On Sun, 2011-01-09 at 11:42 +0100, Javier Ros wrote:
> John,
> 
> I've been checking the integrators manual, and yes Encoder and Encoder_Sim
> HAL components are described, but references to the Canonical Encoder
> interface are done.
> 
> So I understand, they are different things:
> 
> a)Encoder at section 8.6 of the integrator manual is more like the
> description of a particular software implementation already present in HAL.
> 
> b)Canonical encoder (or canonical *) is more like what should be the
> elements that an EMC developer should expect/consider to exist in any EMC
> compatible encoder (*) interface, should it be a HAL software encoder (*) or
> the HAL interface to the real encoder (*) present in a for example
> MOTENC-100 card.
...snip

I'm not John, but from my study of encoder, it seems encoder is really a
software interface and decoder, or ABZ to numerical converter of
quadrature incremental encoder signals. It may be beneficial to move
towards this kind of terminology. Also I wonder if it might be better to
break the component into two separate components, interface and counter?

I tried to compose a canonical description (but didn't finish) by
compiling the information in;
Figure 8.8: Encoder Counter Block Diagram, in section 8.6 of the current
Integrators Manual,
http://www.linuxcnc.org/docs/EMC2_Integrator_Manual.pdf 

in connection with the encoder.9 entry in the html documentation,
http://www.linuxcnc.org/docview/html/man/man9/encoder.9.html 

then referencing various sample configuration files to see which pins
and parameters where essential and also commonly used.

The source code comes in handy too.
http://git.linuxcnc.org/gitweb?p=emc2.git;a=blob;f=src/hal/components/encoder.c;h=f20b7a68926f6582a482da7bcec404eb0d55015e;hb=HEAD
 
(Short URL) http://alturl.com/hrkus 

It seems the information and features relevant to Figure 8.8 has grown
over time, to about twice as complex as it is currently presented, but
few of the possible features are commonly used, so it may be better to
label Figure 8.8 as a basic presentation of a more complex component.
The text should cover or indicate the presence of all current features.
It creates confusion when information has to be sourced from various
locations and analyzed to get a comprehensive understanding, but on the
other hand, if I could figure out how encoder works using the present
information, most people should also be able to.
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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