
TT400 WirelessHARTTM – Operation, Maintenance and Instruction Manual
VIII
the network that requested services to it, as well as manages the routes between the devices on the
mesh network.
Specifically, about the joining process of a WirelessHART device to the network, the Network
Manager validates the Network ID and the Join Key attributes which are configured in the
WirelessHART Gateway and WirelessHART devices.
The Network ID identifies a WirelessHART network in unique way. It is an unsigned integer attribute
and must be configured on the WirelessHART Gateway and all WirelessHART devices. Considering
a WirelessHART network installed in a plant, the permitted values for the Network ID ranges from 0
(hex 0x0000) to 32767 (0x7FFF hexadecimal).
The Join Key is a security key used to encrypt joining requests from WirelessHART devices that
receive the advertisement with the Network Id identical to theirs. It may be single or each
WirelessHART device may be configured with an individual Join Key. In the first case, the
WirelessHART Gateway and all WirelessHART devices must be configured with the same Join Key.
In the second case, which provides higher communication security level, (a) must be configured in
the WirelessHART Gateway a list with individual Join Keys, i.e., a key for each WirelessHART
device, and (b) you must configure each WirelessHART device with its individual Join Key. The Join
Key is a hexadecimal string of 16 bytes. There is no restriction to the hexadecimal value of each
byte. The table below shows examples of some join keys.
16-BYTES HEXADECIMAL STRING
00000000000000000000000000000000
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
00000000000000000000000000000302
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x02
00000000FFFFFFFF0000000000000000
0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
550000000000000000000000000000AA
0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xAA
WirelessHART device
The WirelessHART field device is the device that connects to the process, being able to receive
and/or transmit data on the WirelessHART network. It is a WirelessHART router (repeater) by
nature, i.e., it is able to retransmit messages to/from other devices on the WirelessHART network.
WirelessHART Adapter
It is a bridge-type device, because it is able to provide data of HART + 4 to 20mA field device,
legacy, to the host via WirelessHART. The adapter uses HART FSK standard communication,
wired, to access data from HART field devices. And the adapter also uses the WirelessHART
communication to provide data of the field device to the host. The adapter thus enables a HART
field device to work on WirelessHART network.
We recommend a visit to the HART Communication Foundation website for additional information
about the WirelessHART protocol such as WirelessHART project planning, positioning of devices,
commissioning and verification tools, and practices.
Planning an WirelessHART network
The planning of a WirelessHART network is a task that is very similar to the activities that currently
we perform with conventional wired devices. Furthermore, due to the simplicity of a mesh
WirelessHART network, is exempt, in general, detailed field surveys, which are usually needed
when we plan networks based on other wireless technologies.
Basically, a WirelessHART network involves planning, design, installation and commissioning
phases.
Planning
This phase requires the execution of the steps below:
Scope definition
Clearly define the scope of the network. Answer the question: why do we need the wireless
network? To monitor process variables or to implement a non-critical control? The answer to this
question will facilitate the understanding between the team members responsible for the network