How to blink 8 LEDs at different rates- concurrently?

[Darrel Taylor]

OUCH!

After running my loop in the SIM.
I realized the timing was Waaaayyyyy OFF.
Fortunately, the other examples were "OFF" too ... just not as far.

I've always said PAUSE is the worst statement in the BASIC language.
It got me again.

Here's a version that should compensate ...
It uses the CCP module in "Compare" mode to create a precise 10mS interval.
So when you give a delay value of 50, it actually takes 500mS, on the nose.

Sorry, it's more than 8 lines now.

DEFINE OSC 4
DEFINE BLINKYFREQ 100  ; 10mS periods

DATA 50,22,38,75,17,40,62,13  ; default periods for each Output
;----------------------------------------------------------------
CCPR1val  CON EXT      : @CCPR1val = (OSC*1000000/4)/ BLINKYFREQ
CCPR1     VAR WORD EXT : @CCPR1 = CCPR1L
Timer1    VAR WORD EXT : @Timer1 = TMR1L
CCPIF     VAR PIR1.2

LoopLED   VAR BYTE[8]
LoopCON   VAR BYTE[8]
x         VAR BYTE

;----[Initialize]------------------------------------------------
FOR x = 0 to 7         ; load the periods from EEPROM
    READ x, LoopCON(x)
NEXT X
;-- setup CCP1 and Start Timer1 --
CCPR1   = CCPR1val     ; set compare value
CCP1CON = %00001011    ; compare mode, special event 
Timer1  = 0            ; clear Timer1
T1CON.0 = 1            ; start Timer1

TRISB = 0              ; PORTB all OUTPUT

;----[Main Program Loop]----------------------------------------
Main: 
    x = (x + 1) // 8
    PORTB.0(x) = !(LoopLED(x) < LoopCON(x))
    LoopLED(x) = (LoopLED(x) + 1) // (LoopCON(x) << 1)
    IF x != 7 THEN Main
  Waiting: IF !CCPIF THEN Waiting
    CCPIF = 0
GOTO Main

Cheers,

[Mike, K8LH]

Darrel, that algorithm is slick!

Does PBP allow assignments in expressions like C? For example;

while(1)
{ x = (x+1)&7;
  portb ^= ((!(LoopLED[x]=(LoopLED[x]+1)%LoopCON[x])) << x);
  delay_us(2500);
}

[Darrel Taylor]

Thanks Mike.

Does PBP allow assignments in expressions like C? ...

Nope, not even a +=

However, your x = (x+1)&7 takes much less time than my x = (x + 1) // 8 (Modulus) approach.
What was I thinking?

Cool, thanks!

[keithdoxey]

Thanks Mike.

Nope, not even a +=

However, your x = (x+1)&7 takes much less time than my x = (x + 1) // 8 (Modulus) approach.
What was I thinking?

Cool, thanks!

DOH!!! The problem with working with so many different languages is that you can misread code. I took " //8 " to be a comment (Javascript style) that you were going to do it 8 times LOL

[sayzer]

If "8 lines" is about the loop part, then here is my code.


Think like a politician. Is is not less then 8?

<font color="#000080"><b>EEPROM </b></font><font color="#FF0000">0</font>,[<font color="#FF0000">50</font>,<font color="#FF0000">22</font>,<font color="#FF0000">38</font>,<font color="#FF0000">75</font>,<font color="#FF0000">17</font>,<font color="#FF0000">40</font>,<font color="#FF0000">62</font>,<font color="#FF0000">13</font>]
          <font color="#000080"><i>'RB0 - RB7 time intervals
    
</i></font>Time    <font color="#000080"><b>VAR BYTE</b></font>[<font color="#FF0000">8</font>]
Timer   <font color="#000080"><b>VAR BYTE</b></font>[<font color="#FF0000">8</font>]
Temp    <font color="#000080"><b>VAR BYTE
</b></font>Preload <font color="#000080"><b>VAR WORD
</b></font>T1CON = <font color="#FF0000">%00000000   </font><font color="#000080"><i>' 1:1 @4Mhz
</i></font>TMR1IF <font color="#000080"><b>VAR </b></font>PIR1.<font color="#FF0000">0   </font><font color="#000080"><i>' An alias for overflow bit.
</i></font>TMR1ON <font color="#000080"><b>VAR </b></font>T1CON.<font color="#FF0000">0


</font>Begin:
    Preload = <font color="#FF0000">55543 </font><font color="#000080"><i>'Timer1 preload value for excat 10ms. interval.
    </i><b>FOR </b></font>Temp = <font color="#FF0000">0 </font><font color="#000080"><b>TO </b></font><font color="#FF0000">7
        </font><font color="#000080"><b>READ </b></font>Temp ,Time[Temp]  <font color="#000080"><i>'Fill time-intervals.
        </i></font>Timer[Temp] = <font color="#FF0000">0        </font><font color="#000080"><i>'Clear timer array.
    </i><b>NEXT </b></font>Temp

T:
    TMR1IF = <font color="#FF0000">0
    </font>TMR1L = Preload.LowByte
    TMR1H = Preload.HighByte
    TMR1ON = <font color="#FF0000">1
    
</font>Start:

    <font color="#000080"><b>IF </b></font>TMR1IF <font color="#000080"><b>THEN </b></font>INT_TMR       ' 1 line. 

    <font color="#000080"><b>GOTO </b></font>Start
    

INT_TMR:
    TMR1ON = <font color="#FF0000">0
    </font><font color="#000080"><b>FOR </b></font>Temp = <font color="#FF0000">0 </font><font color="#000080"><b>TO </b></font><font color="#FF0000">7
        </font><font color="#000080"><b>IF </b></font>Timer[Temp] = Time[Temp] <font color="#000080"><b>THEN 
            </b></font>PORTB.<font color="#FF0000">0</font>[Temp] = PORTB.<font color="#FF0000">0</font>[Temp] ^<font color="#FF0000">1
            </font>Timer[Temp] = <font color="#FF0000">0
        </font><font color="#000080"><b>ENDIF
        </b></font>Timer[Temp] = Timer[Temp] + <font color="#FF0000">1
    </font><font color="#000080"><b>NEXT </b></font>Temp   
    
    <font color="#000080"><b>GOTO </b></font>T    

<font color="#000080"><b>END



</b></font>

[rmteo]

I am working on the skeleton of a generic task handler that will manage say 16 tasks concurrently. The LEDs are just simulating tasks that occur at set intervals. One of the tasks will be a seconds counter (with an interval of 1000mS) that is the basis of a RTC (good to the accuracy/stability of the HS crystal clock) and accurate timing is therefore an important concern. So using any kind of Pause or Delay function would not work.

Using a hardware timer is really the only way to do it. However, the timer also has to account for whatever time is used up by instruction cycles - which can vary depending on conditional branches and time spent in each task. DT's method of using a CCP in compare mode solves this problem nicely. Thanks.

[Bruce]

Have you seen this? http://www.microchipc.com/Hi-Tech_C_multitask/