RE: Help with BiSS encoders and Galil controller

[Mark via Tech-talk <tech-talk at aps.anl.gov>]

Hi Jesse,
Reading the description of the issue, I'd also guess that the encoder 
and motor direction don't agree.
Also, I understand the definition of forward/reverse is being driven by 
the limits installation in this case.
Serial encoder scales include absolute position information and as such 
encode the direction too.  The Galil EPICS driver support for BISS 
doesn't support inverting/reversing the encoder scale. Inverting the 
scale is supported only for SSI encoders configured to use the binary 
data form and the motor must be open loop, since the invert happens at 
the driver layer.
It appears there could be two ways to move forward
1.  Physically reverse the encoder scale installation
2.  Alter the driver so that for open loop motors, the scale direction 
can be effectively inverted in software
The BISS medm screen indicators timeout, crc, warn and error are 
actually red when not active.  The colors are not a good choice, I'm sorry.
I'll review the Qt/MEDM screen colors in the future.  It appears no 
errors are occuring during the BISS-C read, from the information provided.
Given options 1, 2 above, option 1 is normally preferred because it 
works with closed loop motors and requires fewer calculations in the driver.
I'll reach out to you by email, in case option 2 above is required.
Kind regards,
Mark Clift

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