Pymodbus Error: 'Unable to decode request' - Troubleshooting Guide - 常规

This error occurs when the data received by the Modbus client cannot be decoded. This could be caused by several issues, such as:

Incorrect data formatting: Ensure the data being sent and received is formatted correctly according to the Modbus protocol specifications.
Incorrect Modbus function codes: Verify that the function codes used in the communication are valid and correspond to the intended operations.
Faulty connection: Check the connection between the Modbus client and the device. Ensure that the connection is stable and reliable. If using a network connection, test for network connectivity and potential packet loss.

Troubleshooting Steps:

Check Modbus settings: Verify that the Modbus settings on both the client and server sides are correctly configured, including baud rate, parity, data bits, and stop bits.
Inspect data formatting: Analyze the data being sent and received to ensure that it complies with the Modbus protocol. Use a Modbus analyzer or logging tools to capture and examine the data.
Verify function codes: Ensure that the Modbus function codes used in the communication are valid and match the expected operations. Refer to the Modbus protocol documentation for a complete list of function codes.
Test connection stability: Conduct connection tests to assess the reliability of the communication channel. Check for network issues or potential packet loss. If using a physical connection, ensure that the cables are properly connected and free from damage.
Consider other factors: In some cases, the error could be caused by hardware problems or configuration issues on the Modbus device itself. Refer to the device documentation for troubleshooting guides and potential solutions.