1 MODBUS TCP/IP TROUBLESHOOTING1.1. Make sure you can ping the device, verify the IP Address and Unit ID(Modubus ID default is 255) are correct by using ping command in windows. User can ping only to the IP not the ID.
Figure 1. Ping command in windows
1.2. Modbus default port is 502.Please check the following article for the factory settings: https://support.rheonics.com/support/solutions/articles/81000297604-connecting-the-modbus-tcp-outputs
1.3. Try a different cable. If other devices work correctly in the network, swap devices to discard a damaged device, noise or discard broken wiring.
Figure 2. External tool to test ethernet cable
1.4. Avoid duplicate IP address Each slave must be configured with a unique Modbus IP address. The duplication of addresses can cause problems in communication with that address, because both devices try to respond to commands.
2 CRC ERRORS
These errors are easier to deal, it usually means that the device is at least recognizing bit activity on the network line, however the bits probably make no sense to the device. When getting these errors check the following:
• Check to see that Pre-Delay is at least 50 mS.
3 MODBUS DEBUGGING TOOLSModbus Poll is a Modbus master simulator designed primarily to help developers of Modbus slave devices or others that want to test and simulate the Modbus protocol.
https://www.dropbox.com/sh/lv76vwm5lnpy79b/AACL7dhgIydyX_QcV7GK5Ir1a?dl=0