Download - HANSER automotive

© Carl Hanser Verlag, München www.hanser-automotive.de Nicht zur Verfügung im Intranet- und Internet-Angeboten sowie elektronischen Verteilern
cept provides a better scalability
over functions and car models. For
the distributed navigation application
this architecture concept was
abstracted to two single network
nodes, one for route calculation
including map storage and one for
display purposes.
Prototype System
Overview
Hardware
Fujitsu starter kits have been selected
for the prototype system. One
SK 91F467 FlexRay is used to transmit
the graphic data to the second
node. This second node consists of
an SK 91F467 FlexRay and the
Cremson-Lime starter kit, used for
the display of the received data.
The SK 91F467 FlexRay supports
the 32 bit MB91F467D MCU and
the MB88121 FlexRay communication
controller (CC). In addition, a 4
MB SRAM and a 16 MB Flash have
been specially hooked for the prototype
system and can be addressed
as external memory. The Flex-
Ray transmission uses the AS8221
transceiver from AMS. The graphic
portion of the system is supported
by the Cremson-Lime starter kit,
which comes with an MB86276, a video input processor
(VIP) and 64 MB SD-RAM. Using common plug connections
such as DVI and LVDS, it is easy possible to connect
standard displays. The dataflow is controlled by the
MB91F467D series as the host MCU, which provides three
CAN interfaces, 6 LIN USART and a parallel bus interface.
This interface connects the MB88121 FlexRay CC to the
host MCU. Based on the E-RAY core, licensed from Robert
Bosch [2], the MB88121 CC supports 2-channel operations,
and with more than 8 kB of message buffer memory,
up to 128 different identifiers can be supported. The
device meets the latest protocol specification, as defined
by the FlexRay consortium: 2.1. As the graphic data is received,
it is passed to the MB88276 VIP, which is also connected
to the host MCU via a bus interface.
Software
The prototype system (Figure 3) developed within the feasibility
study contains two FlexRay nodes. The control node
is responsible for accessing the mass data storage device
with the map data and the processing of GPS data for the
route calculation. Due to their complexity, the GPS and
route calculation modules had to be simulated in an easier
way, but this does not really influence the conclusions gained
by this prototype. The simulation is based on a pre-defined
list of points along the route. These points correspond
to a fixed X/Y-position in the whole map source and need
an interpolation algorithm.
SPECIAL EDITION FLEXRAYl AUTOMOTIVE 2008l17
Figure 2a: A central gateway architecture with FlexRay
Figure 2b: FlexRay communication backbone architecture
© automotive
© automotive
The second node has been called the display node. It processes
the received commands and map data and changes
the information on the connected display accordingly.
When the navigation starts, the map of the current position
is completely transferred only once. As the position of
the vehicle changes in the simulation, new sections of the
map must be displayed. In order to reduce the required
bandwidth for the graphic data transmission the whole
map is not transferred at every change. Instead, only the
new pixel rows and/or columns are transmitted. The display
node receives a command to scroll down the appropriate
number of pixels on the displayed map in the appropriate
direction and fills the gaps in this new map section with the
received row or column of graphic data. Such a command
could look like ‘move map in +X direction for the distance
of two pixels’. The old data that is no longer used in the
display is not retained to reduce the memory requirements
of this node. If, during this process, an error occurs, a complete
part of the map will be sent to the display node so
that an error-free display is realised.
As well as the graphic information, command and control
data is also transferred. For example when the information
to turn in another direction is sent, the display node will show
a pop-up window in the display with an arrow indicating the
new direction. This command and control data of the control
node and the responses of the display node are all transferred
in the static segment. The graphic data uses the dyna-