Development Of Universal CAN Bus Interface For Well Logging Tool

Design of the data transfer bus interface circuit is one of the key technologies in the new imaging logging system developed. Compared with conventional DTB (Data Transmit Bus) and other means of transmission, the high-speed CAN (Controller Area Network) is a better choice to achieve the data transfer bus interface circuit for well logging tools, with simple structure, high data transfer rate and high reliability.Based on the high-speed CAN2.0B agreement, the functional requirements of the CAN bus interface circuit is analyzed and detailed, and then the functional model for the circuit is established. Based on the theory of circuit availability, an availability model for the circuit is established, and the circuit's availability whose targets are distributed later is top-down forecasted in the thesis. Finally according to the principles of functions and availability of the circuit, a universal CAN bus interface circuit design is proposed to well logging.According to the design, the universal CAN bus interface circuit selects high-quality chip of TMS320LF2407 as the circuit's main processor, high-speed processor downward exchanges data with well logging tools through the dual-port RAM, and upward communicates with CAN bus through the actuator. After reasonable selecting and filtrating of Components, thermal and EMC designing of the circuit PCB and C language programming, the circuit is ultimate realized.At The end of the thesis, the universal CAN bus interface circuit designed is tested by some circuit experiments in the high-temperature environment simulated in the laboratory. The results show that at the working environment with temperature of 155°C, the data transmission rate stability achieves 1Mbit/s between the circuit and CAN bus, and the data exchange rate stability achieves 42.7Mbit/s between the circuit and well logging tools. The lower confidence limit of the circuit's MTBF (Mean Time Between Failures) is 9.1 hours with confidence of 0.9.