BACnet/IP

The BACnet/IP driver reads and writes objects of building automation controllers: air handling units, chillers, room controllers and meters. For what all drivers have in common, see How drivers work.

Protocol and role

Role	Client. YTCC reads and writes properties of BACnet devices; it is not a BACnet device itself.
Transport	BACnet/IP over UDP. Devices on MS/TP are reached through their BACnet router.
Default port	47808 (UDP)
Devices per driver	One driver is one BACnet network (local address and port) with any number of devices.
Driver type	BACnet (bacnet)

Driver parameters (network)

Set these on the driver in Drivers → devices.

Parameter	Default	Meaning
Local IP	0.0.0.0	Local network interface; 0.0.0.0 uses all.
Local port	47808	Local UDP port. With another port, devices' broadcast answers are not received: use a fixed Host per device or a BBMD.
Broadcast	255.255.255.255	Address for Who-Is. On Windows use the directed broadcast of the network, for example 192.168.1.255.
Bbmd	empty	Foreign device registration, as JSON: {"host": "…", "port": 47808, "ttl_s": 600}. Who-Is then goes through the BBMD.
Max requests per s	200	Most confirmed requests per second on the network.
Router requests per s	50	Most requests per second to devices behind one router.
Cov lifetime (s)	600	Lifetime of COV subscriptions (60–86400).
Cov confirmed	off	Ask for confirmed COV notifications.
Cov verify (s)	300	Extra read of COV signals at this interval, in case a notification was lost.
Apdu timeout (ms), Apdu retries	3000, 3	Wait and repeats for a confirmed request; a device can override them.
Who is chunk	100	Device instances covered by one Who-Is during a scan.

Changing a network parameter reopens the UDP socket; devices reconnect after a moment.

Device parameters

Parameter	Default	Meaning
Device instance	— (required)	Instance of the device object, 0–4194302. Unique in the driver.
Host, Port	empty, 47808	Fixed address of the device. Empty: the address is found with Who-Is / I-Am. For a device behind a router: the router's address.
Dnet, Dadr	empty	Network number and MAC address behind a router (for example MS/TP MAC 0A); both together, with Host.
Max apdu, Segmentation	from I-Am	Override what the device reports.
Max in flight	2	Read requests at the same time; use 1 behind an MS/TP router.
Apdu timeout (ms), Apdu retries	from the network	Override for this device.
Poll (ms)	1000	Read period for signals without their own scan class.

The help mark next to each parameter shows a short description.

Signal address

Set the address on the Value source tab of the signal, under Address — BACnet:

Field	Meaning
Object type	Analog-input, Analog-output, Analog-value, Binary-input, Binary-output, Binary-value, Multi-state-input, Multi-state-output or Multi-state-value
Instance	Object instance, 0–4194302
Property	Present-value (85)
Array index	For array properties; empty for none

In import files, write the numeric object type and the instance separated by a colon, for example 0:1 (analog input 1) or 5:12 (binary value 12). Other object types (for example integer-value 45, large-analog-value 46) and other properties can be set in Advanced: raw params (JSON) or come from a device scan.

Values

BACnet value	Value in YTCC
Real, Double	Float32, Float64
Boolean; Enumerated of a binary object	On or off
Enumerated (other), Unsigned	UInt32
Signed	Int32
CharacterString, date, time	Text

Reading

Signals are polled by default: Present_Value, Status_Flags and Reliability are read together with ReadPropertyMultiple (ReadProperty if the device does not support it), and requests that are too large are split.

COV (change of value) can be used for Present_Value without an array index: set "receive": "cov" in Advanced: raw params (JSON), or choose COV when you create signals from a scan. The driver subscribes with Cov lifetime (s), renews at 60 % of it, and reads the value again every Cov verify (s). A device that refuses the subscription is polled instead.

Writing

A BACnet signal is written with WriteProperty at a priority (default 8, 1–16). Writing an empty value (relinquish) releases the priority again; YTCC relinquishes at the priority of the last command it sent.

caution

A BACnet signal is written when its direction is out or inout; a signal whose direction is in rejects every command. Set "direction": "inout" (and, if needed, "write_priority": 8) in Advanced: raw params (JSON), or create the signals from a device scan with Read + write.

• Analog objects are written as REAL, binary objects as ENUMERATED (0 or 1), multi-state objects as UNSIGNED.
• After a successful write, the value is read back at once.
• A refusal of the device is shown with its error, for example property/write-access-denied. A device that does not answer is checked with a read; only if that also fails is it marked not connected.

For how operators send and confirm commands, see Send commands.

Quality

Device state	Quality in YTCC
FAULT in Status_Flags, or Reliability not "no fault detected"	Bad
OUT_OF_SERVICE	Uncertain
OVERRIDDEN	Good · Substituted
IN_ALARM	Good (an alarm of the device is not a fault)
none	Good

When a device does not answer, all its signals are Bad · Not connected and keep their last value; the other devices are not affected. The time of a value is the time it was read.

Reconnecting

A device that does not answer after Apdu timeout (ms) × Apdu retries is marked not connected and tried again after 1 second, doubling the wait up to 60 seconds.

Device scan and EDE import

In Drivers → devices, select the BACnet driver and click Scan / EDE:

• Scan sends Who-Is for a range of device instances (or a list of devices), reads the object list of each device that answers, and the names, descriptions and units of its objects. A range of 0 – 0 asks every device.
• Upload EDE reads an EDE file (EDE 2.x, separated by semicolons, up to 64 MB) instead.
• The result shows each object as New, In system or Missing on device. Select rows and click Create signals from selection; choose the signal type, area, receive mode (Periodic or COV) and direction (Read only or Read + write). A dry run shows the changes before they are applied.

One scan or upload runs per driver at a time, and a scan stops after 30 minutes.

Diagnostics

Read now on the Value source tab sends one ReadProperty for the address and shows the value and its type, or the error as class/code, reject: … or abort: ….

The Communication diagnostics panel of the device (see Check the communication of a device) counts under Timeouts / retries every confirmed request that got no answer within Apdu timeout (ms), and every repeat of it. Requests of a device scan are not counted.

Symptom	Likely cause
No device answers	UDP port 47808 is used by another program; on Windows, broadcast 255.255.255.255 leaves through one interface only
Devices in another subnet are not found	Use a BBMD (Bbmd) or fixed Host addresses
Devices behind an MS/TP router time out	Set Dnet, Dadr and Max in flight 1
Signal Uncertain	The object is out of service
Command rejected as Signal is not writable	Direction is in; set out or inout as described under Writing

Supported BIBBs

BIBB	Supported
DS-RP-A ReadProperty	Yes
DS-RPM-A ReadPropertyMultiple	Yes
DS-WP-A WriteProperty (priority, relinquish)	Yes
DS-COV-A SubscribeCOV	Yes
DM-DDB-A dynamic device binding (Who-Is / I-Am)	Yes