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-   -   LabVIEW Encoder not reliably returning Rate (http://www.chiefdelphi.com/forums/showthread.php?t=89257)

billbo911 04-02-2011 12:22
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by Tom Bottiglieri (Post 1015138)
So, was there ever a fix for this?
There was a new LV Update released a couple days ago. LV Update 3.1 for 2011.

Does anyone know if this issue was resolved with that update?

kamocat 04-02-2011 12:23
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by Doug Norman (Post 1008167)
I have reproduced this and believe it is a bug in our code. I suspect we may document this rather than fix it for this season for two reasons:
1. It would be a risky fix.
2. There is the work around of writing your own rate code.
Do you have a single document describing all the bugs this season?

EDIT:
The Readme describes some of them, but leaves out CAN issues.
Is there a document that shows new issues, BEFORE a fix is created?

Greg McKaskle 04-02-2011 12:51
Re: LabVIEW Encoder not reliably returning Rate
 
I do not believe this release has a fix for this bug. I saw a post from Joe stating who would not let him fix it. He also didn't indicate whether he had really really fixed it this time, sorta fixed it, turned it into a feature, or other.

I agree there should be a known issues list along with workarounds. I'm not sure if the support forum has one. That would be the appropriate place to request one.

Greg McKaskle

billbo911 04-02-2011 13:58
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by Greg McKaskle (Post 1015549)
I do not believe this release has a fix for this bug. I saw a post from Joe stating who would not let him fix it. He also didn't indicate whether he had really really fixed it this time, sorta fixed it, turned it into a feature, or other.

I agree there should be a known issues list along with workarounds. I'm not sure if the support forum has one. That would be the appropriate place to request one.

Greg McKaskle
It has NOT been fixed in this update!

From the 3.1 README:

Quote:
Known Issues:
When you use more than one encoder, the rate indicator does not update for all encoders. To avoid this behavior, write your own encoder rate code.

Joe Ross 04-02-2011 14:02
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by billbo911 (Post 1015527)
There was a new LV Update released a couple days ago. LV Update 3.1 for 2011.

Does anyone know if this issue was resolved with that update?
The readme for LV Update 3.1 (included in the zip file) lists the encoder rate issue as a known issue and suggests that you write your own rate code.

Tom Bottiglieri 04-02-2011 14:03
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Known Issues:
When you use more than one encoder, the rate indicator does not update for all encoders. To avoid this behavior, write your own encoder rate code.
Or,
"You're holding it wrong."

jhersh 04-02-2011 14:06
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by Tom Bottiglieri (Post 1015524)
Can we create these on an unused DIO slot? Unused IO pins on the one DSC we have are hard to come by.
Yes... they can on slot 6.

apalrd 04-02-2011 15:25
Re: LabVIEW Encoder not reliably returning Rate
 
Is there any reason why it worked fine last year (cRio image 20) but doesn't work this year (tested cRio image 25)?

Also - Will it care if I allocate the dummy encoders on slot 6, if I don't actually have a DIO module on slot 6?

Also again - Is it that every other encoder works, or every other encoder created works? If I were to edit the VI that assigns counters (or encoders), and told it to only assign the odd or even counters (or encoders), would that fix things?

billbo911 04-02-2011 15:29
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by apalrd (Post 1015637)
Is there any reason why it worked fine last year (cRio image 20) but doesn't work this year (tested cRio image 25)?

Also - Will it care if I allocate the dummy encoders on slot 6, if I don't actually have a DIO module on slot 6?

Also again - Is it that every other encoder works, or every other encoder created works? If I were to edit the VI that assigns counters (or encoders), and told it to only assign the odd or even counters (or encoders), would that fix things?
What would be really nice is if we were told exactly what the "bug" was so that we could fix it.
I know that we can create our own code, but knowing what is wrong with the current one could help us NOT create our own buggy code.

jhersh 04-02-2011 15:52
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by apalrd (Post 1015637)
Is there any reason why it worked fine last year (cRio image 20) but doesn't work this year (tested cRio image 25)?
Because the FPGA image is different than last year.

Quote:
Originally Posted by apalrd (Post 1015637)
Also - Will it care if I allocate the dummy encoders on slot 6, if I don't actually have a DIO module on slot 6?
No... it won't care. And neither will you because you aren't using them.

Quote:
Originally Posted by apalrd (Post 1015637)
Also again - Is it that every other encoder works, or every other encoder created works? If I were to edit the VI that assigns counters (or encoders), and told it to only assign the odd or even counters (or encoders), would that fix things?
Based on reports, it is every other encoder... so if you change the VI to assign only even encoders, then they should all work. I have not actually tried this approach so I can't guarantee that it will work, but it sounds reasonable.

Alan Anderson 04-02-2011 15:52
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by billbo911 (Post 1015641)
What would be really nice is if we were told exactly what the "bug" was so that we could fix it.
We can't touch the FPGA code. It's going to stay broke.

jhersh 04-02-2011 15:55
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by billbo911 (Post 1015641)
What would be really nice is if we were told exactly what the "bug" was so that we could fix it.
I know that we can create our own code, but knowing what is wrong with the current one could help us NOT create our own buggy code.
The actual bug is most likely in the FPGA (we believe... we haven't actually debugged to find what the bug is exactly) and therefore not implemented the same way you would implement it in your code. Therefore there should be little risk of you writing code with the same problem.

-Joe

cabbagekid2 05-02-2011 01:53
Re: LabVIEW Encoder not reliably returning Rate
 
No one postd anything about having a lot of noise from the encodes so I figure I should ask again.....how does the signal from the encoders look? Ours looks extremely ugly. To the point where when we apply a median filer what we get out is almost half of the peak rpm being measured.

Joe Ross 05-02-2011 11:18
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by cabbagekid2 (Post 1015982)
No one postd anything about having a lot of noise from the encodes so I figure I should ask again.....how does the signal from the encoders look? Ours looks extremely ugly. To the point where when we apply a median filer what we get out is almost half of the peak rpm being measured.
You can reduce the noise by using 1x decoding rather then 2x or 4x. This eliminates noise introduced by the phase error of the encoder.

rwood359 06-02-2011 16:29
Re: LabVIEW Encoder not reliably returning Rate
 
Quote:
Originally Posted by jhersh (Post 1015652)
Based on reports, it is every other encoder... so if you change the VI to assign only even encoders, then they should all work. I have not actually tried this approach so I can't guarantee that it will work, but it sounds reasonable.
Even starting with zero or one?
Is the procedure to start with a dummy and then daisy-chain error out and error in to create the sequence?


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