Trying to communicate with MAGPOWR Cygnus with Controllogix

[randy741985]

To add to my previous response, a 16-bit hex value will have four digits ranging between 0-F. You should never have more than four digits in a 16-bit hex number.

Keith

Ok but if writing directly to the Hex input parameter what would be the Value be?

 

[kamenges]

I don't understand your question. Are you asking how to write a new value to a parameter in the Cygnus?

Keith

 

[randy741985]

I have it reading the correct parameters Values , I.E. from the 86 parameter directly entering 5600 hex. Problem is I get a error back when trying to read the 548 Parameter, It doesn't like the 224 Hex Value being either 0224 or 2240. also the error comes back looks like this Web_Tension:I.Data[1]16#01f0. It should be equal to parameter you are reading.

Thanks

 

[kamenges]

Not 2240. That is 4022 hex which is WELL above the Cygnus address space.
Use 2402.

The parameter ID field in the return (input) message will contain an error code if there is an error in the request. In your case the error code is F001 (after byte swapping). According to the manual, this is an invalid address.

Keith

 

[kamenges]

Remember, you are swapping bytes (of hex number pairs) not shifting and padding with zeros. In the case of 0224, the digit pairs are 02 and 24 with 02 being first. If we swap the order of the pairs we get 24 and 02, or 2402. This is why it makes things much easier to do in hex. We can work with pairs of digits and swap them as opposed to trying to do this in decimal.

Keith

 

[randy741985]

Remember, you are swapping bytes (of hex number pairs) not shifting and padding with zeros. In the case of 0224, the digit pairs are 02 and 24 with 02 being first. If we swap the order of the pairs we get 24 and 02, or 2402. This is why it makes things much easier to do in hex. We can work with pairs of digits and swap them as opposed to trying to do this in decimal.

Keith

I have been writing directly to the output data in hex. Didn't consider the Byte swap while writing direct, I think I'm understanding it 2402 did come back as good no errors. Will try this when running right now the value is Zero.

Thanks will let you know how it goes.

 

[kamenges]

Try and read parameter 511. It will be a non-zero value and should be something you can confirm. it would be a good test in the higher reaches of the address space.

Keith

 

[randy741985]

Try and read parameter 511. It will be a non-zero value and should be something you can confirm. it would be a good test in the higher reaches of the address space.

Keith

Yea I entered ff01 direct got back real value of 440.0 I will have to go look but I'm pretty sure that is right.

Thanks

 

[kamenges]

Very good. Looks like you're on it.

If you end up looking for other parameters make sure you note the data type. The response ends up in different address locations depending on data type.

Keith

 

[randy741985]

Very good. Looks like you're on it.

If you end up looking for other parameters make sure you note the data type. The response ends up in different address locations depending on data type.

Keith

Appreciate all the help Keith it is working and I got a lesson on communication with hex. I can put it in trending now.

Thanks again.

 

[kamenges]

Glad to hear it is working.

The big takeaway is endian type. It is always a possible issue when communicating between different processors. We wouldn't have had to do anything in hex if the Cygnus operated on the little endian data format of the ControlLogix operated on big endian. Also, we could have done the byte swap on the address using plc instructions like we did with the data but I thought that would add another layer to this that we didn't need to deal with at the time.

Keith