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Subject: Hardcoded scale factor on pmac
From: George Nicolas Kontogiorgos via Tech-talk <tech-talk@aps.anl.gov>
To: "giles.knap@diamond.ac.uk" <giles.knap@diamond.ac.uk>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Tue, 30 Jul 2019 12:51:10 +0000

Dear Giles,

 

Hope this e-mail finds you well.

 

I am working on a custom tripod system with its own kinematics. The hardware I am using is Power PMAC, as before with slits (Those e-mails about DMOV bug).

 

I had a problem in this project with scale factors. I am giving you my configuration to illustrate the problem:

 

  • Q89 = -24383899 (read on Power PMAC IDE)
  • MRES = 1 (This value was set to this in order to debug my problems)
  • SREV = 1

 

With this values I got 2147483648 with caget on my configured virtual motor. When I set MRES = 50e-6 mm/step (My encoder resolution) I got the correct value with caget instead of a factor 1e+4. So I started to search where is this factor and I found scale_=10000; on pmacCSAxis.cpp, line 24. Just for test, I changed this value to 1 and my caget get the correct answer.

 

Am I setting something wrong or there is a bug on this hardcoded scale_? Why there is a hardcoded scale factor? Note that  2147483648 is the saturated negative value for 2 complement with 32 bits because my Q89*1e4 is too big.

 

Best regards

George Nicolas Kontogiorgos

Electrical Engineer

Beamline Software Group (SOL)

Brazilian Synchrotron Light Laboratory (LNLS)

www.lnls.cnpem.br

 

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Replies:
Re: Hardcoded scale factor on pmac Wayne Lewis via Tech-talk

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