Hello, I need to know if can I have multitasking with one SX28 ACDP microcontro

markuster · 2007-06-19 01:35

Hello,

·I need to know if can I have multitasking
with one SX28 AC/DP microcontroller.

Do you know information about that ?

Thanks, Mark

Bean · 2007-06-19 02:05

What type of multitasking ?
What operations do you want to multitask ?

Bean.

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·

markuster · 2007-06-19 02:28

Thanks:

I want to use the basic compiler to move
two servos and a little piezo and a pair of
light sensors.

Do you know if SX are better for multitasking
than Basic Stamps.

Thanks, Mark

JonnyMac · 2007-06-19 02:48

I've attached a framework program that will show you one way to do it -- note that this is a simple program so the Interrupt Service Routine is coded in SX/B.

markuster · 2007-06-19 18:43

Thanks,

Do you know if can I "join" two or more SX28
in order to have something like the propeller,
something with real multitasking?

thanks, Mark

Bean · 2007-06-19 18:49

You could but you would be better off just using a propeller.

Bean.

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·

markuster · 2007-06-20 01:51

Thanks Bean:

But the problem I have is that the SX chips have
the Basic compiler (very similar to Basic Stamps)
and the Propeller doesn't have basic compiller . Propeller
uses a Spin lenguaje and it is different to Basic.

Do you know if there are or if Parallax will develop
somethig like to Basic for the Propeller ?

Thanks, Mark

PJMonty · 2007-06-20 01:57

Mark,

Why do you want "real" multitasking. If "standard" multitasking (simulating multiple processors through some form of time sharing) accomplishes your goal, AND you already have the SX chips and IDE, then just use it. There are millions of computers out there multitasking away (almost every PC and Mac for example) and accomplishing lots of useful goals. If you don't know how to multitask with a single processor, then it sounds like there are still things for you to learn about the SX. I would stick with what you know until it no longer can do what you want.

Thanks,
PeterM

Bean · 2007-06-20 12:20

markuster said...
Thanks:

I want to use the basic compiler to move
two servos and a little piezo and a pair of
light sensors.

Do you know if SX are better for multitasking
than Basic Stamps.

Thanks, Mark

Mark,
· I don't think you would need multitasking to to what you want.
· Just have your main loop do each thing one after the other.
· The servos should only be updated every 20mSec or so anyway.

Bean.

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·

LoopyByteloose · 2007-06-20 14:18

The 2004/5 SX Design Contest has a multitasking system as one of the honorable mentions.· Of course, this is assembly language - not SXB.· But any really good multitasking will probably be in assembly language in order to be compact and fast.

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Zoot · 2007-06-20 19:43

Mark, I concur with Bean -- if your initial goal is to run the piezo, a few light sensors, and some servos, keep it simple until you need it more complex.

You can develop a program that will "appear" to run everything at the same time ("multitask") since the SX is very fast, and 20ms between servo pulses is a lot of time to get other things done.

Here is a pseudo-code outline that may help:


Beginning:

    ServoTime = 0?   'if you countdown your servo timer to 0, send a pulse
          Yes --> send servo pulse(s) to servo pins
                --> reset ServoTime to equiv. of 20ms to countdown to next pulse
           No --> ServoTime = ServoTime - 1
     LightTime = 0?  'similar to above, but it's how long between light sensor measurements...maybe 10x per second (100ms)?
           Yes --> get light values into LightValL, LightValR, etc..
                --> reset LightTime to evuiv. of 100ms
            No --> LightTime = LightTime - 1

      PiezoTime = 0? 'ditto -- how often should script check for something to send to piezo -- this could be trickier without an ISR
                             'as you might need to break your sounds into small chunks that fit between 20ms servo pulses
              Yes --> make a sound, reset PiezoTime
              No --> PiezoTime = PiezoTime - 1

 Middle:
       
        LightL > 200   'is light on the left? turn that way
            Yes --> ServoL = 140, ServoR = 160
        LightR > 200   'is light on the right? turn that way?
             Etc.            'turn right


 End:
      GOTO Beginning

So basically your SX rips through the loop at blazing speed, but what actually happens during each loop depends on the state of the timer(s) -- the actual "send to servo" code will only run when 20ms has elapsed, etc. The above is over-simplified, but hopefully it gives the general idea of how you might approach the project. My own style is usually to use just a few counters, updated regularly, and then divide them for my different "tasks", but the individual timers above are easier to read.

JonnyMac's ISR routines, and PJV's multi-tasking threads give much tighter timing control and lets you run code virtually in the "background", which could be helpful for your sound work. But understanding the basics of something like the above would help. I've done similar setups on Stamps as well, though they are much slower overall.

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Hello, I need to know if can I have multitasking with one SX28 ACDP microcontro

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