Mbus Driver Guide

Discovery Guidelines

The 'Device' discovery process consists of firstly locating the devices and then for any that respond, enquiring from them information about their available data. This data is then cached before adding to an internal database and finally presented as discovered devices at the appropiate area of the driver.

Device Discovery

Introduction

In a similar manner to other Niagara AX drivers the wizard can be accessed from the network's device manager view. Clicking on the Discover button will show the Discovery Wizard, which presents the various discovery options for locating devices.
As devices can operate at different communications baud rates you can select the baud rates to scan against.
If devices take a long time to respond during the scan, you can continue to the later steps in the wizard and customise the timings for these slower devices.

The discovery wizard flow of options is:

1. Selection of discovery type
2. If supported by the connection (serial only) the individual baud rates to run multiple discoveries.
3. Options specific to the discovery type selected. E.g. A primary address discovery will have a range to scan
4. Optional setup of specific timings to compensate for slower devices.

The only option to bypass step 2 is when the driver is retrieving data from the locally cached data in the database.

Discovery types

DiscoveryWizard-ModeSelection




Primary Address Search Discover

This discovery procedure will proceed at the requested baud rate, checking if a device is addressable at a given primary address. The valid range is between 0 - 250.
Every address in the range to be checked requires messages, and therefore the range should be kept as small as possible to minimize the wait while each address is checked.
The range is scanned at every selected baud rate, therefore selecting only those baud rates you expect devices to be operating on will save time.. A scan is done for each baud rate in speed descending order. Where a device is found operating at a higher baud rate the address will not be included in the additional scans at lower baud rates.

Requirement: The range scanned must have devices with unique primary addresses.

Recommendations:

Consideration: If you have many meters that fully support secondary addressing with wildcard searching, it may be quicker to use the Secondary Address Search Discover.


Single Device Discover

Ensure that only a single device is connected, to ensure that this discovery mode correctly functions. If there is more than one device connected, it will result in collisions, because all meters connected will attempt to reply at the same time.

Requirement: Only a single device is connected.

Recommendations: When it is not known which addressing mode the device supports, it is recommended to try the scan at a slower communications timing first because there are fewer messages used.


Secondary Address Search Discover

In this mode, the system will attempt to identify secondary devices using wildcard scanning. It is recommended to firstly scan with the manufacturer code if known, then falling back to another scan with no filters if no relevant devices are located. When scanning, any filters set will be applied to the criteria devices must match. (Note that any non-matching devices found will mean that those devices are ignoring the set filters and responding anyway).
For each baud rate selected, the driver will perform the following procedure:

1. Identify if any devices respond at the required baud rate.
2. If any device responds, then further scan's are carried out throughout the wildcard range 0FFFFFFF - 9FFFFFFF (F is a wildcard)
3. If there is a collision, the range is narrowed down e.g. 01FFFFFF, 02FFFFFF, ... For example, if multiple devices are in the range 0FFFFFFF.
4. When a single device responds with its data, it is discovered and any remaining possible addresses for devices are scanned.

Note that scans at multiple baud rates, do not exclude previously located devices due to the wildcard nature of the process.

Requirement: Devices must be able to respond to REQ_UD2 with a wildcard address selected, in order for this to discover them.

Recommendations:

Consideration: The wildcards match against ident numbers. If you have many devices from the same batch with incremental idents due to collisions it may be quicker to perform a primary scan if appropiate. Each collision will result in 10 more checks at the next sub-range of the address. E.g. 10 devices with ident's 00000000 - 00000009 will result in 71 messages.

Secondary Address Search Filters

Secondary Discovery Filters Options



When a secondary discovery is carried out, additional filters can be set to limit the scan so that devices are asked to respond only if they fit an extended criteria. If devices ignore this, then they may still appear when they don't match the requested criteria.

Communications Baud Rate

With the exception of when it is scanning the internal device database, all discovery's involve messages that are sent out on the wire to the connected devices. When discovering connected devices, the next step in the wizard is so select the baud rate for the scan.

NOTE: When connecting to an MBus network via a TCP/IP gateway, the gateway determines the baud rate of the communications.
Refer to the gateway's information if you need to modify its baud rate.

When connecting via a serial device, the speed can be determined by the driver. For serial based MBus networks you can therefore select one or more serial baud rates to scan at. Scans are run independently in speed descending order to ensure the highest baud rate speed is selected against a device.
For primary address scanning, if a device is detected at address X (E.g. 5) at 19,200 baud, then address X (E.g. 5) will not be scanned again in lower baud rate scans from the same request.
This does not apply to discovery methods based on secondary addressing, which do not target explicit addresses but use wildcard based scanning.



Device Discovery Baud Rates Dialog

The slower the baud rates are, the higher the overall latency will be for the network due to transmission times.

Customized Comm Timings

On networks with non-identical meter devices installed on the same bus, devices may require alternative transmission timings to ensure that each meter's data is read correctly. These options allow the discovery of devices which may be running at the same timings as other meters.
The timings which were found to be successful in the discovery process are pre-populated in the MBusConfig under the MBusDevice.



Customized Comm Timings Dialog

These settings directly map to the settings under the network, which can be overridden on a per-device basis via the Mbus Config under each device.

Examples of discovery setup

Devices with confirmed timings at Tridium EMEA

Sonex Supercal 531

Primary Search: No special criteria required, standard speed selection.
Secondary Search: The document sourced from Sonex: M-Bus Frames 531 - Rev. 29-03-2010.pdf has been referred to.
This identifies the device as expecting manufacturer number, manufacturer id, ... as part of its selection for secondary addressing. The discovery process therefore requires filters to be set. A suitable option is to set the manufacturer to SON, which the document defines as the Manufacturer ID. Standard speed selection.
NOTE: This device does not respond and therefore will not secondary discover without filters being setup.

Honeywell EEM230-D-M

Primary Search: No special criteria required, standard speed selection.
Secondary Search: No special criteria required, standard speed selection, filtering with Manufacturer ID HON works and recommended.

ABB DEM 13007

Primary Search: No special criteria required, standard speed selection.
Secondary Search: No special criteria required, standard speed selection, filtering with Manufacturer ID ABB works and recommended.

ABB DAM 13007

Primary Search: No special criteria required, standard speed selection.
Secondary Search: No special criteria required, standard speed selection, responds to any Manufacturer ID selection, recommended to filter by Manufacturer ID ABB if other devices exist.

Kamstrup Multical 401 / 601

Common parameters: Set Initalisation delay = 4 seconds because the manual(s) state that the meter(s) takes 3.5 seconds to read, before responding to further communications after normalisation.
Primary Search: Standard speed selection, with common parameters set.
Secondary Search: Slow speed selection, with common parameters set, filtering with Manufacturer ID KAM works.

Specific options to the Mbus Device Manager

The Assign Baud Rate button enables the user to change the baud rate to the slave device so as to obtain optimum performance. Having carried out the discovery, select a device in the lower Database pane. the Assign Baud Rate button is now active and can be selected. Select the required Baud Rate and the system will go and check that the device can receive this new rate. If there is no communication with the slave device after the rate had been changed then the job will return the rate back to the previous one. If this is not possible the MBus default of 300 Baud will be selected.

The Update button enables the operator to update device configuration information from the Network. By selecting the device in the lower Database pane the button will become active. A job will commence and the configuration data for that device will be refreshed by data from the network. This is done via primary addressing, so only devices uniquely addressed with a primary address should have this button used.