState THEN Main
  
  Change_Detected:
    delta = newState ^ oldState
    oldState = newState
  
  Process_Input0:
    IF delta.BIT0 = 1 THEN
      IF newState.BIT0 = 1 THEN                   ' normally-open input
        ' active
      ELSE
        ' released
      ENDIF
    ENDIF
  
  Process_Input1:
    IF delta.BIT1 = 1 THEN
      IF newState.BIT1 = 1 THEN                   ' normally-open input
        ' active
      ELSE
        ' released
      ENDIF
    ENDIF
  
  Process_Input2:
    IF delta.BIT2 = 1 THEN
      IF newState.BIT2 = 0 THEN                   ' normally-closed input
        ' active
      ELSE
        ' released
      ENDIF
    ENDIF
  
  Process_Input3:
    IF delta.BIT3 = 1 THEN
      IF newState.BIT3 = 0 THEN                   ' normally-closed input
        ' active
      ELSE
        ' released
      ENDIF
    ENDIF
  
  Clean_Up:
    GOTO Main
  

  Jon McPhalen
  Hollywood, CA
  It's Jon or JonnyMac -- please do not call me Jonny.