do something once inside repeat

Comments

• Duane Degn Posts: 10,588

  2012-03-04 12:04 edited 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 Posts: 3,347

  2012-03-04 12:17 edited 2012-03-04 12:17

  Excellent, thank you.
• Phil Pilgrim (PhiPi) Posts: 23,514

  2012-03-04 12:37 edited 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 Posts: 2,292

  2012-03-04 12:53 edited 2012-03-04 12:53

  @xanadu: OT but I have to post this: really great avatar! ROFLOL
  best regards Stefan
• xanadu Posts: 3,347

  2012-03-04 13:03 edited 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.