Inter-Process communication

ErNa · 2010-06-30 10:51

I like to present a method I now use for some time to synchronize processes, running in parallel on different cogs.

One of the reasons is, that calling a method may need a lot of parameters to pass and that is sometimes uncomfortable.

The idea behind that is: start a cog by loading a spin or asm method and have the method initialized, then running idle. Sending a command to the method triggers an action, which may be running ones or persistant.

Communication runs via a process control block, like PCB_IEnc for an incremental encoder.

CON   NmbIEncPar = 12      'Number of parameters, handed over to the incremental encoder process
Dat
PCB_IEnc  long   @IEncCmd, @IEncPos, @IEncOfs, @IEncRes, @IEncVTim, @IEncVCnt, @IEncTiSl, @IEncSens
               long   @IEncTiBa, @ScVal053, @ScVal054, @ScVal055

First I declare a constant NmbIEncPar, which is the number of parameters, passed to the process. Then, there is a table of NmbIEncPar pointers to the actual variables in global memories.

Then there is an enumeration of the process commands:

'CommandSet  of incremental encoder process
#1, Idle, Run, FreeRun, DetReso, LoadPar, Sweep

Now, as the main routine starts, the process has to be initialized:

IEncCmd  :=  NmbIEncPar     ' Tell the process how many pointers to initialize
i             :=  IEnc.start(@PCB_IEnc,@@0)-1   ' Start incremental encoder process
ifIEncRes  ==0
     ActState := CmdInvok (@IEncCmd, DetReso, i)  Returns if resolution of encoder detected, stays in 'FreeRun'
else
    ActState := CmdInvok (@IEncCmd, Run, 255)   'Run the incremental encoder in triggered mode (to be explained)

Now the incremental encoder is running and the position will be in IEncPos.
As a special feature: it may happen, that the resolution of the encoder is not fixed. If unknown at the start (hardware could be plugged in), then the default value of resolution is set to 0. If this is true, then the incremental encoder first has to pass the index signal twice running into the same direction, so resolution is known, stored to IEncRes and the programm run continues.
If the resolution is known, than the initial position is set to a value more than twice the resolution. When the encoder reaches index, the position is set to the correct value.

To be continued

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ErNa · 2010-06-30 19:54

There is now a little bit of rather cryptic code, but, it's worth to think a little bit about it.
This code is nearly independ from starting a Spin or an ASM process.

PUB Start( GlobPtr, AddrOffs) | i 

  Stop  ' Start can restart, therefore stop a possibly running cog first
  ' Create a local copy of the global pointer array and do the address correction "quick and dirty"
  repeat i from 0 to LONG[noparse][[/noparse]LONG[noparse][[/noparse]GlobPtr +   0]+AddrOffs]-1        ' The first parameter is the number of parameters
    LONG[noparse][[/noparse]@LoclPtr + (i<<2)] := LONG[noparse][[/noparse]GlobPtr + (i<<2)] + AddrOffs ' all pointers are 32 bit, the pointer address is byte oriented
      
  ifnot ID_cog
   [b] ID_cog := cognew(CogProc, @Sk) + 1[/b] ' starting spin
   [b] ID_cog := cognew(@ASM_Entry, 0) + 1[/b] 'starting ASM

  Result := ID_Cog 

PRI Stop
  if ID_cog
    cogstop(ID_cog~ - 1)

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ErNa · 2010-07-01 22:12

This is the main loop of an assembler process

DAT     org  0

ASM_Entry
        mov       Command,  #0                  ' Reset Command to zero
        wrlong    Command,  CommandPtr          ' Acknowledge: Process running

        mov       Command,  #5                  ' Number of implemented commands +1, to check range
        rdlong    DrGTimSli, DrGTiSlPtr         ' Get the time slice for speed measurement
        mov       DrGVelTim, cnt                ' Initialize start time
        jmp       #:Initial                                                  
:LoopCmd
        rdlong    Command,  CommandPtr          ' Poll for new command
:Initial
        cmp       Command,  #MaxCmd       wc    ' check for upper limit
if_nc   mov       Command,  #0                  ' if exceeded, replace by NOP
        add       Command,  #1            wz    ' Address one more in jump-table !
        add       Command,  #:JmpTab
        movs      :JmpTab,  Command
        nop                                      ' nop to allow emptying of pipeline
:JmpTab
        jmp       #0-0        ' Entry, now jump to jump to command
        jmp       #:LoopCmd ' 0: No command, continue polling       
        jmp       #:Idle    ' 1: Enter idle mode, here: stay in Idle mode        
        jmp       #:TrigRun ' 2: run incremental encoder in triggered mode      
        jmp       #:FreeRun ' 3: run incremental freely, without trigger      
        jmp       #:DetReso ' 4: determine resolution of incremental encoder
        jmp       #:LoadPar ' 5: reload parameters
        jmp       #:Sweep   ' 6: sweep in accordance with sweep-rate

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ErNa · 2010-07-02 09:39

kuroneko pointed me to this:

DAT     org  0

ASM_Entry
        mov       Command,  #0                  ' Reset Command to zero
        wrlong    Command,  CommandPtr          ' Acknowledge: Process running

        mov       Command,  #5                  ' Number of implemented commands +1, to check range
        rdlong    DrGTimSli, DrGTiSlPtr         ' Get the time slice for speed measurement
        mov       DrGVelTim, cnt                ' Initialize start time
        jmp       #:Initial                                                  
:LoopCmd
        rdlong    Command,  CommandPtr          ' Poll for new command
:Initial
        cmp       Command,  #MaxCmd       wc    ' check for upper limit
if_nc   mov       Command,  #0                  ' if exceeded, replace by NOP
[s]        add       Command,  #1            wz    ' Address one more in jump-table ![/s]
        add       Command,  #:JmpTab
      [b]  jmp      Command[/b]
 [s]       movs      :JmpTab,  Command
        nop                                      ' nop to allow emptying of pipeline[/s]
:JmpTab
[s]        jmp       #0-0        ' Entry, now jump to jump to command[/s]
        jmp       #:LoopCmd ' 0: No command, continue polling       
        jmp       #:Idle    ' 1: Enter idle mode, here: stay in Idle mode        
        jmp       #:TrigRun ' 2: run incremental encoder in triggered mode      
        jmp       #:FreeRun ' 3: run incremental freely, without trigger      
        jmp       #:DetReso ' 4: determine resolution of incremental encoder
        jmp       #:LoadPar ' 5: reload parameters
        jmp       #:Sweep   ' 6: sweep in accordance with sweep-rate

And I was so proud to have a piece of self modifying code!

Thank you for this hint. By the way: this asm module realizes an quadrature encoder with speed measurement. Will come in parts after I return from holidays

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ErNa · 2010-07-03 09:19

When the start method is called, all the pointers are stored to a data field starting at LoclPtr

LoclPtr  ' All the pointers to global memory, like defined in PCB_table
CommandPtr    long      0       ' Pointer to the command
DreGebPtr     long      0       ' Pointer to the global encoder value
DreGOfsPtr    long      0       ' Pointer to an offset to "adjust" encoder position
DrGeResPtr    long      0       ' Pointer to the number of increments per resolution
DrGVelTPtr    long      0       ' Pointer to a speed value (time between counts, slow speed)
DrGVelCPtr    long      0       ' Pointer to a speed value (increments per time, high speed)
DrGTiSlPtr    long      0       ' Pointer to duration of time slice for speed measurement
DrGSensPtr    long      0       ' Pointer to rotational direction

DrGTiBaPtr    long      0       ' Pointer to timebase value, if encoder is simulated
ScVal53Ptr    long      0       ' Test
ScVal54Ptr    long      0       ' Test
ScVal55Ptr    long      0       ' Test

more to follow

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RS_Jim · 2011-01-24 05:53

Hi ErNa,
This post came up on my recient post about memory so I thought I would give it a read. The problem I am having is that the snippets are confusing me. Is it possible you could post or PM me a file that shows the complete process from the top method thru to the assembly obj. I think I am seeing a pointer to a series of pointers that is being fed to the new cog.
RS_Jim

JonnyMac · 2011-01-24 12:45

I use the [unsigned] min and max operators to limit the command from hub before using a jump table.

getcmd                  rdlong  tmp1, cmdpntr                   ' check for command
                        min     tmp1, #0                        ' limit range
                        max     tmp1, #4                        ' commands + 1
                        add     tmp1, #jmptable                 ' prep for jump
                        jmp     tmp1                            ' do it
                       
jmptable                jmp     #cmdexit
do_cmd1                 jmp     #cmd1                       
do_cmd2                 jmp     #cmd2
do_cmd3                 jmp     #cmd3

cmdexit                 mov     tmp1, #0                        ' clear old command
                        wrlong  tmp1, cmdpntr
                        jmp     #getcmd

ErNa · 2016-02-07 12:45

This will be another entry to create method for making use of the pscpb

Inter-Process communication

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