Hi @jurjenhoekstra, @Greg Ireland and @jonnys, thank you for all your questions and input.
@Jeroen and myself have been on the phone the last couple of hours spelling out all the nitty gritty details regarding the NMEA2000-out function in the GX Devices. As well as writing down in as clear and complete a manner as possible all there is to know about instances.
Can I ask you to close read & review? I hope it helps to solve your issue. If you have any comments, please comment to this answer. Thank you! Matthijs
@Greg Ireland, hi Greg. Looked at your facebook page, great adventures. In case your are interested, I keep a weblog of the build of my yacht: Xanthiona. It has a lot of technical stuff, not so many adventures yet.
I did a search on the Victron Community on 'multiple bmv' and found there are some issues when trying to connect 2 BMVs to a Victron system. I believe it contributes to your issue of trying to get the information of both BMVs on the N2K View. Take a look at some of those issues, it might help or point you to the right direction.
To me it also would seem most logical to change the device instance and you would expect once that is done, that N2KView would be able to handle that. You could try changing the system instance, what we discussed yesterday.
On the other hand, it is the Venus GX who has to put the information from both BMVs onto the N2K network and as long that is done the same way for both BMVs without distinction between the 2, N2K will see them as one.
I think you might need some assistance here from a Victron staff member.
@mvader (Victron Energy), hi Matthijs, can you assist in this issue?
@jurjenhoekstra Good idea Jurjen, my vessel has 4 batteries, one for each engine, house bank and a back up navigation battery. I have previously been monitoring them via a Blue Power Panel and 4 shunts, however with the install of a Venux GX I was keen to get the battery data onto my Maretron N2K system.
I installed a 712 and connected my House Bank via a shunt and the Port Start Batt to the 2nd input to test, waited patiently for 12 months for the Venus Firmware to work and successfully displayed both batteries on N2K View. N2K View is configured to display battery instances 0 and 1.
Having had success, I installed a second 712 to monitor the Navigation Bank via a shunt and the Starboard Start battery on the 2nd input. But both are reporting on the same Device Instance, I would expect that I should be able to change it to Device Instance 1 (as it is the 2nd 712 on the system) and be able to change battery instance to 2 and 3 thus allowing me to separate them on N2K View.
As for the Tanks all report perfectly on N2K view, but it would be great to separate them on VRM for remote monitoring capability as I don’t use Maretron as it is silly expensive.
Thanks for your help, I really appreciate it - if you are interested you can see a bit more about my vessel at https://www.facebook.com/TSMVSeachange/
@Greg Ireland, hi Greg. Let's take a step back to your original question as to better understand what your are trying to solve: why are you trying to change the data instance for the BMV712? What is the exact problem? Is one of the BMV's not showing up on VRM or are you getting no data? This 6 + 2 = 50 does not make any sense to me.
By the way the setup on your yacht is quite similar to mine: Quattro 24-8000, Venus GX, Simrads and some Maretron stuff. Separate answer on the tank issue.
@jurjenhoekstra Hi Jurjen, thank you for your input, I am still unsure how the unique instance adds up to the upper and lower limits ie 6 + 2 = 50? The image below shows the Device Instance column added and showing 50 but the battery instances still at 0 and 1. The instance 50 does not register any data on my display.
Also, I have added an image for the tanks/pressure sensors, as you will see they are all Device Instance 0 but Tank Instance 0, 1, 2, 5 respectively.
There should be no need to change data instances on the CAN-bus. From the specs: "Data instances shall be unique in the same PGNs transmitted by a device. Data instances shall not be
globally unique on the network. Field programmability shall be implemented through the use of
PGN 126208, Write Fields Group Function."
Preferably, don't change them. It is a workaround for broken implementation. If the Yacht Devices Can Log Viewer can change them depends if mentioned write fields is implemented, which I doubt. The Maretron doesn't support it as far as I know. But the best solution is to just fix setups which incorrectly assume network wide unique data instances.
I am also having difficulties with this, I have two BMV-712 devices and despite modifying the instance number via Maretron N2K Analyzer the instance within the devices remain at 0.
Are we able to directly change the device instance number?
See images showing PGN's being transmitted.
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