S71200 and king pigeon modbus/tcp RTD communication

According to the manual, the error "16#80C8" is due to the server response time being exhausted. of the "MB_CLIENT" instruction does not receive a response with the originally transferred transaction ID (see static tag MB_TRANSACTION_ID) within the defined period, this error code is issued. Well i'm not very expert in modbus communications yet, i'm really a beginner and i'm trying to get the temperature data stored in the RTD module to the PLC. in this firts attempt i am using MB_Client (MODBUS_TCP Library -> MB_CLIENT) i don't know if for what i am needing i should use MB_Client or MB_Server.

Pleaseee help me ! 

Hello.

I a little bit don't undestand why you use MB_SERVER and MB_CLIENT blocks in same time if your PLC need to be master use MB_CLIENT, if you need to be slave use MB_SERVER.

You need use only one block: master or slave

This video show how to do modbus master link HERE

This video show how to do modbus slave link HERE

danw

The King Pidgeon M340 RTD module is a Modbus TCP server that appears to require a Modbus Slave ID number, normally no longer used by Modbus/TCP, but required for Modbus RTU operation, as stated on page 12 of the manual at the link below:

https://images-na.ssl-images-amazon.com/images/I/B1zvJtpC2QS.pdf

The m340 module also has a Modbus RTU master capability using the RS-485 port to read external slave devices.  Although it implements Modbus write commands, it isn't clear if it can be used as a master to write RTD temp values to an RTU slave.  It appears that the RTU master maps the values it reads to the same register set that the Modbus TCP server uses.  I would avoid using the Modbus RTU master until communications over Modbus TCP is established and working.  The RTU Master register map on page 19 makes no sense: the hexadecimal button is clicked but the map's registers are clearly numbered in decimal base 10.

Page 21 shows the register map for the Modbus TCP server registers.  Note that the registers are (3)xxxx Input registers read with Modbus Function code 04, not (4)xxxx Holding registers read with Modbus Function Code 03.

I suspect that registers (3)0000 through (3)0007 labeled as AINxRTDx are raw values, maybe even A/D counts, whereas (3)0008 through (3)0015 are temperature values in Deg C, with the whatever calibration offset value is added or subtracted.

The PLC will have to be a Modbus/TCP client to talk to the RTD server box.
 

Note: The manual you referenced has already been updated: ​

"https://www.iot-solution.com/u_file/2012/file/662ef0da4d.pdf"

I'm still investigating, i think my ignorance is in the configuration of the ports, at least i don't know which is the port of the modbus slave for the s7-1200. I have configured the RTD module as default modbus port "502"

I'm Everything you have written has helped me to scan the modbus communication with a software. Now i can read the registers with "CAS modbus scanner" software. Although i have not yet managed to configure the MB_Client blocks in tia portal to be able to read those registers.

I think i've made some progress on this topic. I have created a routine in the main block of the S7-1200 PLC (Tia portal V17, CPU 1212c dc dc Firmware V4.5) I have used the MB_Client instruction (Instructions -> Communications -> Others -> MODBUS TCP "v6.0" -> MB_Client). I have created 2 datablocks with the optimized block acces option unchecked, in 1 db i use the "TCON_IP_v4" function to configure the address of the RTD modbus Server analog module. In the 2 DB i use an array (Array[0..15] of word) to receive data from the module registers. I found in the King pigeon module  manual that addresses 30001 = 16 bit int : RTD1 ADC Value, Read Only.

Note: Now i see that there is communication between PLC and King Pigeon RTD module. But reading of records in PTR is not being stored ! i'm going to attach a screenshot i know i'm close and with the help of the experts on this site we can achieve it !.

Please help me I know we are about to achieve it!

danw

I'm a Modbus guy, not a Siemens PLC guy, so I can't help you with the Siemens programming.

I would suggest that you read (3)0009 - (3)0016 and get the scaled temperature values rather than A/D counts in (3)0001 - (3)0008, but if you want to make more work for yourself interpreting A/D counts, go for it.
 

 I'm very happy ! With the help and contribution of each one of those who have participated in this post, i have managed to carry out the communication successfully and with the reading of the registers that i needed to read. I love you all. May this site continue to grow   !