Transcript SDP 2_0x

SDP 2.0
System Data Protocol
Overview
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What is SDP?
Provider/Subscriber Pattern
SDP Components– Part 1
SDP Simple Usage
SDP Messaging
SDP Components– Part 2
SDP Messaging
What is SDP?
• System Data Protocol (SDP) is a bidirectional
message protocol for transmitting dynamic
data.
• SDP uses a subscription mechanism allowing
the right data to be sent at the right time
(reduces bandwith).
• SDP messaging allows many-to-many (peer to
peer) communication.
Provider/Subscriber Pattern
• The provider/subscriber pattern defines a one-tomany, unidirectional flow of information.
• The provider has information or events that need
to be communicated to other objects, its
subscribers.
Subscriber
Provider
Subscriber
Subscriber
SDP Components – Part 1
• SDP Provider
• SDP Subscriber
SDP Provider
• The SDP Provider waits for
subscribe messages.
• Once a subscription has
been accepted, the
provider starts sending
data messages to its
subscribe/unsubscribe/request/query
client.
data/acknowledge/revoke/provide
• When the client no longer
requires the data it sends
an unsubscribe message,
the provider stops sending
data messages.
SDP Provider
SDP Subscriber
• The SDP subscriber
sends out subcribe
messages when it
requires data of a
specific type (each data
type has a unique ID).
• The SDP subscriber
consumes (uses) the
arriving data.
SDP Subscriber
data/acknowledge/revoke/provide
subscribe/unsubscribe/request/query
SDP Simple Usage
Subscriber
subscribe/unsubscribe/request/query
data/acknowledge/revoke/provide
Provider
SDP Message Types
Subscriber Messages
• subscribe = 0
• unsubscribe = 1
• request-data = 2
• provide-query = 3
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Provider Messages
acknowledge = 4
revoke = 5
data = 6
provide = 7
(range 0-7 requires 3 bits of information, this is the first part of the SDP message header)
Packed / Unpacked Messages
• For increased efficiency, two different message
strategies are allowed between SDP components:
– Unpacked Messages (objects):
Send objects around (pointer to struct containing data fields).
Used internally within the same executable.
– Packed Messages (serialized data):
Send byte arrays containing a serialized version of the message.
Used between executables (network, data links etc.)
Messaging Example - SDP on CAN
• Only a single CAN frame is required for transmitting
data values up to 32 bits in length (uint8, uint16,
uint32).
• Using ISO-TP as the default CAN transport protocol
allows data values up to 4095 bytes to be sent.
ISO-TP header (1 byte): Single Frame (SF), data-length= 7
SDP header (3 bytes): message-type = data, data-ID = 0x0101
Data Value (4 bytes): uint32 value = 0x1234
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
SDP Components – Part 2
• SDP Gateway
• SDP Router
SDP Gateway
• An SDP gateway routes data between an SDP network
and some other data format and/or network.
• A gateway (usually) has both a provider and subscriber
sub-component (as seen below).
subscribe/unsubscribe/request/query
data/acknowledge/revoke/provide
Subscriber Provider
SDP Gateway
other data format or network
SDP Gateway – Examples
Subscriber
Subscriber
Provider
Provider
Subscriber
Provider
SDP Gateway
SDP Gateway
SDP Gateway
CAN signal read/write
ISO-TP transmit/recv
Serial Link send/recv
Serial Link
CAN Bus
Subscriber
Provider
Subscriber
Provider
Subscriber
Provider
SDP Gateway
SDP Gateway
SDP Gateway
GX Engine HFAL*
signal read/write
socket send/recv
Graphics Engine
RTE
TCP/IP
*) HFAL: HMI Framework Adaptation Layer
SDP Gateway - Benefits
• Each gateway can be designed, implemented
and tested in isolation.
• Standardized communication method in one
end (SDP messaging).
• High reusability: gateways can be connected in
many different configurations.
• Follows the Unix philosphy:
”Do one one thing and do it well.”
SDP Router
• Providers, subscribers and gateways can be connected together
to form networks.
• The SDP router allows SDP messages to flow between SDP
components with low latency.
• Routing tables are by default dynamically maintained (just plug
in your components).
SDP Router
Provider
Subscriber
Provider
Provider
Subscriber
Subscriber
Provider
Gateway
other data format
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Provider
Subscriber
Subscriber
Example Network 1
Application Software 1
(ECU 1)
Application Software 2
(ECU 2)
Router
Router
Subscriber
Subscriber
Gateway
Gateway
CAN Bus
Subscriber
Provider
Example Network 2
Vehicle Processor
Graphics Processor
Router
Gateway
Router
Gateway
Gateway
Gateway
Graphics Engine
RTE Signals
Serial Link
Network 2 without router
(optimization)
Vehicle Processor
Graphics Processor
RCCL / RTE
Graphics Engine
signal read/write
Gateway
Provider
Subscriber
Subscriber
Provider
GX Engine HFAL
Gateway
Provider
Subscriber
Subscriber
Provider
Gateway
Gateway
serial link send/recv
serial link send/recv
Serial Link
Serial Link