A question about multiple pushbuttons

Comments

• Mike G Posts: 2,702

  2011-04-10 14:38 edited 2011-04-10 14:38

  I didn't test this... it depends how you have pins 13, 14, and 15 wired.
  

  ' {$STAMP BS2}
  ' {$PBASIC 2.5}
  
  Init:
    ' Set pin group A to input low
    DIRA = %0000
    OUTA = %0000
  
    'Set pin group D to output low
    DIRD = %1111
    OUTD = %0000
  
  Main:
  
    IF IN0 = 1 THEN  TOGGLE 13
    IF IN1 = 1 THEN  TOGGLE 14
    IF IN2 = 1 THEN  TOGGLE 15
  
  GOTO Main
  
• Brice Posts: 2

  2011-04-10 15:40 edited 2011-04-10 15:40

  Thank you for your reply. I tried the code you sent, something still seems to be wrong. I'm attaching a rough diagram of how I have it wired. Thanks again!

  

  

  IMG.jpg

  1024 x 1325 - 67K

  IMG.jpg 67K
• Tracy Allen Posts: 6,667

  2011-04-10 15:54 edited 2011-04-10 15:54

  When simple tasks have to be done in parallel, like you have here, multiple pushbuttons to multiple outputs, a state machine is a time-honored technique. The following program has 3 internal states stored in variables x0, x1 and xx. Variables x0 and x1 are simply the current and previous states of the input pins, and each bit corresponds to one of the pushbuttons. Variable xx detects changes that occur when any (or any combination) of those pushbuttons are pressed and then released. But you see, all that takes is the bitwise XOR and AND operators, "^" and "&" on the Stamp. Then another bitwise "^" is used to toggle the states of the corresponding output bits. All that in parallel within a loop that runs over and over quickly. It is possible now to add more instructions to the loop, which will slow it down some, but the logic of the state machine will continue to operate.
  
  

  x0 VAR nib
  x1 VAR nib
  xx VAR nib
  x0 = INA      ' initial state
  DIRD = %1110   '   pins p13, p14, p15 are outputs   
  DO
    x1 = INA     ' read the inputs
    xx = x0 ^ x1 & x1   ' look for transition 0->1 (release button to high state)
    x0 = x1      ' update the previous state variable
    OUTD = (OUTD ^ xx) << 1  ' toggle outputs, move up to p13..p15, p12 is low.
  LOOP
  
• Zoot Posts: 2,227

  2011-04-10 17:15 edited 2011-04-10 17:15

  A slight variation to Tracy's code that will "preserve" the output state of pin 12 so that other areas of the program may use it...
  

  x0 VAR nib
  x1 VAR nib
  xx VAR nib
  x0 = INA      ' initial state
  DO
    x1 = INA     ' read the inputs
    xx = x0 ^ x1 & x1   ' look for transition 0->1 (release button to high state)
    x0 = x1      ' update the previous state variable
    OUTD = (OUTD ^ xx) << 1  | OUTD.BIT0   ' toggle outputs, move up to p13..p15, keep p12 where it was
     TOGGLE 12 ' flash p12 rapidly regardless of what buttons are doing to leds
  
  
    ' remember if the pin assignments OUT = the pin assignments IN (in groups of 4) then you would not
  ' need the shift above (e.g., if the leds were on pins 12,13,14 and the buttons were on pins 0,1,2
  ' though you might still want to mask out pins not used by the LEDs so they are available to other
  ' parts of the program, e.g.
  '  OUTD = (OUTD ^ xx) & %0111  | OUTD.BIT3   ' toggle leds on p12,13,14 leaving p15 alone
  
  
  LOOP
  
• Tracy Allen Posts: 6,667

  2011-04-10 20:37 edited 2011-04-10 20:37

  Good point Zoot.
  
  Also I forgot to make the pins outputs using the command,
  DIRD = %1110
  but edited that into the program in my previous post. That leaves the pin p12 as an input.
• jc3III Posts: 21

  2011-04-14 09:23 edited 2011-04-14 09:23

  i know how to use the pushbutton, but I want to use the pc keyboard instead of the pushbutton. For example if I hit the "L" button then it will activate a pin. just like the pushbutton does.
• Zoot Posts: 2,227

  2011-04-14 09:29 edited 2011-04-14 09:29

  jjc3III -- use DEBUGIN. Also, you may want to start your own thread for your question.