Subject:
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Re: 3T
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Newsgroups:
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lugnet.org.us.laflrc
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Date:
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Fri, 3 Mar 2006 19:13:10 GMT
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Viewed:
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1781 times
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In lugnet.org.us.laflrc, John Brost wrote:
> program 3T{
> // lots of variables declared
> event scancomplete when scandone = 1
> main {
> scandone = 0
> start scan
> wait until scancomplete
> stop scan
> }
> task Scan {
>
> if A = 0 {
> //move to A location and scan for block
> CurX = 1
> CurY = 1
>
> <code here to scan and set A to 1 if block is present>
>
> if A = 1 {
> // if block was present A is 1 now
> // return scanner to home position
> CurX = 0 // set variable CurX to 0-- home position of scanner
> CurY = 0 // set variable CurY to 0-- home position of scanner
> set scandone = 1 // scandone variable is watched by an event
> // when event fires scan task stops
> }
> }
> If B = 0 {
> //repeat same steps for B location
> }
> }
Actually, John, I think I may be able to explain the problem. You have two
tasks running at the same time. For the most part, the processor will switch
between the main task, and the scan tast. So, the order of execution would be
something like this with the main (M:) and scan (S:) tasks
...
S: if A=1
M: check for event scandone =1 (not 1, so false)
S: CurX = 0
M: wait until scancomplete (no event; false)
S: CurY = 0
M: check for event scandone =1 (not 1, so false)
S: scandone = 1
M: wait until scancomplete (no event; false)
S: (brackes don't count as lines) if B=0
M: check for event scandone =1 (true)
S: CurX = 1
M: wait until scancomplete (event = true)
S: CurY = 2
M: Stop scan
S: May execute next line or stop
Does that make sense? This sort of timing problem is very common with threaded
applications.
Again, my suggestion is to add: "if scandone=1" the line before every "if b=0"
Steve
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Message has 1 Reply:
 | | Re: 3T
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| In lugnet.org.us.laflrc, Steve Hassenplug wrote: <snip> (...) Ok, that makes some sense, thank you very much. I hate the thought of nesting that many more if statements, but that does appear to be the best way to solve the problem. Thanks John (19 years ago, 3-Mar-06, to lugnet.org.us.laflrc)
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Message is in Reply To:
| | 3T
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| Well, I've had some time on my hands, and being totally unhappy with my 3T robot I decided a re-build was in order. Probably an 85% - 90% rebuild. About the only thing that wasn't touched was my cube magazine & the dropper mechanism. Everything else (...) (19 years ago, 3-Mar-06, to lugnet.org.us.laflrc)
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