LonTalk communication protocol

Supported device types and versions
Communication line configuration
Communication line protocol parameters
Communication station configuration
Communication station parameters
I/O tag configuration
Literature
Changes and modifications
Document revisions

Supported device types and versions

The LonTalk communication protocol supports communication with 3150 and 3120 "neuron" chips of the LonWorks technology from the Echelon company by means of reading/writing values of network variables. The communication is performed by means of the RNI interface (SLTA, PCLATA, iLON-10, ...) and the standard Win NT system driver, which is installed after installing the "Echelon OpenLDV". This driver can be obtained from http://www.echelon.com/. Versions known to work are "Echelon OpenLDV 4.0" and "Echelon OpenLDV 5.0". Communication has been verified these interfaces:

SLTA/10
PCLTA/10
iLON-10
SmartServer 2.0 Controller
U10 USB Network Interface

Data exchange is performed by the SNVT set (Standard Network Variable Types) and by several user types.

Communication line configuration

Communication line category: LONWORKS

Communication line parameters

Communication line configuration dialog box - tab Protocol parameters.
They influence some optional protocol parameters. The following line parameters can be set:

Tab 1

Parameter

Meaning

Unit

Default value

Full Debug

High level of the communication tracing. It shows the read values of I/O tags and other debug information.

YES/NO

NO

Open/Close Interval

A time interval. After it passes, a re-open action over the interface will be done. 0 (zero) disables this function.

min

0

Communication station configuration

Communication protocol: Echelon LonTalk.
The station address (node) consists of the required address parameters (i.e. "Subnet/Node Addressing"):

Domain is a domain number (0 or 1).
Subnet specifies a network ID (0 up to 255), as a decimal number.
Node is a node number in the network (0 up to 127), as a decimal number.

Neuron ID is an optional address parameter. If it is defined, this address executes the polling of the network variables of node. Neuron ID address is in the hexadecimal form.

If it is necessary to send a network variable value with another address type than "Subnet/Node Addressing", you can configure Group or Broadcast address parameters.

"Group Addressing" parameters:
- ID specifies a group ID in the domain (the decimal number ranging from 0 to 255).
- Member is a member ID of a target node in this group (the decimal number ranging form 0 to 63).
- Size is a group size (2 up to 64). The group size is unlimited when you set 0 (zero).
"Broadcast Addressing" parameters:
- Subnet defines a network ID to which a broadcast message is sent. Set a required value Domain.
- Backlog is an estimated number of ACKD responses or request/response messages.
  
  Parameter description from the literature 1: This field specifies an estimate of the channel backlog that would be created by an acknowledged or request/response message broadcast using this address. It should be set to the expected number of acknowledgements or responses. For example, this might be the worst case number of nodes expected to respond to a message on a channel. If this is unknown, this field can be set to zero in which case a backlog of fifteen is assumed.

Station protocol parameters

They have effect on some optional protocol parameters. The following station protocol parameters can be defined:

Table 1

Full name	Meaning	Unit	Default value
Rpt_timer	Value of the parameter is written into the address array SendAddrDtl when the packets "Poll request" and "Write NV value" are sent. See the Note 1. Parameter description from the literature 1: This field specifies the time interval between repetitions of an outgoing message when unacknowledged–repeated service is used.	-	3
Retry	Value of the parameter is written into the address array SendAddrDtl when packets "Poll request" and "Write NV value" are sent. See the Note 1. Parameter description from the literature 1: This field specifies the number of retries for acknowledged, request/response, or unacknowledged–repeated service (0–15). The maximum number of messages sent is one more than this number.	-	1
Tx_timer	Value of the parameter is written into the address array SendAddrDtl when packets "Poll request" and "Write NV value" are sent. See the Note 1. Parameter description from the literature 1: This field specifies the time interval between retries when acknowledged or request/response service is used. The transaction retry timer is restarted when each attempt is made, and also when any acknowledgement or response (except for the last one) is received. For request/response service, the requesting node should take into account the delay necessary for the application to respond when setting the transaction timer.	-	3
Response Timeout	Timeout for receiving the respond on the polling demand. Total time is tx_timer * retry + Response timeout.	ms	500
Write ACK Timeout	Timeout for receiving the confirmation of sent packet with a new value. Total time is tx_timer * retry + WAT.	ms	1500
Write ACK Immediately	If its value is YES, writing new values into the network do not wait for confirmation (with Writte ACK Timeout). They are immediately acknowledged as received.	YES/NO	YES
Skip Reading after Failed Polling	If the value is YES, the reading of I/O tag values is stopped by the polling on the given station (node). It helps to speed up the value reading form the network variables when some nodes do not communicate (they are switch off). The communication is not delayed because of waiting on the responses of polling from non-functional node. The polling always starts properly but after the first error in reading by polling the reading of remaining network variable interrupted and next node is read.	YES/NO	NO