Hi All,

I used a RS-485 to Ethernet gateway for receiving a power meter data. I used Mod scan software and selected Remote Telnet Server Connection and able to receive the data in my PC. My doubt is that whether it is possible to make this connection into PLC to receive the same data i receive through Mod-scan PC software. I will make it clear, it is just a gateway, not RTU to TCP converter. So whether this is possible?

Thanks,

Jay

 Hi Duris,

Thanks for the prompt response. So whether we can use Modbus client for this to receive the data because the Power meter has Modbus RTU. so to pull out that registers we need Modbus support I guess. Can you give some suggestions what to try for testing?

Just read your reply in that post of Milos and you suggested to use TCON. I will try that. So in the TCON we just give the modbus register values will work or whether there is nay particular specification for that. I am new with TCOn instruction. Anyway, i will give it a try.

Thanks,

jay

Duris_I

Hello,

probably had same piece of HW (very close) to my tests. Generally, if this Gateway is RS485 to Ethernet, some defined protocol is on Ethernet side. For standard is TCP/IP with defined port value for use. This is like now one thread from user Milos here. There are also other services what can be configured on that Gateway/s on other Port/s. You need make only tests if they are functional.

 Your understanding is right. I can only select Remote Telnet Server option in Modscan softwware and read the modbus registers using that gateway. if i select modbus TCP connection, there is no response. Maybe i am not configuring the gateway right. But i tried different options in that gateway and only this particular option works out. So now i am learning TCON to work out. I am getting an error 80C8. need to figure out how i can resolve it.

Lets see.

Jay

Duris_I

Hello,

don't know if I understand you correctly, maybe not, maybe someone gives you right answer. In my opinion your Gateway has probbaly full functionality on both sides probably, also general TCP/IP to serial adaptation. Logically, if that Gateway has on other side MB RTU protocol, I can't imagine only <general> TCP/IP protocl on other side. Some exact change of protocols must exists in this specific case. So I expect on other side of your Gateway also MB TCP selection. Look to that topic of Milos here today. This is typical example of general Gateway that only change Ethernet to Serial and vice versa of course (this is expected). This isn't specific (Modbus) system, only change simply packet to serial raw data, so what you send via f.ex. TCP/IP you have exactly on serial side of Gateway. Helpful?

Meanwhile answer: yes TCON and related next instructions/blocks TSEND/TRECV/TDISCON.

Hi All,

Just few questions about my testing.

1) I tried TCON, TRCV, instructions, but I received some characters which i get using TELNET cmd window which is not the actual data. I understand because through TElnet cmd i didn't use any addressing or anything. so it is fine.

2) I tried MODscan software with remote telnet server and with proper addressing, it can read data from the meter. So I think there is no problem in communication. 

3) then i tried MB client instruction with PLC tio see whether i can have any luck. I know i am doing something which is not right, because there is no conversion from MB RTU to MB TCP. so MB client with TCP can't work.

My question is that how can i achieve the same what Modscan software did by using the S7-1200 PLC. what instructions should I use?

Can someone give a sample program for this so that i put it in my PLC to see the function. I had attached the Data in the attachment. Please have a look and guide me. If I can make this work, it will save me sometime instead of buying any extra Modbus converters or Communication modules in the project.

and it will be a good learning for me as well.

Thanks,

Jay

 Hello Duris,

Sorry for the trouble again. I had installed the software Hercules you mentioned. Could you just guide me what should i start with. Just bit confused whether i should connect the Serial side of the gateway to my PC and Ethernet to the same and read the communication. Bit confused now about what should i do. Can you give some step by step instructions? That will be helpful.

Thanks again,

Jay

Duris_I

Hello,

yes, you need to know exactly what protocol/conversion is set on both sides. Your situation is same to Milos. Your adapter is general Serial to Ethernet in my opinion (after your picture) but your not correct info about some RTU meter correctly received data, set some doubts to me. Again, you need to know what Modscan does, this is important because it change internally protocol to Modbus RTU over TCP probably, but your adapter hasn't this function! You can check this attach on serial side PC serial monitor SW (recommend Hercules) and check incomming message. everytime you need check settings on HW/SW. In your situtaion, pls check also differencies between MB protocol versions on web. How you need implement this is in Milos topic.