MAC36NL - BACnet MS/TP client - Loss of communication with BACnet MS/TP server devices

Issue

The MAC36NL acts as a client device on the BACnet MS/TP network and, from time to time, loses communication with the BACnetMS/TP server device(s).

Possible causes and solutions

Different versions of baja and Niagara deamon

Differing versions of baja and Niagara deamon are installed on the controller.

It is caused by copying all JAR modules from the older version of Workbench to a newer one - usually, the intention is to move along all JAR modules downloaded from the Internet, e.g., iSMA_IO, iSMA_Graphics, or axCommunity, but after pasting the files the user checks the option to replace the files in the destination instead of ignoring the files.

Solution

To solve the problem, follow the below steps:

uninstall a target version of Workbench from the PC and make sure that the modules and sw folder have been removed;
reinstall the target version of Workbench on the PC along with installation files of the MAC36NL controller;
back up the station (preferably, with alarms and historical data) using the Station Copier tool in the controller’s platform;
perform cleanDist on the MAC36NL controller;
perform again the commissioning of the controller indicating the station to upload.

Wrong configuration of the RS485 bus

On the RS485 bus, there may be 2 (or there should not be any) termination resistors and maximum of one pair of biasing resistors. The MAC36NL controller is by default set to the BIA position for both ports, COM1 and COM2.

Solution

If more than one MAC36NL controller is connected to the RS485 network, only one of them can be set to the BIA position on the biasing switch. Please note that the END position also switches on the biasing resistors, so if there already is one MAC36NL controller set to END, there cannot be another controller set to the BIA position.

It is also advised to verify configuration of other manufacturers' controllers and make sure that there is only one controller on the bus which has pull-up resistors switched on and two controller at the ends of the bus with termination resistors switched on (or both extremes with terminators switched off).

Communication parameters not adjusted to devices on the bus

By default, after adding the MstpPort component, the serial port is set to a 9600 baud rate (the Baud Rate slot in the Link section) and to a 0 MAC address (the Mstp Address slot in the Link section). This configuration is a default Tridium configuration for all devices Powered by Niagara.

For iC devices such as I/O modules, panels, etc., the BACnet MS/TP default communication configuration is as follows:

baud rate 115200,
address set on a rotary switch.

Default settings in different devices may vary by manufacturer and it cannot be taken for granted that one or any of these parameters will be configurable.

If there is more than one MAC36NL controller on the bus, only one of them can be set to the 0 MAC address.

Solution

Verify the baud rate and MAC address settings in all devices on the RS485 bus, which the MAC36NL serial port is connected to. All devices must be set to identical baud rates but unique MAC addresses.

In case there are various manufacturers' devices on the bus, which differ by parameters' configuration options, resulting in no way to standardize all parameters between devices on the bus, it is required to divide the RS485 bus to two. To divide the RS485 bus, it is necessary to provide another RS485 port by exchanging MAC36NL to MAC36NL-RS.