Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25204
Location: Livermore CA USA
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 Posted: Sun Feb 03, 2013 4:23 pm Post subject: (Case 117320) VP-200 Compatibility with Dynon Skyview 5.1 |
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(I sent the message below to Dynon this afternoon. FYI -Matt)
Dear Dynon Support,
I was forwarded the text immediately below regarding the new Skyview Version 5.1 issue and EMS data stream compatibility with Vertical Power VP-200
I think that Dynon is kind of missing the point here. Dynon has, for all intents and purposes, developed a "standard" for this EMS data format. Whether arbitrary 3rd parties use it and/or communicate that use to Dynon is also beside the point. Dynon has committed to a certain format and as such cannot change it without incurring some serious, potentially negative and/or life threatening ramifications in the field. The designers of TCP/IP didn't just randomly decide to change the order and meaning byte values in the standard. A standard is a standard. When its done and released, *its done*. Version 1.0 cannot be updated.
Adding a "version string" to the data stream doesn't work either as the devices listening to version 1.0 don't know the version string is there and are equally as broken.
The only option is to version each new format and allow the user to select between the various version. Or, depending on the flexibility of the protocol, ADD new data strings to the format. But the original data strings *cannot* be changed. For example, in NMEA0183, $GPGGAxxx, $GPRMCxxx etc. allow for a progression of new formats to be added. But the format of $GPGGAxxx always has to remain the same.
I work at a Government research laboratory in Livermore where I engineer and write embedded firmware for remote security terminals that are used throughout the Department of Energy sites. Part of that responsibility is to design, implement, and utilize serial protocols for communicating between various devices over both RS485 and Ethernet. If I were to make a change to our protocol like Dynon has done in the upgrade between 5.0 and 5.1, I would be fired. Plain and simple. Even IF everyone that is using the protocol happens to be notified of the change, there is still the issue of incrementally upgrading all of the end devices.
I guess my point here is that Dynon needs to take their various "proprietary" serial protocols a whole lot more seriously. I believe this is now at least the *third* time that a protocol change has adversely impacted the user community. That is *not* acceptable. I would have probably been fired after the first indiscretion, if not strongly reprimanded. The second and third times would just not have happened.
For protocol versioning control, Dynon needs to either add additional named strings to their protocol or they need to simply start versioning each change AND including support for all versions in their products. For example, the user should be able to select between EMS Version 1 or EMS Version 2 or EMS Version 3 from the configuration menu. The format of EMS Version 1 or any previous versions can never change; period.
And finally, given Dynon's lackadaisical attitude toward their protocol specifications, I find it almost impossible to believe that a simple downgrade from Version 5.1 to 5.0 is, by default, disallowed? Why aren't the same Draconian version control practices imposed on the customers, applied to their software developers as well?
Matt Dralle
RV-8/RV-6/RV-4
| Quote: | Forwarded Email (Originally from Dynon Support)
We updated the serial stream because we had some important customers that asked for specific elements to be added to the stream. We knew this was a possibility since day one, and even put a version number in the serial stream so an application can tell that the stream has been changed. We would always prefer to not change the format, but at some point you need to balance the needs of a variety of customers, and we had a clear business case to support customers asking for new features in the serial stream.
One of the issues here is that the VP-200 is not a product we "support." While we have official support for the VP-X,
Vertical Power used our serial stream for the VP-200 on their own accord without any input from us. This is fine and in fact the whole reason that we created a documented serial stream, but this means we didn't even really know they were using it so it's hard for us to realize that we were going to break anything. Compatibility is something that we test every release for products we support, but isn't something that we can promise for arbitrary 3rd party devices that few of our customers use.
We only moved a few parameters around in the new serial stream, so it's unfortunate that it will take them months to fix this as it's likely just a few constants in their code to make it work again.
It is possible to revert to 5.0 without much hassle. Contact support via email or phone and we can send you instructions.
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At 03:48 PM 2/1/2013 Friday, Dynon Technical Support wrote:
[quote]Matt:
Another customer told us today that Vertical Power recommended not updating to v5.1 because of changes Dynon made to the streaming data format.
We advise talking to Vertical Power first.
Thanks,
Steve
Dynon Avionics Technical Support
support(at)dynonavionics.com
Phone: 425-402-0433 - 07:00-17:00 Pacific weekdays
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