I am struggling to obtain Modbus data from an Intesis Module that translates in/outputs from my Samsung Heat pump to Modbus RTU.

The Intesis module is connected to the LOGO CIM and CIM indicates that there is a working S7 connection between the LOGO and CIM Module. I have obtained sensible data from the Intesis using Modbus Poll and a direct RS485 connection from my laptop.

When trying to connect to the CIM using Modbus Poll and Modbus TCP (slave ID 1) I only get read errors and write errors even when the laptop IP is "whitelisted" in the CIM settings and the CIM is indicating a working Modbus connection between laptop and CIM.

When I try to get input using "Network Analog Input" using the settings attached I only get back 0 value where I should be having a number close to 200 (my room temperature in decidegrees).

I somehow only manage to upload 1 attachment in the opening post, will try to upload some more in a reply.

How do I obtain the data from my Intesis module?

Hi,

did you check if the data from your RTU is in the CIM?

If you connect to CIM via Web-browser use the RestFulAPI interface to check wether the RTU data (200) are in the CIM VW0&2. Maybe you need to an offset 1 to the register number.

https://"IP of CIM"/pi/rest/vu0

(This command in Web-browser show VW0 unsigned)

If you found you 200 there, then configure the data exchange from CIM Memory to LOGO! via the S7-data configuration table of the CIM. Then you have the RTU data in LOGO! on the configured VM-address.

Hope this helps

These are the settings I use on Modbus Poll (with on the left the values read close to 200 on line 4 and 5).

After trying this I  reconnected the CIM to the Intesis module, added another line to request with HR6 and used the following link to read some data:

https://192.168.178.11/pi/rest/vu0   and also with vu1/vu2 at the end.

Finally some data! The first attempt showed 195 as a result when using vu1 which is either my current room temperature x 10 or my room temperature setpoint x 10 (they are equal at the time of testing).

However: vu1 is showing 3 different results when refreshing a few times. The following numbers pass by:

195

50115

49920

Sometimes they stay upon refreshing, sometimes not. I do not see these numbers pass by when using modbus poll over a Modbus RTU connection directly.

Cable used from the CIM to the Intesis is 2-wire STP with a length of approximately 20cm. 

Cable used from my laptop to the Intesis is the same cable with a length of approximately 1m.

Shield is not connected to the Intesis as it does not have a shield connection. I did connect the shield to the laptop and to the CIM.

Question now is: What to think of the 3 different numbers passing by?

Hi,

if you "read" vu0 via RestfullAPI, then it is byte 0 and 1. If you get the right value when you read vu1, then it looks to me the data format may be different, or the offset of 1 is missing.

I believe you need to add the offset 1 to the HR/IR you need.

Why the value is not stable I can't answer. May it be possible that your ModbusRTU is polling several RTU devices and use the same memory range for diverent devices? 

To get the value into LOGO! configure a S7-data transfer from the CIM (VW1) to LOGO! VM-memory.

Simplest iway to show the result s to use a analog network input --> analog amplifier and show the analog amplifier on the LOGO display via text message. You can also use the online test and open the datatable with VWx.

Hope this helps

The need to apply an offset is fairly standard and easy to fix.

I do not really understand how/why the CIM could be polling for more than 1 device as it is only configured to poll for the few lines from device 1 I configured as shown on the picture.

Polling interval is set to 1 second which should be rather easy to handle for the Intesis.

Some experimenting with enabling/disabling the terminal resistor and powering both devices on/off yielded no improvement (I do get different numbers but still sometimes sensible ones and often nonsense. Converting the numbers to HEX did not get me one of the Modbus error codes either.

The P1 light is blinking at a very high frequency and I do not really understand why as the CIM is set to only poll every second....is it somehow polling much faster or could my Intesis device be sending data every few ms even though I only request data every second?

An additional test I did was to read the data using the same 20cm cable between CIM and Intesis as well as between laptop/Modbus Poll and Intesis.

On the laptop: Zero errors, only sensible data. Using the CIM...more nonsense than sense.

If I make 2 lines in the data table on the CIM requesting the same parameter:

Requesting VU0 yields 49920 as a result (conistently)

Requesting VU1 yields 195 as a result (consistently)

Requesting VU2/3/4/5... yields 0 as a result.

Modbus settings on the CIM as in the attachment.

Is this some sort of malfunction on the CIM?

I will try to get the 195 value to be read on the LOGO tomorrow...

Hi,

first I would make sure that no other device then the CIM, PC with Web browser and your ModbusRTU device is connected. This makes sure, that no other device or SW can influence the value.

2. Only configure one register of your RTU device on one memory location in CIM.

3. Find out if an offset is needed. To do so, change the HR adress -1/0/+1. Example: you need HR 3 so test with HR2, MR3 and HR4 in the RTU data table.

see pic RTU pic1

4. Check with the RestfullAPI if the value is valid and stable.

5. If the value is fine in the CIM, configure the S7 connection to LOGO! and check if the HR is right, has a valid value and can be sown on the LOGO! display or is valid in the online test data table.

Also check in the RTU device, if the needed value is realy in HR. It may also be a IR.

According to my knowledge the polling (1 sec) doesn't influence the data transfer.

Good luck.

Well this fairly straightforward plan turned out a bit different...

Followed the steps, then via RestFul Api a check on VU0 with modbus register 4 configured as the only parameter: Stable at 195. Nice.

Then changed the thermostat setpoint to 20 which should translate to 200 instead of 195: Value fixed at 195. Changed the modbus register to 5 instead of 4 (should have given 196 at that point) RestFul reads 0.

Power-cycled the CIM: Web interface started to become slow and unresponsive.

Full reset of the CIM: Web interface again responsive as new but the fixed value of 195 changed to 0 even when double-triple checking all wiring, settings, and so on.

Connected the RTU cable to my laptop: Flawless communication and nothing but logical values.

Cable back to the CIM: Only 0 as output on RestFul API.

Changing the modbus RTU register a bit back and forth between 3 and 6 (logical values of 195 (setpoint) and ~195 (measured value) should both be in range: all that gets returned is 0.

Changed the RTU cable (you never know): Everything zero.

Connected the changed cable to my laptop: Flawless communication with logical values.

Just to be sure...this is correct wiring of the CIM right? Ground at the top is connected to the casing but not to the RTU Cable shield. The casing is connected to the same ground as all 230V equipment. RTU Cable is 2-pair STP.