In the driver's motor vehicle examination system, it is necessary to combine information such as lights, clutch, foot brake, hand brake, seat belt, door switch, horn, wiper, ignition status, engine speed, vehicle speed, gear, frame number, etc. It is necessary to collect data through the automobile OBD to comprehensively judge whether the driver can reasonably control the vehicle according to the actual road conditions during driving.
In the driving test mode, according to the actual use, most driving test system terminals will use the broken wire method to obtain the on-board signal. This method is time-consuming and time-consuming. There are hidden dangers for safe driving. For the signals mentioned, external sensors are usually used to obtain the signals. Although the signals can also obtain in-vehicle data, it also increases the BOM cost and daily maintenance.
Based on the OBD interface and CAN bus acquisition mode, according to the topology of the vehicle's CAN bus, the dual CAN redundant design working mechanism, hardware block diagram and software flow, Su Ruide has undergone a lot of practice in the vehicle's signal acquisition module of the intelligent driving test system. It is proved that the stability, integrity and simplicity of data are effectively improved.
In the design of the EST558S intelligent OBD data collection terminal, through intelligent algorithms, it realizes vehicle identification and automatically switches CAN bus protocol. This is the driving test OBD module of the latest artificial intelligence algorithm currently used in the intelligent driving test system. In the driving test models in this field, there are currently two types of CAN bus networks, one is a high-speed CAN with a rate of 500kb / s, and the other is a low-speed CAN with a 100kb / s body system. It will be distributed throughout the body electronic control unit. Such as electronic fuel injection devices, instrument display devices, ABS devices, airbags, power doors and windows, active suspension and so on. Connected together through the CAN bus network, the data of all sensors on the vehicle, the bus messages of the body control unit, the instructions, the display content of the instrument display unit, etc. all interact on the bus network. After testing, in most models, the instrument panel data needed in the driving test industry exists in the high-speed CAN. To this end, only need to hang the OBD signal module of the artificial intelligence driving test system on the CAN bus, and monitor the data stream to analyze the data to extract the required data.
In design, the STM32F105 is used as the MCU, which uses the ARM32-bit Cotex-M4 core, which has a main frequency of up to 178MHz, an instruction operation capability of 210DMIPS, and two CAN2.0 interfaces. CAN transceiver adopts NXP isolation module, which has extremely high electromagnetic interference EMI and extremely low electromagnetic radiation EME. When the system is powered on, one of the CAN channels is set as the master CAN, and the other CAN channel is set as the slave CAN. The software passes the honor judgment function module to monitor the CAN system status in real time, and detects bus errors such as line failure Abnormal and other states, perform corresponding redundant operations to ensure the normal communication of the entire system and improve the reliability of the system. Redundancy design adopts parallel redundancy mode, that is, two CANs enter the working module at the same time. When both are working normally, the master CAN information is discarded and the slave CAN information is discarded. When the master MCU is not working properly, it switches to the slave CAN in real time. Ensure that the system can work continuously and steadily.
In the early stage of use, because the OBD signal acquisition module of the Sudoku artificial intelligence driving test system was not used, when the CANBUS failed, the driving test process was interrupted, causing a huge impact. After changing to the artificial intelligence driving test OBD module, it has been widely used in driving test models. At present, it is used steadily in Santana, Jetta, Roewe, Elysee, Ease, Geely and other models, reducing the risk of failure. Compared with the traditional acquisition method, the OBD acquisition module based on CANBUS has the advantages of fast and reliable data acquisition, simple installation method, convenient maintenance, and strong anti-interference ability.
AT command command function command description
ATBUD Set the serial port baud rate
The next restart will take effect
ATBUD = 0: Set the baud rate to 9600
ATBUD = 1: Set the baud rate to 38400
ATBUD = 2: Set the baud rate to 115200
ATCAR calibration model
After the calibration is successful, the device automatically
Reboot
ATCAR = 0: Standard OBD, only read vehicle speed and speed, support K
Line and CAN line
ATCAR = 1: New Jetta / New Santana (2019…)
ATCAR = 2: Volkswagen Skoda Xinrui (2019 ...)
ATCAR = 3: New Elysee / New Peugeot 301
ATCAR = 4: Southeast V5
ATCAR = 5: BYD F3 (not supported yet)
ATCAR = 6: GAC Trumpchi GA5
ATCAR = 7: Southeast Mitsubishi Windis
ATSLEEPON automatically enters sleep after turning off the flame
ATSLEEPOFF Turn off the auto-sleep vehicle and do not go to sleep after the engine is turned off. The DT data stream is always broadcast.
ATSLEEP immediately enters the sleep device, immediately enters sleep, waiting for the car to wake up
ATEHZ Set engine data transmission
Intervals
ATEHZ = 5: Set the broadcast frequency 5Hz (200ms)
ATEHZ = 2: Set the broadcast frequency 2Hz (500ms))
ATEHZ = 1: Set the broadcast frequency 1Hz (1000ms)
ATWST restart device
ATINFO Get vehicle information data stream and immediately return vehicle information data stream
ATEDT Get real-time data stream and return real-time data stream immediately
ATBDT gets the status data stream and immediately returns the status data stream
ATGPIO gets the IO port data stream and immediately returns the IO port data stream Table
1 Key status x OFF, ON
2 Battery voltage 0 ~ 20.0 V 1 decimal
3 Speed 0-65535 Unit: rpm
4 Vehicle speed 0 – 255 Unit: km / h
5 gears x manual transmission
MN => Neutral
M1-M5 => 1-5
MR => reverse gear
Automatic car
AP => parking gear
AN => Neutral
AR => reverse gear
AD => travel file
A1-A5 => Manual 1-5 gear
Gear
6 Accelerator pedal 0-100 0 => not stepped on; 100 => fully throttled (percentage)
7 Steering angle n Left turn L0-100, right turn R0-100 steering wheel (percentage)
8 Total mileage 0 – MAX km without decimals
9 Remaining oil volume 0 – 255 L Table 2-EDT data flow
