Baud rate calibration method and calibration circuit of CAN controller

Abstract

The invention discloses a baud rate calibration method and calibration circuit for a CAN controller, and the method comprises the steps: S1, starting a calibration program, carrying out the calibration, and enabling a calibration module to transmit a data frame with a set length to a tested calibration module; s2, carrying out edge detection on the data frame received by the detected calibration module, obtaining and counting a single-bit high level count value, and then screening out a single extra-high level value for calculation; s3, calculating the selected single extra-high level count value and the count value of the calibration module to obtain the actual frequency of the current clock signal of the tested calibration module, and calculating the calibrated Baud rate according to the actual frequency of the tested calibration module to obtain a frequency division coefficient; and S4, storing the frequency division coefficient in the tested calibration module, and then performing data transmission or / and receiving between the tested calibration module and the baud rate test module to determine whether the baud rate of the CAN controller is successfully calibrated.

Description

technical field [0001] The invention relates to the field of intelligent robots, in particular to a baud rate calibration method and a calibration circuit of a CAN controller. Background technique [0002] Because the CAN bus uses differential signals for data transmission, it has a strong anti-interference ability. At the same time, because it uses a non-destructive bus arbitration mechanism, even if different nodes send data to the CAN bus at the same time, there will be no data confusion. and communication errors, due to the various advantages of the CAN bus, the CAN bus control system is widely used in various types of automation equipment. [0003] In the CAN bus network, the devices or sensors of each node are often diverse. If you want to make the CAN bus communicate normally and stably, you must ensure that the baud rate error between the nodes is kept within the CAN bus. Accept range. Therefore, the baud rate between CAN bus nodes cannot have too large a frequency...

AI Technical Summary

Problems solved by technology

However, when the on-chip RC oscillator is selected, the frequency will cause an error of about ±3% due to external factors such as temperature, and the stability of the frequency is also worse than that of the external crystal oscillator. Setting the baud rate parameters according to the theoretical calculation value cannot guarantee CAN reliability. Communication

The simple way for the CAN controller is to set the CAN nodes to the same baud rate, but this is not very flexible. If the RC error is too large, the CAN nodes may not work properly.

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