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DylanB
Registered Member

Date Joined Feb 2006
Total Posts : 24

Posted 3/10/2006 12:38 AM (GMT -8)

Hi,

I have a simple routine for incrementing/decrementing a variable based on button states:

Get_Buttons:
  Btns = %1111                                  ' enable all four inputs
  FOR BtnIdx = 1 TO 5
    Btns = Btns & ~BtnBus                       ' test inputs
    PAUSE 5                                     ' delay between tests
  NEXT

  'check for a mode switch  (switch 0)
  IF Btns.BIT0 = 1 THEN
    motor_select = motor_select + 1 // 3      ' update motor_select    constrain  to 0-2
  ENDIF

'check for an increase in dt (switch 1)
  IF Btns.BIT1 = 1 THEN
   dt(motor_select) = dt(motor_select) + 1   'it would be nice to increment this by 10 sometimes...
  ENDIF

'check for a decrease in dt (switch 2)
  IF Btns.BIT2 = 1 THEN
   dt(motor_select) = dt(motor_select) - 1     'it would be nice to decrement this by 10 sometimes...
  ENDIF

'check for motor enable/disable  (switch 3)
  IF Btns.BIT3 = 1 THEN
    motorEnable(motor_select) = motorEnable(motor_select) + 1 //2      'constrain to 0-1
    'start the clock for this motor
    idx = motor_select
    GOSUB Set_Time
  ENDIF

RETURN

I would like to increment a value by 10 instead of 1 if a button state remains the same for a couple seconds... kind of like how many alarm clocks work.

Any tips on how i could do this ?

Thanks!

Dylan

Jon Williams
Registered Member

Date Joined Jul 2004
Total Posts : 6440

Posted 3/10/2006 6:51 AM (GMT -8)

If you're reading the the button(s) at a specific rate you can ad a counter that controls the increment rate. Let's say you're scanning the button every 100 ms and after 1 second you want to change the increment rate. You can do something like this:

rate1 = rate1 + 1 * btns.BIT1
IF (rate1 > 10) THEN
dt(motor_select) = dt(motor_select) + 10
ELSE
dt(motor_select) = dt(motor_select) + 1
ENDIF

Note that the first line of code will either add one to rate, or clear it based on the return value. You need to be a little careful with this as rate could roll-over from its max value to zero if the variable size is too small for the amount of time the button could be pressed.

Jon Williams
Applications Engineer, Parallax

Chris Savage (Parallax)
Forum Moderator

Date Joined Jul 2004
Total Posts : 10533

Posted 3/10/2006 7:47 AM (GMT -8)

You could also put a MAX 11 after the line to limit it from ever rolling over, and then you could use a NIB variable.

rate1 = rate1 + 1 * btns.BIT1 MAX 11

Chris Savage

Parallax Tech Support

csavage@parallax.com

Jon Williams
Registered Member

Date Joined Jul 2004
Total Posts : 6440

Posted 3/10/2006 1:08 PM (GMT -8)

Thanks, Chris, I don't often use the MAX operator and that's a perfect application.

Jon Williams
Applications Engineer, Parallax

DylanB
Registered Member

Date Joined Feb 2006
Total Posts : 24

Posted 3/14/2006 9:29 PM (GMT -8)

Thanks Joe and Chris for the great pointers. I was able to cobble together a solution like this:

'check for an increase in dt (switch 1)
  IF Btns.BIT1 = 1 THEN
   dt(motor_select) = dt(motor_select) + i
   i = i + 1   MAX 11        'constrain to NIB size
   IF(dt(motor_select) < 2 ) THEN
      dt(motor_select) = 2
      i = 1
   ENDIF
  ELSEIF Btns.BIT1 = 0 THEN
   i = 1
  ENDIF

'check for a decrease in dt (switch 2)
  IF Btns.BIT2 = 1 THEN
   dt(motor_select) = dt(motor_select) - d
   d = d + 1 MAX 11          'constrain to NIB size
   IF(dt(motor_select) < 2 ) THEN
     dt(motor_select) = 2
     d = 1
   ENDIF
  ELSEIF  Btns.BIT2 = 0 THEN
   d = 1
  ENDIF

note the hack used to prevent the dt variable from going below 2 ... would a MIN 2 fix this ... :

'wonder if this would prevent dt(motor_select) from going below 2
dt(motor_select) = dt(motor_select) - d MIN 2

Any ideas?

Thanks again,

Dylan

Jon Williams
Registered Member

Date Joined Jul 2004
Total Posts : 6440

Posted 3/15/2006 5:19 AM (GMT -8)

Using MIN in your hack will prevent dt(motor_select) from falling below 2, yes.

Jon Williams
Applications Engineer, Parallax

Tracy Allen
Registered Member

Date Joined Jul 2004
Total Posts : 2962

Posted 3/15/2006 9:04 AM (GMT -8)

You can replace this:

IF Btns.BIT1 = 1 THEN
   dt(motor_select) = dt(motor_select) + i
   i = i + 1   MAX 11        'constrain to NIB size
   IF(dt(motor_select) < 2 ) THEN
      dt(motor_select) = 2
      i = 1
   ENDIF
  ELSEIF Btns.BIT1 = 0 THEN
   i = 1
  ENDIF

with this

dt(motor_select) = dt(motor_select) + i MIN 2 MAX 300
i = (i + btns.bit1) * btns.bit1 MAX 11 MIN 1

Similarly for the second code block. That does not include setting i=1 when motor_select<2, I don't quite see what purpose that serves.

Tracy Allen
www.emesystems.com

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