25- IoT Masterclass, Part3: Programming a Siemens PLC to Publish/Subscribe to MQTT Topics

[@mohamadismailbasha6083]

Thanks for the effort put on these videos

[@blociot]

Thank you for your feedback 🙏

[@郑凯瑟琳]

Hi, thank you for the video, How do I make my PLC send multiple data to multiple topics at the same time?

[@blociot]

@郑凯瑟琳 thanks for watching. If you want to send multiple data at the exact same time, you need to add multiple FB instances. Otherwise, you may change the data variables and send them in a periodic way. Also, it's easier to send data in diffefent format and data types with OPC UA PubSub over MQTT instead of flat MQTT. More details on this video: kzbin.info/www/bejne/o6fbk4GtmLSSmassi=UXvoO7UXUKGIMJDp

[@antoniomanuelgarciarey1509]

Thank you for your tututorial. In OB30 do you convert int data to an array of bytes? It seems too much programming for only transmit an int. I also want to send strings, bit, char... through MQTT to a raspberry but It seems very hard to do with an array of bytes that needs the input publishMsgPayload. I think that in previous versions of MQTT library the message was strings, I have to check ti, that is easier to manage. Thanks!

[@blociot]

Thank you for watching. That's correct. The publish array is updated in OB30 in this example. You can send any data type but every digit of the number should go to one array element as its ASCII equivalent code. I really don't know why but I wish therr was an additional input in the FB to select the array data type so it would be easier to use the FB. The conversion is not hard. You can take a screenshot of 22:52. For bits, I'd suggest combining them to a byte before sending. For string, you shouldn't need any conversion. Just parse the string and fill up your array by string chars.

[@kacperkubacki2951]

Can two clients work simultaneously within one program block? I would like one client to constantly subscribe to a topic, while the other one would send information from time to time, without interrupting the subscription of the first client.

[@blociot]

@@kacperkubacki2951 absolutely. Each client block needs to have a unique ID and they can work independently.

[@kacperkubacki2951]

Should MQTT communication work on PLCSIM v16? When trying to run it I get error 16#8601 regarding TCON 😟

[@blociot]

Hi@@kacperkubacki2951 . Unfortunately, PLCSim only supports local communications. For external communications, you can use PLCSim advanced which requires a license.

[@seattledutch]

Can I use MQTT function blocks with the Logo 8.4?

[@blociot]

Do you mean connecting a S7 PLC to a LOGO over MQTT, or using MQTT in LOGO v8.4? You can certainly use MQTT in LOGO v8.4. We have a few videos on how to do it on the channel. Here is one of them: kzbin.info/www/bejne/ZpvSknqoabimn9Esi=WbXyX2nnSu3z2s7T If you need to connect a S7 PLC to a LOGO over MQTT, you need to do some data handling at the broker side because both S7 PLCs and LOGO require a topic payload in a certain format. So you can't directly publish a payload to a topic and receive it from an S7 PLC and vice versa. But with data manipulation at the broker, you can.

[@seattledutch]

@blociot Thank you, watched it but it seems publishing is limited to predefined topics, correct? I can not seen to publish a topic from a schematic.

[@blociot]

@@seattledutch There is no instruction or block in the schematic for publishing to a topic. The procedure is two topic names should be defined for publish and subscribe in the LOGO MQTT configuration. Then a memory area is dedicated for publishing and subscribing to messages. All you need to do in the schematics is to transfer the desired value to the dedicated memory are. For example VW1 or AI1. This makes it easy to work with MQTT, but I would also like to see an instruction where we can define the topic name and the use it in the schematics. Maybe Siemens will add it in the future releases...

[@seattledutch]

@@blociot Thank you! This is very helpful! Thank you for taking the time to answer my questions and your helpful videos. I’m a software developer veteran but new to PLCs and this helps a lot.

[@Bermsompochwutiya]

hello sir , plc s7-1200 how to connect wifi?

[@blociot]

@@Bermsompochwutiya hello, PLCs including s7-1200 don't have a built-on wifi. You need external wifi client modulea if you need wifi connectivity.

[@Bermsompochwutiya]

@@blociot thank you ,sir

[@andrihadianto4473]

thank you for your tutorial, after following your instruction i found error 16#8200, cant you tell how to fix this error ?

[@gussinger6939]

can I also use this method in order to send SCL Code to the CPU and run it? Let´s say I write SCL Code in an external editor and then want to test it on a real device. Is that possible?

[@blociot]

Short answer is not directly. But TIA Portal has a feature called Openness which let you do many tasks by scripting. It might be helpful to look at. You can send your data (an SCL code in your case) to the PLC, but therr should be another interface to receive the data and save it as a FB, FC, etc.

[@akhtarshamim2424]

Thanks Sir

[@blociot]

Thank you for watching 🙌

[@AungKyawNyein-qm7jd]

I am getting "Bad socket read/write on client PLC: Invalid arguments provided." message.

[@blociot]

Are you trying to publish the data or subscribe to a topic? Do youbget this message during the complie or when triggering the LMQTT block?

[@AungKyawNyein-qm7jd]

I just make the 'EN' TRUE and it gives me the error code '8730'. I change 'keepAlive' from '0' to '10' and it give no error. I can subscribe the topic. But, 'publishMsgPayload' does not work, it carry no value. @@blociot

[@AungKyawNyein-qm7jd]

It is now working. It is needed to define 'publishMsgLen'.

[@Subscribernuern]

can you make a video about the new function in Tia Portal V18 Symbolic Access @Runtime in connection with MQTT Client

[@blociot]

Sure! What are you trying to do exactly with that feature?

[@Subscribernuern]

I want to write and read the PLC variables with MQTT and the Symbolicaccess@Runtime via a KPI

[@Plermpel]

I want my PLC to subscribe to about 200 topics, what would be the best way to ralize that?

[@blociot]

You can easily do it by changing the tags containing the topics name in a loop or in a sequence. Are they all in the same broker?

[@elkechebourabir5241]

Please sir , i followed the same steps as you but when i enable the block. An 16#8061 error appears i tried so hard but i can't fix please help me

[@blociot]

8061 is most likely because your PLC cannot find the MQTT broker. Are you using a local MQTT broker or a cloud version? You need to make sure DNS is set up correctly if not using the IP address for the broker. Also, make sure you can ping both PLC and broker on the same network.