How to Write Multiple Register Inputs

[mesutonus]

Hi,

I am working on to control a device over modbus.  Reading is ok but i can not write multiple register inputs.

Device sends hex data as  short[]  array.   While writing, i did the same but i got exception  overflow.. 

I attached the spec page of the fuction.

Values should be :

Vega serial address  : 1
Sub Function code : 2 (0x02)
Meter addressed :  1
Product addressed : 1  ( 0x31)
Sub function code :  2 ( 0x02)
Preset :  95.5  ( any double value)
Max Weight :  100 ( any double value)
Reserved : 0 (0x00)

How can i populate this message?   I am trying for days. Already read all forums, blogs, everything..

Could anyone please help??



 

[Archie]

Function code 2 is a read function. It is not possible to write. Below is a list of typical Modbus function codes, if you notice there is no write or force function for "Inputs"

01 Read Coil Status
02 Read Input Status
03 Read Holding Registers
04 Read Input Registers
05 Force Single Coil
06 Preset Single Register
07 Read Exception Status
15 (0F Hex) Force Multiple Coils
16 (10 Hex) Preset Multiple Regs

[mesutonus]

Sorry, written by mistake.

Function Code  : 16
Sub Function  Code : 2



modbusRTUCom1.Write("40001", datapack);  is what i do..

[Archie]

Is your datapack and array of string values?

Dim datapack(2) as string
datapack(0)=10
datapack(1)=20
datapack(0)=30

[mesutonus]

When i read from device it returns  16 bit int array. I convert it to 32 bit, then to hex. After combining hex parts together i convert it to ulong number, then byte and then to double.   
So i think it expects   hex values in short format when i send.

I tried

data[0] = "hex val"
data[0]  = "Int16 val"
data[0] = "UInt16 val"
data[0] = "byte val"
...
..
all of possible combinations i know..

[Archie]

Your string values have to be strictly numbers:

data[0]="123"

[mesutonus]

Ok but in which format?  Like

double doubleval =  75.5;

data =    Convert.ToUInt16(doubleval).toString()  ??

or its bytes? What about crc values? Will they be calculated by short values and then converted to string before sending or calculated on string vals?

May i ask if you can give a example for me for attached mapping?

[Archie]

Dim data(3) as string
data(0)="111"
data(1)="222"
data(2)="333"
modbusRTUCom1.Write("40001",data)

[mesutonus]

Does component convert "111" to ushort when sending?

[Archie]

Does component convert "111" to ushort when sending?

Yes, it converts it to a Uint16

[mesutonus]

But device returns signed int16 while reading registers?

[Archie]

I'm sorry... I meant that it does convert to an Int16

[mesutonus]

Spec says ;

Coding System :  8 Binary bit hexadecimal 0...9,A....F.    Two hexadecimal char in each of 8 bit field of message.

[Archie]

What spec?

[mesutonus]

Spec document of the device.