How to share arrays among cogs

Dave Matthews · 2013-07-29 12:45

I have a 500 word array defined in my top object (controls), from which start another object (Test Object), passing the address of the data array to the second object which then runs a new cog. Is it possible to refer to the address of the array in the second object globally? In the example code of Test Object, the routine called 'second' will not compile, as expected. How can I do this without passing the Data1 variable from method to method throughout an object?

controls.spin Test Object.spin

Duane Degn · 2013-07-29 13:32

You either need to pass the address to "Second" or make the address a global variable within "TestObject".

To make the address passed to the Start method global define the variable in your VAR section.

VAR

  long dataPtr

And assign the value passed as a parameter to the variable.

PUB  Start(Data1, datastack)  : success       Stop
     dataPtr := Data1 
     success := (cog := cognew(Main, datastack) +1)

You then no longer need to pass "Data1" to the main menu since it can now use the global variable.

You can use "dataPtr" in your methods like this:

PUB Main | i  
  pst.Start (115_200)
        
  Repeat i from 0 to 25
   
    PST.newline
    PST.dec(i)
    PST.str(string (" : "))
     
    PST.hex(byte[dataPtr][i],2)   


  Second
   
PUB Second   | i


  Repeat i from 0 to 25


    PST.newline
    PST.dec(i)
    PST.str(string (" : "))
     
    PST.hex(byte[dataPtr][i],2)

Alternatively, you get by without the global variable if you pass the address received by "Main" to "Second".

PUB Main (Data1) | i  
     pst.Start (115_200)
        
   Repeat i from 0 to 25


       PST.newline
       PST.dec(i)
       PST.str(string (" : "))
    
       PST.hex(byte[Data1][i],2)   


  Second(Data1)
   
PUB Second(Data1)   | i

Of course the variable doesn't need to be named "Data1". The follow code would work the same way.

PUB Main (dataPtr) | i  
     pst.Start (115_200)
        
   Repeat i from 0 to 25


       PST.newline
       PST.dec(i)
       PST.str(string (" : "))
    
       PST.hex(byte[dataPtr][i],2)   


  Second(dataPtr)
   
PUB Second(localPtr)   | i
 ' use "localPtr" where "Data1" had been used in this method.

You can pass addresses back to the parent method by using the return value of a method. You could add a method just to pass the address.

For example, I often include the following method in my programs.

PUB GetFileName'' This method lets a parent object read the fileName
'' of this object.
'' With many projects, I like to be able to see
'' What code is currently loaded in the Propeller.


  result := @fileName

The buffer "fileName" is declared in a DAT section like this.

DAT fileName  byte "AS5055Spi130728a", 0

Of course you would have the buffer contain whatever data you like. The parent object could modify the buffer once it had the address.

Dave Matthews · 2013-07-29 13:56

Thanks, that works great (dataPtr). I will try some of the other suggestions later. I appreciate your time and help!

How to share arrays among cogs

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