NMEA 2000 Actisense Output format

NMEA 2000 Actisense Output format

This is binary formatted NMEA 2000 output

How to enable

Use the web interface, and browse to Settings->Data-Server Settings

Use the drop-down boxes to configure your requirement.

1) Select TCP or UDP mode

2) Select format “N2K Actisense”

3) Select “Transmit Only” (Only transmit available at present)

4) Select the TCP or UDP port on which connections are made

Description

We recommend that software developers support this format “N2K Actisense” or the alternative ASCII format “ASCII N2K” in applications because they are the easiest option for developers – both formats fully decode both fast packet and transport protocol messages so that no need to understand the low-level packet reconstruction of NMEA 2000 is required.

Refer to the NMEA 2000 Appendix B for details of how to decode a PGN’s fields.

Advantages of “N2K Actisense” format

N2K Actisense uses around half the bandwidth to send a similar amount of data when compared to N2K ASCII.  This makes N2K Actisense more suitable for applications which transfer to the cloud.

Disadvantages of “N2K Actisense” format

As a binary format, the N2K Actisense header fields are not easy to read.  The binary contents of each PGN will need an NMEA 2000 viewer application to decode the actual content of each field’s bits & bytes.

Format of N2K Actisense

Once the DLE, STX, ETX and DLE stuffing characters have been removed, messages sent in “N2K Actisense” format have the following form:

<ID><LL><DA><SA><PDUS><PDUF><DPP><C><TTTT><MHS>b0b1b2b3b4b5b6b7…bn

• <ID> BST Message ID
8-bit/1-byte that indicates the message format used for this message.

• <LL> Length
16-bit/2-byte that indicates the payload length, the maximum length of an N2K message is 1785.

• <DA> Destination Address
8-bit/1-byte Location for storing the N2K Destination Address of the device receiving the message.

• <SA> Source Address
8-bit/1-byte Location for storing the N2K Source Address of the device sending the message.

• <PDUS> PDU Specific
8-bit/1-byte Lowest byte of PGN, depending on PDUF this will contain an address (PDU1) or a Group Extension (PDU2).

• <PDUF> PDU Format
8-bit/1-byte PDU Format determines contents of PDUS.

• <DPP> Data page and priority
8-bit/1-byte Data Page and message Priority bits.

• <C> Control
8-bit/1-byte PGN control ID bits and 3-bit Fast-Packet sequence ID.

• <TTTT> Timestamp
32-bit/4-byte relative timestamp (since power on) in milliseconds.

• <MHS> Message header size
8-bit/1-byte Size of message header, includes all bytes up to b0.

• (b0…bn) Message data
Message’s payload of data.