wireless communication over modbus rtu protocol

Thread Starter

abhi_gurav

Joined Apr 5, 2018
6
I want to establish wireless communication between motion controller and human machine interface(hmi) in modbus rtu protocol, how can i do this?
 

Ian Rogers

Joined Dec 12, 2012
666
Modbus RTU doesn't lend itself to wireless... You are better off with Modbus ASCII.. RTU is too time demanding..

Modbus ASCII over wireless will be much easier to implement!!
 

Ian Rogers

Joined Dec 12, 2012
666
Modbus TCP is RTU modified to run on TCP/IP... You will need a permanent wifi connection to the gateway as Modbus RTU cannot be interrupted... The quiet periods between transmissions are a specified length and any deviation drops out the connection.

What controls the motion controller ? Has the Human interface a wifi a gateway connection? or do you have to make all this happen..
 

Thread Starter

abhi_gurav

Joined Apr 5, 2018
6
Right now HMI is connected via rs485 to the motion controller(mc-4N) and i want to make it wireless. They are sending data in modbus rtu mode through this cable.
 

Ian Rogers

Joined Dec 12, 2012
666
Right!! If the HMI hasn't a web server then you cannot use RTU with TCP... RTU will not run on a wireless radio setup..
The reason Modbus ASCII was introduced is so they could go through a modem..

Answer!!! Buffer... Make a wireless Modbus RTU connection at each end..
upload_2018-4-6_15-45-37.png
The HMI can send to the RTU server then transports wirelessly to the other.. The Micro's can buffer the data to keep the timing correct and send the same data over and over unit its refreshed... RTU has a 100ms timeout so you can maintain the connection and just update the new data as it comes in..
 

Thread Starter

abhi_gurav

Joined Apr 5, 2018
6
Right!! If the HMI hasn't a web server then you cannot use RTU with TCP... RTU will not run on a wireless radio setup..
The reason Modbus ASCII was introduced is so they could go through a modem..

Answer!!! Buffer... Make a wireless Modbus RTU connection at each end..
View attachment 149895
The HMI can send to the RTU server then transports wirelessly to the other.. The Micro's can buffer the data to keep the timing correct and send the same data over and over unit its refreshed... RTU has a 100ms timeout so you can maintain the connection and just update the new data as it comes in..
Thank you so much Ian Rogers for your valuable guidance.
 
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