I can't read from start byte register to n byte register from mod bus library. just cane read only 1st byte register

[waseda]

Hello everyone

I’ve used modbus library (ni modbus121). I’ve some problems. I set to read data from 0-4 byte register as fig. ni_modbus01. But Labview only show just one 1^st byte register as fig ni_modbus_02. 

I've tested by modbus poll from 0-10 byte register as fig. ni_modbus03. it can show all.

Please suggest me how to readdata from 0-4 byte register for modbus library.

Thanks

Waa

[CsabaF]

Hi,

I am not sure if this helps, but once I had similar problems. Some manufacturers use the register address (starts at 0) in their documentation, while others use the register number (starts at 1). Try to increase or decrease your register address, it might help.

More information about this here.

[waseda]

Thanks, CsabaF

It still have same error. it just show 1st register byte.

the data register :

address 0 = 22

address 0 = 24

I think adress is the same as starting with 0.

because if i set..

starting address : 0

quantity : 4

it show-> temp value only = 22

if i set..

starting address : 1

quantity : 4

it show-> temp value only = 24

please suggest me again 

waa

[waseda]

sorry, my wrong as above reply,

my correction is

address 0 : 22

address 1 : 24

[smithd]

You should check to see if you're generating any errors on that modbus request function. 

If you aren't, you might try out this library:

https://decibel.ni.com/content/docs/DOC-30140

(its also included in LV 2014 as part of the RT or DSC modules)

There is an example on the master palette which should do exactly what your tool does (pic 3).

If both libraries show the same behavior I'm not sure whats going on.