Elapsed Timer Demo

[jmgelba]

This interrupt based timer runs in the background. Does that mean a pause in the main program will stop it or will it continue to run in the background? I am trying to de-bounce a switch.

[HenrikOlsson]

Hi,
A Pause (or any other command) will not interfere with the interrupt - it'll keep running in the background.
However, if you're interrupting at a high rate the context saving, interrupt code and context restore will take cycles from the main PBP program without it knowing so your pause may be a bit longer than what you specify. For non critical timings it's not a problem.

/Henrik.

EDIT: Obviosuly interrupting at ANY rate will take cycles away from the main program. What I mean is that the faster you interrupt the more cycles will "vanish" and any software timed routines like Pause, SERIN, Pulsin that you have in the main program will be affected.

[jmgelba]

No the pause length isnt critical. I'm trying to get one switch to start and stop the elapsed timer. So it needs a debounce and a wait period so that it doesnt immediately stop the timer again.

Here's what I have but it doesnt work to well:

loop1:

For A = 0 to 1000
     IF PORTB.7 = 1 and TimerRunning = 0 then 
     gosub StartTimer
   endif
next A

if SecondsChanged = 1 then
           LCDout $FE,2, dec2 Hours,":",dec2 Minutes,":",dec2 Seconds
           SecondsChanged = 0
        endif
        
For B = 0 to 1000
     If PORTB.7 = 1 and timerrunning = 1 then 
     gosub StopTimer
   endif
next B
goto loop1

This means the user has to press and hold the button for 1 second before the timer will start. However, if they press it for 1.5 seconds, then they only need to press it again for half a second and it stops. If they press it for 2.5 seconds, then timer has started, stopped and is half way to starting again.

I was wondering id something like this would work?

'If PORTB.7 = 1 then
'gosub StartTimer
'TimerRunning = 1
'pause 150
'endif

If SecondsChanged = 1 then
           LCDout $FE,2, dec2 Hours,":",dec2 Minutes,":",dec2 Seconds
           SecondsChanged = 0
        endif

If PORTB.7 = 1 AND TimerRunning = 1 then
'gosub StopTimer
'TimerRunning = 0
'pause 150
'endif

I think the problem with both of them is that there is no time between the on if then and the off if then, and there needs to be some sort of logic that says that if the timer is running and the button is still pressed, do not stop the timer until the button has been released and pressed again.

[Darrel Taylor]

It keeps running in the background.
The interrupts will not wait for PBP statements to finish.

Ok fine, ... for many years I've resisted making a count down elapsed timer for humanitarian reasons.
But if you guys are going to do it anyhow, I might as well make a new version of the Elapsed Timer.
I can only hope that if somebody uses it for nefarious purposes, they end up blowing themselves up.

Here's the test circuit.



Here's the test program ...

' Define LCD connections
DEFINE LCD_DREG PORTC   ' Set LCD Data port
DEFINE LCD_DBIT 4       ' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_RSREG PORTC  ' Set LCD Register Select port
DEFINE LCD_RSBIT 2      ' Set LCD Register Select bit
DEFINE LCD_EREG PORTC   ' Set LCD Enable port
DEFINE LCD_EBIT 3       ' Set LCD Enable bit
DEFINE LCD_BITS 4       ' Set LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 2      ' Set number of lines on LCD
DEFINE LCD_COMMANDUS 2000 'Command delay time in us
DEFINE LCD_DATAUS 50 'Data delay time in us

DEFINE  OSC 4

INCLUDE "Elapsed_DN.bas"  ; Elapsed Timer Routines

ZERO_LED   VAR PORTB.3

ANSEL = 0                 ' All Digital
ANSELH = 0
LOW ZERO_LED              ' start with LED OFF
OPTION_REG.7 = 0          ' enable PORTB pull-ups
PAUSE 250                 
LCDOUT $FE,1              ' Initialize LCD
PAUSE  250

Days = 1                  ' set initial time
Hours = 1
Minutes = 3
Seconds = 10

GOSUB StartTimer          ' Start the Elapsed Timer

Main:
CountDown = !PORTB.0
  IF SecondsChanged = 1 THEN  
     SecondsChanged = 0
     LCDOUT $FE,2, DEC Days,"d-",DEC2 Hours,":",DEC2 Minutes,":",DEC2 Seconds
  ENDIF
  IF ZERO_LED != ZERO THEN ZERO_LED = ZERO
GOTO Main

If the button on PORTB.0 is pressed it counts down.
If it is not pressed, it counts up.
The LED comes on when it reaches 0.

If you are using the countdown for a movie set, it has to stop at 1 second.
Put this in the main loop.

  IF (CountDown=1) AND (Days=0) AND (Hours=0) AND (Minutes=0) and (Seconds=1) _
      THEN GOSUB StopTimer

You'll need the ASM_INTS include from the original Elapsed Demo.

[jmgelba]

Question then. Can I place the LCDOUT routine in the interrupt so that the screen always updates, even if the main program needed to pause for a total length over 1 second? The reason is to keep the display updating correctly on the second, every second.

[Darrel Taylor]

NO!

You could in the Elapsed_INT version, but not in this standalone version.

[SteveB]

Darrell,
You should have put the stop at 1 sec in the code, and make people pull it out otherwise. Just a little step towards keeping the knuckle-heads from causing trouble.

[Darrel Taylor]

LOL Steve, I like that idea.

But as it is, they have to be holding the button down for it to count down.
If they're still holding it when it reaches 0 ... well ...

I know it can be bypassed, but don't tell them how

[jmgelba]

IF PORTA.2 = 1 OR PORTA.3 = 1 AND DIM = 1 AND timerrunning = 1 THEN
PORTA.0 = 1
ENDIF
IF PORTA.2 = 1 OR PORTA.3 = 1 AND DIM = 2 AND timerrunning = 1 THEN
PORTA.1 = 1
ENDIF
IF PORTA.2 = 1 OR PORTA.3 = 1 AND DIM = 3 AND timerrunning = 1 THEN
PORTA.0 = 1
PORTA.1 = 1
ENDIF

Looking for a more efficient way of doing this. I need to monitor 2 inputs and turn on the correct outputs only when the timer is running. This does compile but I havent tested it to see if it actually works. This snippet will go in the main loop of the program that runs while the timer counts down.

[HenrikOlsson]

Here's one idea

Temp VAR BYTE

If TimerRunning = 1 THEN
  If (PortA.2 = 1) OR (PortA.3 = 1) THEN
    Temp = PortA & %11111100
    PortA = Temp + DIM
  ENDIF
ENDIF

/Henrik.