Problem reading negative value modbusrtu?

[Martinus]

Hello,

I think i found a problem when i'm trying to read a negative value.

When my servodrive is running clockwise the value is positive and there is problem
But when my servodrive is running counter clockwise i get a error.

For error see attachment

How can i solve this?

Greets

Martinus

[Archie]

With it stopped at this line can you hover the cursor over "rawdata" to see what the values are.

[Archie]

I see where the problem is. Modify the code like this:

Code: [Select]

                    '* Ensure there is enought data to process
                    If rawData.Count >= (startByte + ResultingValuesIndex * BytesPerElement + BytesPerElement) Then
                        For i = 0 To BytesPerElement - 1
                            If address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) < 0 AndAlso _
                               address.Address.IndexOf("L4", 0, System.StringComparison.InvariantCultureIgnoreCase) < 0 Then
                                '* Use Big Endian
                                Result += CInt(rawData(startByte + ResultingValuesIndex * BytesPerElement + i) * (2 ^ ((BytesPerElement - 1 - i) * 8)))
                            Else
                                '* Reverse the data into little endian so the .NET libaries can convert it to float
                                FloatBytes(i) = rawData(startByte + ResultingValuesIndex * BytesPerElement + i)
                            End If
                        Next
                        If address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) >= 0 Or _
                               address.Address.IndexOf("L4", 0, System.StringComparison.InvariantCultureIgnoreCase) > 0 Then
                            '* F4 address designates it is a floating point type
                            SwapBytes(FloatBytes, 0)
                            SwapBytes(FloatBytes, 2)
                            ResultingValues(ResultingValuesIndex) = CStr(BitConverter.ToSingle(FloatBytes, 0))
                        Else
                            ResultingValues(ResultingValuesIndex) = CStr(Result)
                        End If


[Martinus]

With it stopped at this line can you hover the cursor over "rawdata" to see what the values are.

Hi Archie,

I have tested the code but then al retreived values are zero "0" nothing works then anymore.


As for the raw data value;
-      rawData   Count = 4   
      (0)   255   Byte
                (1)   255   Byte
                (2)   255   Byte
                (4)   255   Byte

Hope this helps out

Greets

Martinus

[Archie]

I see where the problem is, but not completely sure how to fix it since I do not have a PLC to test the code, so try this code:

Code: [Select]

                    If rawData.Count >= (startByte + ResultingValuesIndex * BytesPerElement + BytesPerElement) Then
                        For i = 0 To BytesPerElement - 1
                            If address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) < 0 AndAlso _
                               address.Address.IndexOf("L4", 0, System.StringComparison.InvariantCultureIgnoreCase) < 0 Then
                                '* Use Big Endian
                                Result += CInt(rawData(startByte + ResultingValuesIndex * BytesPerElement + i) * (2 ^ ((BytesPerElement - 1 - i) * 8)))
                            Else
                                '* Reverse the data into little endian so the .NET libaries can convert it to float
                                FloatBytes(i) = rawData(startByte + ResultingValuesIndex * BytesPerElement + i)
                            End If
                        Next
                        If address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) >= 0  Then
                            '* F4 address designates it is a floating point type
                            SwapBytes(FloatBytes, 0)
                            SwapBytes(FloatBytes, 2)
                            ResultingValues(ResultingValuesIndex) = CStr(BitConverter.ToSingle(FloatBytes, 0))
                        ElseIf address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) >= 0 Then
                            '* Convert bytes to a long integer
                            SwapBytes(FloatBytes, 0)
                            SwapBytes(FloatBytes, 2)
                            ResultingValues(ResultingValuesIndex) = CStr(BitConverter.ToInt32(FloatBytes, 0))
                        Else

                            ResultingValues(ResultingValuesIndex) = CStr(Result)
                        End If
                    End If


[Martinus]

Hello Archie,

Sorry for the troubles but unfortunate this code is nor working either.

Al the read value turn to zero "0"


Is there anything i could do to help


greets

martinus

[Archie]

I made a mistake in the code. This should be right:

Code: [Select]

                        If address.Address.IndexOf("F4", 0, System.StringComparison.InvariantCultureIgnoreCase) >= 0  Then
                            '* F4 address designates it is a floating point type
                            SwapBytes(FloatBytes, 0)
                            SwapBytes(FloatBytes, 2)
                            ResultingValues(ResultingValuesIndex) = CStr(BitConverter.ToSingle(FloatBytes, 0))
                        ElseIf address.Address.IndexOf("L4", 0, System.StringComparison.InvariantCultureIgnoreCase) >= 0 Then
                            '* Convert bytes to a long integer
                            SwapBytes(FloatBytes, 0)
                            SwapBytes(FloatBytes, 2)
                            ResultingValues(ResultingValuesIndex) = CStr(BitConverter.ToInt32(FloatBytes, 0))
                        Else
                            ResultingValues(ResultingValuesIndex) = CStr(Result)
                        End If


[Martinus]

Hello archie,

I wil try as soon as i have time, now its sunday time for the birthday party of my son

greets

Martinus

[Martinus]

Hi Archie,

I have tried but no luck.

I have used a blank advancedhmi solution, made the changes in the code
put in a modbusrtu with a basiclabel with plcvalue l47696

The parameter which i'm reading
_n_act (actual speed of motor)

INT32       CANopen 606C:0h
INT16       Modbus 7696
R/-

greets

Martinus

[Archie]

Did you use an upper case "L"?

The address should be L47696

[Martinus]

Did you use an upper case "L"?

The address should be L47696

Hi Archie,

yes i used a capital L

[Archie]

I will have to do some testing to figure this out when I can get to a ModbusRTU device, which will be Wednesday or Thurday.

[Archie]

I tried using the latest code change posted above with an AutomationDirect Click PLC using address L416385 (INT32), which I set to -1, and it works.

[Archie]

With further testing I discovered another problem with reading Long integers. If you read more than 1 long integer that are addressed within 20 elements, the read optimizer return a 0 for all except the first.

This will be fixed in the next release.

[Martinus]

Hello archie,

Good to hear that you found a problem...or not good :-)

Do you have a idea when the next versin wil be  released?

Thanks

Martinus