do something once inside repeat

xanadu · 2012-03-04 11:57

I have this code using the LCD object and it's monitoring pin 1 of the prop. Having the LCD output in the monitor loop constantly refreshes the display. How would I make this only change the display if the pin input changes instead of refreshing each loop?

 repeat
   
   if ina[1] == 1 
     
     lcd.backlight(true)
     lcd.clrln(1)
     lcd.gotoxy(0, 1)
     lcd.str(string("Off"))     

   if ina[1] == 0 
     
     lcd.backlight(true)
      lcd.clrln(1)
      lcd.gotoxy(0, 1)
      lcd.str(string("On"))

Duane Degn · 2012-03-04 12:04

xanadu wrote: »

I have this code using the LCD object and it's monitoring pin 1 of the prop. Having the LCD output in the monitor loop constantly refreshes the display. How would I make this only change the display if the pin input changes instead of refreshing each loop?

You need to keep track of the previous state of the pin.

[COLOR=#ff0000]previousState := 2[/COLOR]  ' we want and invalid state to start with
  repeat
   
   if ina[1] == 1 and [COLOR=#ff0000]previousState == 0
[/COLOR]    
     lcd.backlight(true)
     lcd.clrln(1)
     lcd.gotoxy(0, 1)
     lcd.str(string("Off"))     
     [COLOR=#ff0000]previousState := 1
[/COLOR]     
   if ina[1] == 0 and [COLOR=#ff0000]previousState == 1

[/COLOR]    
     lcd.backlight(true)
      lcd.clrln(1)
      lcd.gotoxy(0, 1)
      lcd.str(string("On"))
      [COLOR=#ff0000]previousState := 0[/COLOR]

xanadu · 2012-03-04 12:17

Excellent, thank you.

Phil Pilgrim (PhiPi) · 2012-03-04 12:37

To add to Duane's comment, as a general rule, you do not want to make separate, non-independent sections of your code dependent on separate readings of a port. Although it's probably not critical in your code, such a practice can lead to a race condition. In your code, you could assign the value of ina[1] to a variable, say newState at the beginning of your repeat loop, then use newState in your if clauses. You can also use this to advantage to eliminate redundant code:

  previousState := 2  ' we want an invalid state to start with
  repeat
    if ((newState := ina[1]) <> previousState)
      lcd.backlight(true)
      lcd.clrln(1)
      lcd.gotoxy(0, 1)
      if (newState)
        lcd.str(string("Off"))     
      else
        lcd.str(string("On"))
      previousState := newState

-Phil

StefanL38 · 2012-03-04 12:53

@xanadu: OT but I have to post this: really great avatar! ROFLOL
best regards Stefan

xanadu · 2012-03-04 13:03

StefanL38 wrote: »

OT but I have to post this: really great avatar!
best regards Stefan

Thanks but the avatar was not my idea, a knock off version if you will hehe.

@PhiPi - Great input, I see I would need to do that for my code and will, thanks.

do something once inside repeat

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