Abstract: The platform construction of FlexRay bus, a new kind of car bus, is introduced in this paper. In the actual platform, the FreeMASTER software of Fresscale is employed to develop PC test software of the test platform of FlexRay bus, by which the properties of FlexRay bus are carried out and tested, including related characteristics of the protocol, characteristics of codec and redundant reliability of communication

Bao Yue

Luo Jie

Wang Pengjie

CiteSeerX

Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 254
  
Sensors & Transducers
© 2013 by IFSA 
http://www.sensorsportal.com 
 
 
 
 
 
 
Platform Construction of FlexRay Bus and Research  
on its Performance 
 
Luo Jie, Bao Yue, Wang Pengjie 
School of Information Engineering, Wu Han University of Technology,  
Wu Han city of Hu Bei Province, 430070, China 
Tel.: +8613476103111, fax: +8602787850513 
E-mail: luo_jie@whut.edu.cn, 215723753@qq.com, 546639064@qq.com 
 
 
Received: 16 September 2013   /Accepted: 15 October 2013   /Published: 23 December 2013 
 
 
Abstract: The platform construction of FlexRay bus, a new kind of car bus, is introduced in this paper. In the 
actual platform, the FreeMASTER software of Fresscale is employed to develop PC test software of the test 
platform of FlexRay bus, by which the properties of FlexRay bus are carried out and tested, including related 
characteristics of the protocol, characteristics of codec and redundant reliability of communication.  
Copyright © 2013 IFSA. 
 
Keywords: FlexRay, Auto bus, Eye diagram, FreeMASTER. 
 
 
 
1. Preface 
 
Among these traditional car buses, the CAN 
(Controller Area Network) bus and its child 
Networks (such as LIN (Local Interconnect Network) 
bus) are widely used today [1, 2]. As auto control and 
communication systems become increasingly 
complex, the require of vehicle is becoming higher 
correspondingly. Especially, with the increase of the 
X-by-wire in the Vehicle control system, it asks for 
higher performance, for instance, transmission speed, 
reliability of, distributed control [3]. Currently widely 
used CAN bus technology is based on the event-
triggered with the highest communication rate up to 1 
Mbps, which yet cannot satisfy the requirements of 
X-by-wire system for high bandwidth and fault 
tolerance. Hence, the new vehicle network bus --
FlexRAy arises as it requires. 
FlexRay bus adopted the data transmission 
technology based on time trigger with data transfer 
rate of up to 10 Mbps, which improves the data 
transmission rate and enhances the high reliability 
requirement. This kind of communication system is 
able to satisfy the future demand of interior control 
application.  
FlexRay protocol is developed by FlexRay 
alliance, initially formulated jointly by 
DaimlerChrysler and BMW to meet their current and 
future product demand. Afterwards, with the join of 
Bosch, NXP, Freescale, GM, Volkswagen and other 
companies, FlexRay protocol has been optimized and 
V2.1 version of FlexRay was published in 2005. 
Based on the ByteFlight protocol by BMW company 
and expanded, FlexRay gains the support of several 
car manufacturers once launched [4-7]. 
Because there has been only seven or eight years 
since the FlexRay protocol was released officially, its 
agreement, related control, and the design and 
production of transceiver chips of physical layer are 
mainly developed by developed countries. In those 
Article number P_SI_465
Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 255
nations with relatively high development of 
automotive electronics research, say, America, 
Germany and Japan, etc., have related research 
achievement. However, for China failed to participate 
in the formulation of the FlexRay protocol standards 
and only a handful of universities and research 
institutes made some theatrical researches and 
experiments on protocol and its applications, the 
research on the FlexRay technology in china is still in 
bud [9]. 
 
 
2. The Build of Hardware Platform  
of FlexRay 
 
The platform of FlexRay adopts MCU 
(MC9S12XF512) of integrated FlexRay protocol 
controller from Freescale company as the main chip 
and TJA1080 from NXP company as FlexRay driven 
chip to build the network nodes and testing platform. 
The function structure of FlexRay node is shown in 
Fig. 1. 
 
 
  
 
Fig. 1. The function structure of FlexRay node. 
 
 
Single + 12 V power supply is employed in 
system node to analog the power supply environment 
of vehicle-mounted ECU. For the sake of the 
convenience of online board debugging (OBD) of 
FlexRay node and scalable networking capabilities, 
many nodes of CAN bus which have already been 
used in the vehicle network are designed in the 
FlexRay nodes, and MC9S12XF512 itself with the 
CAN protocol controller is adopted. Meanwhile, the 
PCA82C250 CAN driver from NXP company is 
employed as the external bus driver. The 
communication between system node and PC uses 
the currently popular USB interface whose high 
speed and the characteristics of supporting hot plug 
greatly facilitate the online capability between system 
and PC, while USB interface chip is PL2303HX chip 
from Taiwan's Prolific company. The hardware 
structure of node is shown in Fig. 2.  
In the design of the FlexRay platform, 4 FlexRay 
nodes are employed to network communication and 
passive bus network topological structure 
recommended by FlexRay protocol is used, 
furthermore, the communication distance between 
nodes is about 1m. Among those 4 FlexRay hardware 
nodes, one as the host node is not only connected to 
the FlexRay bus, and a PC, but also communicates 
with monitoring software of FreeMaster, whereas the 
other 3 FlexRay nodes respectively simulated car 
ECU unit components. And the communication rate 
of the entire network platform is designed up to  
10 Mbits/s with dual channels. 
 
 
 
 
Fig. 2. The hardware structure of node. 
 
 
3. The Software Design 
 
The software of FlexRay node is mainly for 
initialization and parameters setting of FlexRay 
communication controller module of MC9S12XF512. 
After the initialization of MCU, it is able to enforce 
the MC9S12XF512 FlexRay module into FlexRay 
protocol configuration and start FlexRay 
communication controller. Once the start is done, 
check whether FlexRay node synchronizes to 
FlexRay cluster and start the normal FlexRay 
transceiver when finishing the synchronization. The 
Detail flow chart of software main program of 
FlexRay node is shown in Fig. 3. In addition, the 
communication rate, cold start node, communication 
channel, sending and receiving time slot, etc., a series 
of parameters configuration are set by the FlexRay 
controller. For the sake of the  timeliness of node 
communication, communication of FlexRay is 
designed to base on interrupt control transceiver, in 
which FlexRay protocol controller and the 
corresponding transmit-receive of the main program 
will be triggered by the interrupt caused by slot. 
 
 
4. The Test Platform of FlexRay Network 
 
The test platform is designed by 4 independent 
FlexRay nodes (hardware circuit board), one PC 
(running FreeMASTER software), a digital phosphor 
oscilloscope of MSO4104B from Tektronix, a 
switching power supply with +12V / 2A and etc. The 
test platform is shown in Fig. 4. 
The platform is designed of wake up frame with  
60 bus bits of period, TXIdle with 180 bus bits of 
period. And the sending rate of bus is 10 Mbits/s, 
which means the period of bus is 0.1 μs, TxLow = 
Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 256
6 μs, TxIdle = 18 μs. The wake-up frames of FlexRay 
captured by MSO4104B are shown in Fig. 5. As 
shown in Fig. 5a, there are 16 frames sent by the 
wake-up frame according to the program setting. By 
the cursor function of MSO4104B, it is tested that 
TxLow = 6 μs (as shown in Fig. 5 b), TxIdle = 18 μs 
(as shown in Fig. 5c), and the total length of wake-up 
frame TxLow+ TxIdle = 24 μs, which all match the 
protocol and the demand of program design. 
Meanwhile, the period of FlexRray bus is 5 ms, and 
the network period of FlexRay captured by 
MSO4104B is shown in Fig. 6. 
 
 
  
 
Fig. 3. The flow chart of software main program  
of Flexray node. 
 
 
 
 
Fig. 4. The test platform of FlexRay. 
 
 
 
 
 
Fig. 5. The wake-up frame captured by MSO4104B. 
 
 
Meanwhile, the period of FlexRay bus is 5 ms, 
and the network period of FlexRay captured by 
MSO4104B is shown in Fig. 6. As shown in Fig. 6a, 
the period of FlexRay bus is 5 ms measured by the 
MSO4104B cursor function, and one bus period 
includes 4 FlexRay frames corresponding to the slot 
of node 1 ~ 4. The full FlexRay frame captured by 
MSO4104B is shown in Fig. 7a. Through the cursor 
function of MSO4104B, the total length of the frame 
is 41.4 μs and the length of TSS is 1.1 μs (as shown 
in Fig. 7 a and 7 b). The waveform of 24 bits CRC 
check code is shown in Fig. 7c, in which the FES  
(1 bit High + 1 bit Low) at the end of the wave is a 
kind of static frame. 
In order to monitoring signal integrity, we test the 
single's eye diagram at the TP4 test point(at the 
receiving end).The test result showed in Fig. 8, as 
show in the figure, the test eye map large than test  
template. So the platform can be decoding the signal. 
The upper programming of FreeMASTER 
computer from Freescale is used to program the 
principal monitoring software of network platform of 
FlexRay bus. By the monitoring software, it is able to 
monitor the entire performance parameters of 
FlexRay network and communication data, and 
prompt alarm as well when errors and bugs happen. 
The monitoring software interface of FlexRay bus 
platform is shown in Fig. 9. 
 
Chan
nel 
Chan
nel
#1 
#2
1
#3
1
#4
1 
MSO4104B 
oscilloscop
PC 
USB 
Cable 
Pro
be 
FlexRay 
Bus 
+ 12 v 
power 
supply
Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 257
 
Fig. 6. The network period captured by MSO4104B. 
 
 
  
 
Fig. 7. The frame picture captured by MSO4104B. 
 
 
Monitoring software is composed of three 
monitoring windows, including host control window 
(HCW), waveform data window (WDW) and 
parameters of the bus window (PBW). Firstly, the 
HCW is used to monitor the communication status of 
every node of the network and the connection status 
of channel A and B with the indicator lights. 
Meanwhile, there is a ship switch on the interface of 
HCW to be able to stop the communication at any 
time to verify the wake-up function of FlexRay 
network. Secondly, the WDW monitors the various 
parameters of bus, including the statuses of POC, 
wake-up, sync, MTS, real-time data of sent-received 
by the node and channel error counting, etc. Thirdly, 
PBW displays the data wave from the nodes’ sensors, 
aiming at simulating  the steering wheel and  
pedals, etc. 
After connecting each node to FlexRay bus and 
the USB interface of main monitoring node to the 
PC's USB interface, open each node power and then 
start the monitoring software FlexRay bus network. 
The monitoring interface of each node under normal 
operation is shown in Fig. 10. 
 
Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 258
 
 
Fig. 8. The eye diagram test by MSO4104B. 
 
 
 
 
Fig. 9. The running interface of monitoring software  
of FlexRay bus platform. 
 
 
 
 
Fig. 10. The monitoring interface of FlexRay bus platform 
under normal operation. 
 
 
Monitoring software can monitor the physical 
connection condition of dual in real-time and the 
corresponding fault alarm is given. Channel B 
miswires, for example, the status light of Channel B 
changes from green to red and the error-counter of 
corresponding starts counting. As shown in Fig. 11, 
when the Channel A is disconnected artificially, the 
light of Channel A on the monitoring interface turns 
red and error counter starts counting at the same time. 
Experiments on FlexRay implementation of data 
communication with 10 Mbps, each node uses the 
ADC to acquisite corresponding sensor voltage and 
sent which to monitoring node. In the experiments, 
when any channel is disconnected physically during 
communication, the corresponding warm information 
is given and then communication is restored, due to 
the redundancy communication function of FlexRay 
bus, which validates the reliability of FlexRay 
communication. 
 
 
 
 
Fig. 11. The indicator interface of channel error status. 
 
 
5. Conclusion 
 
With the development of modern automotive 
technology, it calls for increasing high performance 
of automotive safety. Considerable increase of the 
number of electronic control unit and sensors 
(especially X-by-Wire system) helps the development 
of vehicle bus and network technology [12]. FlexRay 
network protocol, the next significant generation 
communication network, was launched by the 
alliance of Bosch, BMW, and Daimler - Chrysler, 
Volkswagen and other car manufacturers. And the 
FlexRay provides the development direction of new 
vehicle communication network. Furthermore, the 
deep researches on the protocol and the application 
theories and the establishment network platform to 
analyze the performance of network, all provides the 
essential theories and practical application value for 
the design of next generation of automotive 
electronic security and the researches on vehicle 
communication network system. 
In this paper, the author put forward a method of 
designing a complete communication platform of 
FlexRay bus network and realized the 
communication platform of FlexRay bus network. 
The physical test and verification on the network 
platform of FlexRay bus prove that the platform is 
feasible and stable.  
Compared to CAN, FlexRay bus with a wider 
bandwidth (single channel can be up to 10 Mbps), it 
can guarantee a reliable communication for the 
certain behavior, and be possible for the system 
integration and future extension, which might realize 
the function of drive-by-wire but without mechanical 
back up in the future [13-14]. Meanwhile, the 
FlexRay technology has incomparable advantages 
Sensors & Transducers, Vol. 25, Special Issue, December 2013, pp. 254-259 
 259
over traditional vehicular network and its emergence 
meets the requirement of some core technologies 
called by modern automotive industry. 
 
 
Acknowledgements 
 
This study was supported by International Science & 
Technology Cooperation Program of China (2 0 1 2 
D F A 1 1 1 8 0). 
 
 
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