In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Zoot wrote:

Yes, use an interrupt. Here is *pseudo* code. The important think is that really, all the ISR is doing is keeping time, both for delays in user interface work (buttons) and counting RCtime decays. I used 10us, but resolution is totally up to you. I'm not showing variable declarations or anything.

[code]
INTERRUPT 100_000 ' 10us "ticks"


Interrupt_Handler:
    
Update_RC_Time_But_Only_If_Flag_Set:

   IF doRCflag = 1 THEN
      IF rcPin = 1 THEN ' it did not fall to 0 yet (or rise to 1 depending on your circuit)
         INC rcTimer ' best as Word to get a decent amount of possible time
      ENDIF
   ELSE
      INC rcTimer ' to track charge time
   ENDIF

Update_User_Delay_Time_If_Flag_Set:

  IF doUserDelay = 1 THEN
     INC userTimer ' best as Word to get a decent amount of possible time
  ENDIF

   RETURNINT


Main_Program:
' the important think here is that the main loop keeps whipping through everything all the time
' and sets flags, pin states, clears counters, as needed...

Track_RCtime_Decay:

  IF doRCflag = 1 THEN ' are you in the middle of measurement?
     IF rcPin = 0 THEN ' pin finally fell, check and save the reading...
        doRCflag = 0
        rcValue = rcTimer
        rcTimer = 0
        HIGH rcPin  ' OUTPUT and high
     ENDIF
  ELSE  ' otherwise wait 2ms charge time (or whatever you want)
     IF rcTimer > 200 THEN '  2ms/10us
        INPUT rcPin  ' set to measure
        rcTimer = 0 ' clear the count
        doRCflag = 1 ' set the flag
     ENDIF
  ENDIF

  ' so at this point, you always have the most recent current reading from the RCTIME circuit in rcValue

Track_User_Button_Stuff:
   IF button0pin = 0 THEN ' active low
      IF userTimer > 50_000 THEN ' half second of "holding" button
         ' do something
      ELSEIF userTimer > 5000 THEN ' 50ms hold (so everything is debounced)
        ' do something else
       ENDIF
   ELSE ' released state, clear timer
      userTimer = 0 
   ENDIF


Do_Something:
  IF rcValue > 10_000 THEN
      ledPin0 = 1
  ELSE
      ledPn1 = 0
  ENDIF

Etc:

Done:

   GOTO Main

[/code]

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=438115#m438483

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2010 (http://www.dotNetBB.com)