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Topic: RS485 TCP/IP question (Read 314 times) previous topic - next topic

lucymamaxx

Hi Everyone,

Many thanks in advance for your attention to my questions.

We have a oven has a CALogix PLC systems, the base unit (the power to all modules)of which has a RS485 port for linking to a computer (master or client of Modbus RTU) to send out instructions and receiving thermal log data from 4 individual thermal couples. The PLC is using Modbus RTU protocol to link together to the final input/output port. My plan is instead of using a computer, to use a Arduino Nano 33 IoT as the client or master to retrieve thermal logging data from those thermal couples (however, still not sure how the thermal log is sequenced in the holding register, need to find out when reading them). And then to send the log to a web server MySQL database via WiFi.

The RS485 for PLC is full duplex. And the RS485 has power supplied from base unit already.

Could you kindly recommend a RS485 shield would fit for my application please? And could you also share a sketch how to wire the RS485 shield with Arduino Nano 33 IoT please?

Many thanks in advance.

lucymamaxx

Sorry, Wrong topic, it is really a Modbus RTU question!

lucymamaxx

Sorry, wrong question again. I don't need a separate shield. just need to figure out how to connect RS485 port to Arduino Nano 33 IoT.

Paul_KD7HB

You wrote "The RS485 for PLC is full duplex. And the RS485 has power supplied from base unit already.".

How many wires does your RS485 have?

Paul

lucymamaxx

Hi Paul,

Thank you so much for your kind reply. Sorry about asking all the wrong questions again. Now I am much certain what I am trying to achieve. Here is my actual questions:

We have a oven system that has a Modbus RTU master (the HMI computer) and four RTU slaves that reads thermal couples. I am trying to read the thermal couple readings via WiFi from the RTU master.

My current thought is to create another Modbus IP network, to use a Arduino Nano 33 IoT as a master and use the RTU master as the slave of this new IP network. And try to read the thermal couple readings presumably stored in the holding register and upload them to a network database.

Is this possible? And am I right that I don't need an extra RS485 on Arduino? Is there any other devices that I need to make this possible?

Many thanks in advance for your kind help.

Lucy

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