Which is better between Modbus RTU and Modbus TCP?

Choosing Modbus RTU or TCP is like choosing a conductor for a band, it depends on the size of the band and how you want to perform. Let's not look at complex parameters, just talk in human language and talk about how it feels to actually use it.Simply put, They're not even the same“speak”way.

RTU: like a“Master slave”The old-fashioned yamen.

• How does it work: There must be one in the system“master” (For example, the mainPLC) , All other devices are“Slave” (For example, robots) . Master, ask one, I'll answer one. Master doesn't ask, I must never speak up voluntarily. Having one more master is not enough, It will be messy.
• What wire should be used: Usually, shielded twisted pair cables with two cores are used (RS-485）, can“Hand in Hand”Connect a string of devices (Up to thirty at most) , The distance can reach over a thousand meters, Anti interference is also good, Suitable for situations where all equipment is concentrated in the workshop.
• Where is the trouble: It's a bit troublesome to configure. master (PLC) And all the servants (Robotof Many.“speaking speed” (Baud rate) , “accent” (check digit) Must be exactly the same, One parameter is set incorrectly, The whole conversation collapsed.
• Fast or not: It's the fastest“speech rate” (For example115200Baud rate) , Convert to your familiar download speed, Approximately every second14KBMouth),Transfer point switch, Temperature data is sufficient, But I want to synchronize a bunch of complex instructions in real time, It's a bit difficult.

TCP: like a“LAN Brother”The WeChat group.

• How does it work: all equipment (Robot, computer, PLC) Plug in the switch, It's like joining the same WeChat group, Everyone has it nowIPaddress. As long as it is within a network segment, All are“Brother”, Anyone can @ others in the group if they have something to do, More flexible.
• What wire should be used: Just use a regular Ethernet cable (RJ45, usingJust plug it in.
• Where is convenient: Minimalist configuration! No need for anything“speech rate”“accent”, Just need to set a different one for each deviceIPaddress (For example192.168.1.2, 192.168.1.3…) You can make a call, almost“Plug and Play”.
• Fast or not: The speed is crushing grade. Using a 100Mbps LAN channel, Transmitting data with a whooshing sound, Can make multiple machines respond more synchronously, avoid“You asked me to play the next key, I'm still playing one”The Embarrassment.

So which one is really useful? It's up to you.“Band”What do you need. In the following situations, using Modbus RTU (“Master slave”pattern) more worry-free:

• The equipment is old and economical: Many old peoplePLC, The old instrument only has a serial port, No internet access, usingRTUIs it the only or most economical choice.
• Small and concentrated scene: Your several robotic arms are all in one cabinet or a small workshop, Close distance, There aren't many points either.
• The environment is quite noisy: Inverter in the workshop, Many large motors, High electromagnetic interference. RS-485The anti-interference ability of the line is durable and long-lasting, Relatively stable.
• Pursuing absolute stability: Master, call each name one by one, The response time is very fixed, Suitable for strict control of timing requirements.

In the following situations, choose Modbus TCP (“LAN Brother”pattern) More fragrant:

• Multiple and scattered devices: Equipment is distributed throughout the workshop, Even across floors, Build a network using Ethernet cables and switches, Bila, a long one“Hand in Hand”Convenient bus, Much more reliable.
• I want to spread it quickly and extensively: Real time synchronization of large amounts of data is required, Or perhaps in the future, it could be integrated into the visual system, Transmitting complex parameters, The high bandwidth of the network port is an absolute advantage.
• Afraid of trouble and wanting to save time: Completely unable to tolerate matching the baud rate for each device, The tedious debugging of check bits, I just want to create oneIPIt's settled.
• Thinking about expanding in the future: It is possible to add a computer for monitoring at any time in the future, Or connect to the factory management system, Internet access without any obstacles.

An excellent compromise solutionIf you only have a pile of support in your handRTUThe old equipment, But I also want to enjoy itTCPWhat about convenience and speed? Can I add one?Protocol Converter (Also known as serial port server) . Use old equipment485Connect the wire to this box, Insert the internet cable into the box again. like this, On the computer orPLCit seems, The entire string of old devices has become a beltIPNew device for address, Can be used directlyTCPTo manage. This method can save many old devices, Very practical.

The final honest statement: To save money, Be stable, The equipment is old and concentrated, chooseRTU.

To be convenient, Hurry up, To expand, Toward the Future, chooseTCP.

Combining your robot band project, If there are only a few robotic arms, Simple action, The requirement for synchronization accuracy is not abnormally high, RTUEnough and save money. But if we want the band to perform more complex songs in the future, Add more“Musician”, It is also convenient to tune and rehearse, Then go straight upTCP, In the long run, it will definitely be more fragrant.