About Modbus TCP
Posted: 11 Mar 2020, 12:47
We can see that it is possible to do Modbus RTU master as the RevPi Connect has the on-board RS485 port, but we are not sure how we can then map the Modbus RTU data to the Ethernet/IP gateway module.
Do you have any information on how to map data addressing between on-board Modbus RTU RS485 port and the Ethernet/IP gateway? (or other gateway such as PROFINET).
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EtherNet/IP is the protocol supported by Allen-Bradley PLC’s and also some other PLC manufacturers, it is not the standard TCP/IP protocol supported by standard Ethernet ports and regular devices. From what I can tell the onboard Ethernet ports on the RevPi support EtherNet/IP protocol.
We need to read data from the Modbus RTU slave into the RevPi acting as Modbus RTU master. Then we need to read data from the RevPi which is acting as EtherNet/IP Adapter (slave) into the external PLC which is acting as EtherNet/IP Scanner (master).
Some more info here about difference between EtherNet/IP and regular TCP/IP communications
https://www.rtautomation.com/technologies/ethernetip/
Now for example, we want to read 3 values from the Modbus RTU slave and map them across to the EtherNet/IP gateway module so that it can be read by the external Allen-Bradley PLC using EtherNet/IP protocol.
Power Meter
Modbus RTU
Slave Node 1 RevPi
EtherNet/IP Gateway
Adapter / Slave
Description Address Address
Power HR40001 DATA_OUT.WORD[0]
Current HR40002 DATA_OUT.WORD[1]
Frequency HR40003 DATA_OUT.WORD[2]
Do you have any information on how to map data addressing between on-board Modbus RTU RS485 port and the Ethernet/IP gateway? (or other gateway such as PROFINET).
---
EtherNet/IP is the protocol supported by Allen-Bradley PLC’s and also some other PLC manufacturers, it is not the standard TCP/IP protocol supported by standard Ethernet ports and regular devices. From what I can tell the onboard Ethernet ports on the RevPi support EtherNet/IP protocol.
We need to read data from the Modbus RTU slave into the RevPi acting as Modbus RTU master. Then we need to read data from the RevPi which is acting as EtherNet/IP Adapter (slave) into the external PLC which is acting as EtherNet/IP Scanner (master).
Some more info here about difference between EtherNet/IP and regular TCP/IP communications
https://www.rtautomation.com/technologies/ethernetip/
Now for example, we want to read 3 values from the Modbus RTU slave and map them across to the EtherNet/IP gateway module so that it can be read by the external Allen-Bradley PLC using EtherNet/IP protocol.
Power Meter
Modbus RTU
Slave Node 1 RevPi
EtherNet/IP Gateway
Adapter / Slave
Description Address Address
Power HR40001 DATA_OUT.WORD[0]
Current HR40002 DATA_OUT.WORD[1]
Frequency HR40003 DATA_OUT.WORD[2]