# Setting up BACnet in CODESYS

In order to use the BACnet library, the setup of the BACnet IP datalink and the BACnet server in CODESYS must first be carried out.

## BACnet IP datalink

{% stepper %}
{% step %}
**Add Ethernet interface**

In the device tree the device *Ethernet* is attached. This sets the physical interface for BACnet communication.

<div align="left"><figure><img src="/files/fd66e4b1d87c4932ca73935db495e1e0efec7d3f" alt="" width="375"><figcaption></figcaption></figure></div>
{% endstep %}

{% step %}
**Configure Ethernet interface**

Now the device is configured; the IP address of the target device (i.e. of the own CPU) must be specified. The IP address of the other BACnet participant is determined communicatively (*Who-Is* – request via broadcast telegram X.255).

<div align="left"><figure><img src="/files/39a2811db3645166bf7d2aed02e3b84dcab27bbb" alt="" width="375"><figcaption></figcaption></figure></div>
{% endstep %}

{% step %}
**Add BACnet IP datalink**

In the device tree below the device *Ethernet* the device *BACnet IP datalink* is attached.

<div align="left"><figure><img src="/files/a2e0c55a166607b60fc68bc55aff1160285fc13b" alt="" width="375"><figcaption></figcaption></figure></div>
{% endstep %}

{% step %}
**Configure BACnet IP datalink**

Here the BACnet network number and the UDP port used (default: 47808) are primarily specified.

<div align="left"><figure><img src="/files/419d81615ecfacb18581c846129a69bda9a1dead" alt="" width="375"><figcaption></figcaption></figure></div>
{% endstep %}
{% endstepper %}

## BACnet Server

{% stepper %}
{% step %}
**Add BACnet Server**

In the device tree the device *BACnet Server* is attached. It serves as the BACnet communication hub and must always be present. The client-server principle is applied: the client reads/writes data provided by the server.

<div align="left"><figure><img src="/files/fefeab16824a28e324b08e121116c7ea500421a7" alt="" width="375"><figcaption></figcaption></figure></div>
{% endstep %}

{% step %}
**Configure BACnet Server**

The target device (our CPU) can be operated both as a BACnet server and as a BACnet client (also simultaneously).\
When operating as a BACnet server, the objects (for example a temperature actual value of the target device) are attached as devices beneath the BACnet server. When operating as a BACnet client, the objects are defined in CFC.\
\
Within it the character set used (UTF8) and the option *AutoStart* (automatic start of BACnet communication) are defined

<figure><img src="/files/3506d4d37dd6fb08bd8f04101b1555bcdf75489c" alt=""><figcaption></figcaption></figure>

Furthermore, the properties of the object *Device* (i.e. of the own BACnet server) can be specified here, which another BACnet participant can then read.

<figure><img src="/files/e022f9592ed026cb28d9338f31af016765517ad7" alt=""><figcaption></figcaption></figure>
{% endstep %}
{% endstepper %}


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