Mango and BACnet routers

I am trying to use Mango to monitor the temperature on an MS/TP device. I am using a BACnet/IP to MS/TP router. Mango can discover the MS/TP device and it shows me the current temperature but when I add it to my points it gives me an unknown object error. When I look at the Wireshark capture for the initial discovery and initial reading of the temperature I see the NPDU is correct and it contains the correct destination network number and destination address. However, when it begins to poll for the temperature it drops the destination network and destination address in the NPDU and the router replies with an unknown-object error as the request now targets the router instead of the thermostat.

Thanks,
Bennet

Are you sure all of the attributes for your point are completed? Can you post a screen shot of the point configuration (or an export).

I performed a BACnet discovery and selected the point from a list of points. I accepted the point details that appeared. This process worked when I polled a point from a BACnet/IP device which is on the same network as my computer. However, when there was a BACnet/IP to MS/TP router between my computer and the MS/TP device, this process did not work.

Here is an export of my Data Points. I don't see any routing information in here, for example the MS/TP network number or the MS/TP destination address. Do you send a Who-Is to get this information?
{
"dataPoints":[
{
"loggingType":"ON_CHANGE",
"intervalLoggingPeriodType":"MINUTES",
"intervalLoggingType":"INSTANT",
"purgeType":"YEARS",
"pointLocator":{
"dataType":"NUMERIC",
"objectType":"ANALOG_VALUE",
"propertyIdentifier":"PRESENT_VALUE",
"objectInstanceNumber":7,
"remoteDeviceInstanceNumber":76006,
"remoteDeviceIp":"10.0.0.213",
"remoteDevicePort":47808,
"settable":false,
"useCovSubscription":false,
"writePriority":16
},
"eventDetectors":[
],
"engineeringUnits":"",
"chartRenderer":null,
"dataSourceXid":"DS_463332",
"defaultCacheSize":1,
"discardExtremeValues":false,
"discardHighLimit":1.7976931348623157E308,
"discardLowLimit":-1.7976931348623157E308,
"enabled":true,
"intervalLoggingPeriod":15,
"name":"Room Temperature 1",
"purgePeriod":1,
"textRenderer":{
"type":"PLAIN",
"suffix":""
},
"tolerance":0.0,
"xid":"DP_644722"
}
]
}

Hi Bennet,

A bit confused. You initially said that discovery (at least) works with the MS/TP router. But now you're saying it only worked with IP?

The configuration looks ok. Can you provide the wireshark captures you mentioned in your first message?

I have seen no issues with BACnet/IP devices. I am having issues polling MS/TP points. If you look at the capture you can see it correctly request the temperature in line 117 but in line 258 it no longer includes the destination network number and the destination address in the NPDU. Line 258 is when it starts polling the temperature from the MS/TP device. Here you can see errors from every ReadProperty.

Matthew

Very coincidentally I came across this exact issue today. I have downloaded Bennet's capture and agree 100% with his description. I agree that when you use a RPM (Read Property Multiple) the request is coded correctly, but when you use a RP (Read Property) the request is missing the DADR and DNET in the NPDU part of the message, so the BACnet Router responds to the message with an unknown object error, because the Router does not know to pass the message on (oo DADR) so it tries to respond to the message as if it is addressed to itself, and of course it does not have such an object.

Just a note, if you can get this to work you will open up all BACnet sites that have MS/TP (RS485). Using BACnet IP to MS/TP routers are the traditional approach to automating sites. I guess more than 98% of sites are done this way.

I really encourage you to take a quick look at this issue. Since the coding seems fine in the RPM it can't be a big issue to implement it in the RP message.

Ed

What may not be evident from the capture is that ReadPropertyMultiples were used to discover the objects in my MS/TP device and to read the properties from these objects. Then when I selected one present-value to poll from one object in the MS/TP device, Mango used ReadProperties to get the present-value. As you said, the ReadPropertyMultiples had the correct routing NPDU where the ReadProperties did not.

The issue may be that the discovery process had the correct NPDU information and the polling process did not.

It may be that the discovery process uses the correct NPDU information, as this is discovered in the I-Am that is received during the discovery process. And when a discovered object is selected to be polled it may be that the NPDU is not stored for the polling operation. Or perhaps an initial Who-Is might be a better solution when polling begins in case the routing information for the object changes.

Gentlemen,

I seems that Mango is not maintaining the network information between the discovery in the data source configuration and the runtime operation. This should be an easy fix, but before providing a fix in a new release it would be good to have an opportunity to test it. Unfortunately we do not have the appropriate equipment here. Would one of you be willing to make an appropriate test bed available over the internet? If so, PM me with the details.

I could do this but this may require a special setup by you. Can Mango register as a foreign device with a BBMD? We have a BBMD and support foreign device registration (FDR). If not, can Mango act as a BBMD or do you have a BBMD at your facility? If you don't support FDR or have a local BBMD then you cannot send/receive broadcast messages over the Internet to our BACnet router. This will stop you from discovering devices on our network.

If you can enter the network information needed to communicate with our router and its MS/TP devices then you may not need to send broadcast messages over the Internet, using FDR or a BBMD.

Bennet

I would just be sending the network information, i.e. manually configuring Mango to be able to send the correct read multiple.

OK. I should be able to set this up by tomorrow evening.

Thanks Bennet. As discussed, this problem should be fixed in the next release.

Hi Matthew

Apologies for getting back to this issue so late. I can evaluate the fix but unfortunately not remotely. Are you able to send me something I can install at my site? If not, I can certainly validate the changes in the next release. When do you expect to release that?

Ed

Probably the next couple of weeks.