Trapping a flag/state change (rapidly)

[rmteo]

....but I need a whole heap of different pauses (& some quite longish...I've always had an epic fail when I've tried to use timers for long pauses!) ....now I realise I could just reset the timer preload value accordingly each time I need a different pause, but ....aaargh ....brainache. I guess that's what it comes down to... a solution that avoids brainache ...

Here is pseudocode that blinks 2 LEDs at different speeds (1Hz and 2Hz) and does not use any pause (blocking delay) type commands. You can easily expand it to any number of LEDs (or tasks) with no performance degradation. It uses a single hardware timer to provide a system tick (also known as a heartbeat). It can be used as a template to create simple multitasking applications.

sub timer1 interrupt
  inc(cyctick1)
  inc(cyctick2)

  if cyctick1 > 500      ' 500mS delay, 1st. counter
    cyctick1 = 0         ' reset counter
    cycflag1 = 1         ' set flag        
  endif
  if cyctick2 > 250      ' 250mS delay, 2nd. counter
    cyctick2 = 0         ' reset counter
    cycflag2 = 1         ' set flag 
  endif
end sub  

sub usrfunction1
  toggle LED0
end sub

sub usrfunction2
  toggle LED1
end sub

main:
  cyctick1=0:cyctick2=0 ' Initialize variables
  ccyflag1=0:cycflag2=0 '         "
  
  timer1 = 1000         ' set up timer1 to interrupt every 1mS

  while true
    if cycflag1=1 then  ' check if 500mS has expired
      cycflag1 = 0      ' reset flag 1
      do userfunction1
    endif
    if cycflag2=1 then  ' check if 250mS has expired
      cycflag2 = 0      ' reset flag 2
      do userfunction2
    endif
  wend