Passing Variables in and out of new cog

steprog

Hi Guys,
Simple question, but I can't seem to find a simple answer. If you call a new cog to run a method and it generates new data that the first cog needs how do you pass it back to that cog. I know how to do it when the new cog runs an assembly routine, but not when it is a simple spin program. This should be real simple, but for some reason I'm not getting it.
Help

Thanks,
Greg

jbalat

I would just declare it as a global variable that way you dont have to pass it...

You dont want to get into a situation where you are trying to write to it with 2 cogs. If so you would need to use the lock commands..

StefanL38

easiest way in SPIN is to define PUB methods GetVar

VAR
  long MyVar

PUB GetMyVar 
  result := MyVar

Let's say your object that contains PUB GetMyVar is named MySecondObject


in your first *.SPIN-file you define

OBJ 
  MyObj2 : "MySecondObject"

VAR
  long MyVarINSpin1

PUB YourCodeInSPIN1
  '...

  MyVarINSpin1 := MyObj2.GetMyVar

best regards

Stefan

steprog

Thanks guys, I knew this had to be simple.
Greg

Phil Pilgrim (PhiPi)

steprog,

Just to summarize, so you understand the difference between the two answers you got: jbalat's answer is correct when both Spin cogs are part of the same object. If they're not, then StefanL38's "accessor function" method is the one to use.

Cogs and objects are different entities altogether, and it's important to grok the difference between them when programming.

-Phil

steprog

I'm still trying to get my head around Stefan's explanation. I called parallax and they claim that if it is declared globally then I can use it just like any other global variable. I am calling another method in a new cog however. But a global variable is a global variable so I thought.
Greg

kuroneko

steprog wrote: »

I called parallax and they claim that if it is declared globally then I can use it just like any other global variable. I am calling another method in a new cog however. But a global variable is a global variable so I thought.

Running a method in a new cog means the method is located in the current SPIN file (doesn't work any other way). So let the method access the global variable.

VAR
  long  a, b, stack[16]
  
PUB null

  cognew(secondary, @stack[0])
  repeat
    a := b

PRI secondary

  repeat
    b++

DAT

The only way this doesn't work is when the method is hidden in another object. Then it simply can't see the global variable defined in it's parent file but you could still pass an address reference which would allow the method to access it (e.g. long[address] := value).

Maybe you could tell us where your 2nd method is located (same or different object)?

steprog

Right now I'm having another problem with simply getting a cog to start. It might be related, so let me hold off until I work that out.
Thanks,
Greg