Red Lion DSP to Modbus RTU comms issue

[Andy6]

Hi all,

I have a Red Lion Display Station Plus that I am using to do protocol conversion from a EIP Micrologix 1400 to an air handling unit that has a Carel controller.

I seem to have the communication between the DSP and the Micrologix working just fine. (Watch table shows updated PLC values) but when it comes to the Modbus side, I seem to be stuck.

Both send and receive LEDs on the 485 port are illuminated regularly (send flashing, then receive flashing right after) but attempting to get any data from any Modbus address only results in zeros on the watch table. Could it be I have the wrong Modbus addresses? If communication was not working, wouldn't any Modbus address show up as N/A?

I have attached the set up I have loaded to the DSP. The tags in there have just been for testing.

 

[JHarbin]

Hi all,

I have a Red Lion Display Station Plus that I am using to do protocol conversion from a EIP Micrologix 1400 to an air handling unit that has a Carel controller.

I seem to have the communication between the DSP and the Micrologix working just fine. (Watch table shows updated PLC values) but when it comes to the Modbus side, I seem to be stuck.

Both send and receive LEDs on the 485 port are illuminated regularly (send flashing, then receive flashing right after) but attempting to get any data from any Modbus address only results in zeros on the watch table. Could it be I have the wrong Modbus addresses? If communication was not working, wouldn't any Modbus address show up as N/A?

I have attached the set up I have loaded to the DSP. The tags in there have just been for testing.

For pulling the data from the Modbus device, get rid of the gateway block and just create a tag making the source AHU2 with the appropriate register.

I'm not clear what you are trying to accomplish, so it may be more complicated than this, but many people seem to think a gateway block is needed where it isn't. If it is needed, you would do it a different way.

 

[Andy6]

I am trying to send 2 integer values (One temperature setpoint, one damper position setpoint) from the Micrologix through to Modbus. I've tried writing to the addresses I believe are correct in the Carel controller, but have not seen any action and cannot get into the Carel to verify anything.

I just tried addressing the tags directly to AHU2 and in the watch table they come up with N/A.

 

[JHarbin]

I am trying to send 2 integer values (One temperature setpoint, one damper position setpoint) from the Micrologix through to Modbus. I've tried writing to the addresses I believe are correct in the Carel controller, but have not seen any action and cannot get into the Carel to verify anything.

I just tried addressing the tags directly to AHU2 and in the watch table they come up with N/A.

You don't have any tags created that are reading from the Micrologix.

Once you get that created, something will need to initiate the write to the AHU2. It might work the way you have it if Tag2 actually had some data in it, but it is Zero.

Try changing Tag2 to General instead of Internal and set a value that is appropriate for the AHU register. See if that will write to the AHU.

 

[JHarbin]

You don't have any tags created that are reading from the Micrologix.

Once you get that created, something will need to initiate the write to the AHU2. It might work the way you have it if Tag2 actually had some data in it, but it is Zero.

Try changing Tag2 to General instead of Internal and set a value that is appropriate for the AHU register. See if that will write to the AHU.

I mean based on your original configuration.

However, I doubt that the register you list is correct. If it is, it is the very last register that is typically available in any Modbus device.

 

[Andy6]

The file I attached previously was just for testing. I tried the last Modbus address to see if it would also return a 0 in the watch table.

Here is the actual file I'm working with.

 

[JHarbin]

The file I attached previously was just for testing. I tried the last Modbus address to see if it would also return a 0 in the watch table.

Here is the actual file I'm working with.

A bad register will return N/A

 

[JHarbin]

The file I attached previously was just for testing. I tried the last Modbus address to see if it would also return a 0 in the watch table.

Here is the actual file I'm working with.

I only have a few more minutes. What is the model number of the AHU device? You might want to try to reverse the Direction (make the two green ones Red and the Red one Green)

 

[Andy6]

It's some odd Carel PC0 controller Ive never worked with before. Italian made, and pretty light on the English manuals.

I did find one that has some mention of addresses, I tried some of those as well.

I have tried reversing the commands.

Thanks for the input.

 

[Andy6]

And I only actually need the 2 "green" ones. The red one is just to see if I can get any comms working. I assumed that if a read worked, the writes would work.