de Javu all over again.

When I wrote a day or so back about the NMRA process for standardising the very first part of their desired NMRAnet little did I know that a decision had already been made. Of course, the usual dictums of common courtesy seemed to have escaped the NMRA Board of Directors and the Standards and Compliance Manager. The working group was not informed. The authors of the document were not informed. The standard merely appeared at some point. The next line on the index page points to the as yet non-existent technical note.

At least in the version finally published some of the material so offended the Standards department manager was restored. But the sad part is that the changes which remain are just as offensive to the technical community. Even more amusing is that what we have asked for over so many months, something that supports the assertions of Don Voss, still hasn't been supplied, nor is it included either in the standard as published, or in the draft TN (the real one we dont know).

The standard suggests that we can adopt CAN bus yet vary it. I wonder if somebody, like Robert Bosch the inventors of CAN bus, has copyright control! The bastardised CAN bus we are presented with sinmply is not CAN bus. The Voss brothers ask that we accept that CAN bus certification of a component is required, but that an essential CAN bus specification, Rdiff(min), must be >20kohm. But Rdiff(min) is only tested to be >10kohm for CAN bus certification. A transceiver manufacturer may, but is not compelled to, state what Rdiff actually is, or the range that may be encountered.

All of this when they went to such lengths to try and justify this variation using data and application notes designed to sell specific products. By including a formula in the standard for determining the maximum theoretical under ideal conditions network length WHICH INCLUDES Rdiff AS A PARAMETER! Well, they sneakily dont say that, they include 20,000 as a constant. When in reality the maximum langth of the network, under those same conditions (or the maximum number of nodes) could be longer or larger if the original equation from NXP were used and the effective Rdiff left in place. Of course, after FOUR years of discussion it is hard to expect such rigour to be part of the standard isn't it?

Like I said, what did we really expect? Procedural fairness? Honesty and technical integrity? Openess of process and procedure? Well, this is the NMRA after all.