Aiming at the need of CAN bus communication quality, testing and verification, as well as the complexity of traditional CAN analyzer, and the necessity of selecting PC as the display terminal, a CAN bus analyzer design based on ARM microcontroller and smart phone is demonstrated. The analyzer adopts the hardware circuit with ARM single chip as the core to complete the real-time data collection and monitoring of the CAN network; the Bluetooth communication method is used to realize the communication between the analyzer and the smart phone and the smart phone is used as the terminal to complete the data analysis. The article designs the hardware, software and smartphone pages of the analyzer, and proposes a new automatic detection method of baud rate. Finally, the actual test results of the designed CAN bus analyzer are given, and the CAN bus wave can be realized. Automatic rate detection, normal monitoring and CAN bus status analysis.
CAN (controller area network) controller local area network is a serial data bus with strong real-time performance, good flexibility and high standardization. It is widely used in automotive electronics, industrial automation, marine, medical equipment, industrial equipment and other fields. Its test equipment CAN network analyzer has become a must-have device for developers. With the easy-to-use CAN bus analyzer, you can quickly find the design flaws or abnormal interference problems that occur in the CAN bus system, and eliminate faults and problems.
The traditional CAN analyzer needs to connect the computer to the CAN analyzer via USB, and then connect the bus under test to the CAN analyzer through the DB9 interface. Since the CAN bus is a field bus popular in the vehicle industry, such a debugging method is inconvenient for a vehicle that requires a road test, and it is difficult to ensure that it can work normally. Similarly, in the field of industrial control, the traditional CAN analyzer has a connection between the two sections, and the industrial scene with more bundles may cause some confusion. In addition, today's devices using the CAN bus sometimes have more than one bus in order to ensure security. Traditional analyzers have at most two interfaces, which means that you need two USB interfaces when you want to test more than two CAN buses at the same time. These two CAN buses are far apart and require a long USB cable. To this end, a Bluetooth CAN bus analyzer with low cost, small size, simple structure, wireless debugging and low environmental requirements is introduced.
1 hardware design
1.1 Overall design
Aiming at the shortcomings of traditional CAN analyzers, this paper proposes a new CAN analyzer that uses a smart phone instead of a PC as a display terminal, uses Bluetooth wireless transmission instead of USB cable transmission, and comes with a lithium battery. The overall design structure is shown in Figure 1.
Figure 1 Block diagram of the overall design of the Bluetooth CAN analyzer
Since the CAN analyzer is a communication protocol with high baud rate and requires complex arithmetic processing for communication quality analysis and fault location, the Bluetooth CAN analyzer proposed in this paper contains three parts in the overall design: ARM is the processing core of the processing core, responsible for CAN bus baud rate detection, data acquisition and Bluetooth communication signal transmission; the second part is lithium battery, responsible for providing power to the motherboard, lithium battery voltage is 5V, capacity is 3 000mAh, size is 11.6mm X42mm & TImes; 69ram, can guarantee the system works more than lOh; the third part is the smart phone, which is responsible for receiving CAN bus data and processing data.
1.2 Motherboard design
There are 4 modules on the main board, which are isolated CAN interface module, ARM processor module, Bluetooth serial port module and power circuit module. The design block diagram is shown in Figure 2, and the physical diagram is shown in Figure 3.
The isolated CAN interface module is responsible for transmitting the ARM data to the CAN bus and transmitting the data on the CAN bus to the ARM processor.
Figure 2 motherboard system design block diagram
Figure 3 motherboard purchase map
The ARM processor module is the heart of the analyzer and uses NXP's LPC2119 processor. The LPC2119 is based on a 16/32-bit ARM7TDMI-STM CPU that supports real-time emulation and tracking, with 128KB of embedded high-speed flash memory and two internal CAN controllers. Its main features are: data transfer rate on a single bus up to 1MB / s; 32-bit register and RAM access; compatible with CAN2.0B, IS011898.1 specification; global acceptance filter can identify all 11-bit and 29-bit identifiers; The acceptance filter provides Full CAN-style automatic reception for the selected standard identifier. It is mainly responsible for processing the data on the CAN bus, and then sending it to the mobile phone through the Bluetooth serial port. In addition, the ARM module is also responsible for detecting the baud rate on the unknown CAN bus and transmitting it to the mobile terminal.
The Bluetooth serial port module is responsible for exchanging data between the ARM and the mobile phone, and the serial port communication rate reaches 1 382 400 bps. The power module is responsible for powering each module.
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