User manual

AOAA Kit – Software User’s Guide
Page 40
Copyright 2012 © Embedded Artists AB
7.2 EACAN Format
The EACAN format is described below and how it is associated with the CAN frame format. The DLC
field is removed for simplicity. It is not necessary to know about this field and how it is used when
describing the EACAN format.
Figure 37 – EACAN Format
 Dest Addr: This is the same as the CAN identifier and determines where to send the
message.
 Src Addr: The first data byte is used as source address specifying who is sending the
message (meaning that only 8 of the 11 bits in the identifier filed may be used).
 Flags: Message specific flags, see following sections.
 Msg ID: Message identifier
 Data: 0-6 bytes of data where the content and format depend on the specific message.
7.2.1 Broadcast Messages
Since all CAN nodes on a CAN network can see all messages a range of identifier values have been
assigned as broadcast (or common) messages. All EACAN Nodes should listen to and respond to
these messages.
The identifier range 0x00 to 0x0F is considered to be broadcast messages. The table below
describes the available broadcast messages.
Name
Value (Dest Addr)
Discover
0x01
7.2.2 Directed Messages
Most of the messages sent on the EACAN network are directed messages, which mean that they are
sent to a specific receiver. For these messages the identifier field contains the specific receivers ID
(address). The table below contains a summary of all the messages that have been defined for the
EACAN protocol and their message ID.
Name
Value (Msg ID)
Get
0x1
Set
0x2
Subscribe
0x3
Unsubscribe
0x4
Value
0x5
Poll
0x6
ID
DLC
Data
Dest Addr
Src Addr
Flags
Msg ID
Data (message specific)
1 byte
1 byte
0-6 bytes
11 bits