delete lookahead fails

[gshort]

I am attempting to use buffer lookahead but need to change the CS to add or remove motors from it. I am following the example in the "Power PMAC Move Mode Trajectories 2011-01.pdf" manual on Page 65 which shows the following:

 

dwell 10 // Stop lookahead execution

cmd "&1 delete lookahead" // Delete buffer

cmd "&1 #4->100C" // Assign new motor to C. S. 1

cmd "&1 define lookahead 10000" // Redefine buffer

dwell 10

 

I've enhanced this to wait for the command to complete and check the return status:

 

open subprog disableLookahead

if (LOOKAHEAD_BUFFERSIZE != 0) {

Coord[PARTPROG_CS].LHDistance = 0;

dwell 10;

Ldata.CmdStatus=1;

cmd "&%d delete lookahead", PARTPROG_CS;

sendallcmds; while (Ldata.CmdStatus > 0) {dwell 0;}

if (Ldata.CmdStatus != 0) {

send 2 "disableLookahead: delete lookahead failed, Ldata.CmdStatus=%d\n", Ldata.CmdStatus;

}

dwell 10;

}

close

 

What I've found that this will from time-to-time fail with error 33 (buffer in use). When the failure occurs there has been a move before it but there has since been a dwell so I would have thought that the buffer was no longer in use.

 

When the failure occurred I tried "holding" the motion script with a while loop on a P variable. I then tried manually deleting the lookahead buffer from a terminal window and I continued to get the buffer-in-use error:

 

&1

delete lookahead;

stdin:4:17: error #33: BUFFER IN USE: delete lookahead;

delete lookahead;

stdin:5:17: error #33: BUFFER IN USE: delete lookahead;

delete lookahead;

stdin:6:17: error #33: BUFFER IN USE: delete lookahead;

delete lookahead;

stdin:7:17: error #33: BUFFER IN USE: delete lookahead;

delete lookahead;

stdin:8:17: error #33: BUFFER IN USE: delete lookahead;

 

Can you give me some ideas as to how to proceed with this ?

 

 

[bradp]

I am not in a place to test this but an idea is that perhaps the line Coord[PARTPROG_CS].LHDistance = 0 is causing the problem. Since it is getting set at calculation time you might need a dwell before this line so I would try this and see if it helps.

 

open subprog disableLookahead

if (LOOKAHEAD_BUFFERSIZE != 0) {

dwell10

Coord[PARTPROG_CS].LHDistance = 0;

dwell 10;

Ldata.CmdStatus=1;

cmd "&%d delete lookahead", PARTPROG_CS;

sendallcmds; while (Ldata.CmdStatus > 0) {dwell 0;}

if (Ldata.CmdStatus != 0) {

send 2 "disableLookahead: delete lookahead failed, Ldata.CmdStatus=%d\n", Ldata.CmdStatus;

}

dwell 10;

}

close

 

[gshort]

I just tried adding the extra dwell, but I'm afraid it didn't make any difference.

[bradp]

We have implemented a new feature to make changing from an axis to a spindle work without having to manipulate the lookahead buffer. In general it is not a good idea to manipulate the lookahead buffer while a program is executing because there are several potential pitfalls with timing that make it hard to handle correctly.

 

Here is how it works.

 

We have made three new axis definitions

 

&m#n->s motor is a spindle in CS m and uses the CS m feedpot

&m#n->s0 motor is a spindle in CS m and uses the CS 0 feedpot

&m#n->s1 motor is a spindle in CS m and always uses 100% feedpot

 

When the motor is defined as s it will respond to jog commands even though a program in that CS is executing. It will not respond to axis commands.

 

Changing from axis mode to spindle mode is as follows

 

dwell0 // must have something that stops LH buffer

Ldata.CmdStatus=1 // so know when cmd is executed

cmd"&1#2->s1" // change axis to spindel with fixed 100% feedpot

SendAllCmds // purge buffer

do

{

dwell0 // never have empty while() loop and want dwell0 executed at least once

}

while(Ldata.CmdStatus = 1) // could also check for an error

 

Changing from spindle mode to axis mode is as follows

 

dwell0 // must have something that stops LH buffer

Ldata.CmdStatus=1 // so know when cmd is executed

cmd"&1#2->y" // change axis to spindel

SendAllCmds // purge buffer

do

{

dwell0 // never have empty while() loop and want dwell0 executed at least once

}

while(Ldata.CmdStatus = 1) // could also check for an error

 

firmware dated June 9th 2011 or newer has this feature.