How to deal with Modbus communication problem?

Step1: check whether the communication parameter setting is wrong

D8126: communication protocol

D8120: baud rate, stop bit, check mode, etc.

Step2: check whether the communication instruction is wrong

There will be a timeout error report if multiple RS instruction used at the same time, it will have no effect on communication.

Check whether the slave station and operation address are current.

Check whether the Modbus function is wrong.

Step3: check whether the wiring is wrong

Step4: check whether there is electrical interference on site

Keep communication cable away from power cable.

Communication cable use twisted pair shielded cable.

Good grounding.

Step5: check the with third part communication test tool (such as Modbus poll)