How to blink 8 LEDs at different rates- concurrently?

[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/

[rmteo]

No I have not seen that link, thanks for pointing it out. I looked at Salvo and several other co-operative and pre-emptive RTOSes. Salvo is actually quite nice and has a small footprint. However, at $1,500 for a full-source license, it is somewhat pricey for my current needs - although it must be said that compared to some other commercial (particularly the pre-emptive ones such Avix, CMX, etc.) products, you could still call it a bargain. There are several free (and/or open source) pre-emptive systems for higher end devices but I find them extremely cumbersome to use and very resource hungry. The few that I looked at required about 20K ROM and 5-6K RAM for a useable configuration. I am also wanting something that can be easily ported to other devices/platforms (such as PIC24/dsPIC33 and 32-bit ARM Cortex M0/M3) and can be implemented using only a high level language (whether BASIC or C).

I have implemented what is basically a time-sliced task handler that will do 16 tasks in about 250 bytes of ROM and 75 bytes of RAM - additional tasks require 2 bytes of RAM per task. Small enough to run on a PIC12/16 - reducing the number of tasks could reduce the ROM (and RAM) footprint even further. Works fine - as I mentioned in a previous post, I have an application where an RTC is implemented using one of the tasks as an accurate seconds counter.