Slow Modbus serial communication

[samihamid]

Hello Every One,

I connect Labview to my Delta PLC with modbus serial communication, i succeded but the problem is communication speed is very slow. i control plc with lab view. i used lab view as an HMI.

Com port light on plc blinks very slow what to do ?

can i enhance serial communication speed ? or is there any way to read and write program on labview

[LV_Pro]

Without more information it is very difficult to answer. Need more than vague "very slow". How slow is slow, how are you determining it, what is the hardware you are using, both the modbus interfaces, what you are communicating with?

[RTSLVU]

How slow is "too slow"

What model PLC?

What are its communication options?

I have used AccuEnergy Modbus devices and they could be set from 9600 to 57600 baud serial data rates. 

[samihamid]

Hi

I am using PLC DVP 32ES2

I used lab view for displaying PLC input and output staus

LAB view can read PLC input status but it cannot read plc output staus

on PLC i see serial communication light blinking very slow where it blinks very fast when i used an hmi

[samihamid]

Hi

I am using PLC DVP 32ES2

I used lab view for displaying PLC input and output status

LAB view can read PLC input status but it cannot read plc output staus

on PLC i see serial communication light blinking very slow where it blinks very fast when i used an hmi

When i connect lab view with my plc to serial communication, light on plc blinks very slowly, looks like it transmit data very slow i used baud rate 9600

[RavensFan]

Are you sure the blink rate of the light is in anyway associated with the speed?

How do you know it is transmitting slowly?

How many registers are you trying to communicate with and at what rate?  A few?  Hundreds?  Every second?  Every 1/10th of a second?

What do you mean by PLC input vs. output status?  Which register types are you using?  Are they sequential or scattered about numerically?

What LabVIEW features are you using to communicate?  I/O library tags as part of the DSC module put into your project?  One of the several Modbus libraries you can find on VIPM or built into LabVIEW?

Show some code!

[RTSLVU]

What do you mean by HMI? I mean besides "Human Machine Interface", HMI is just an industry buzzword that can mean lots of things. What is the program and how does it work? How often is this "HMI" program polling the PLC?

Could it be that the LED only blinks when it is polled, and the HMI program is polling the PLC at a very fast rate, and your LabVIEW program is polling at a much slower rate?

As for LabVIEW can read PLC input status but it cannot read plc output status. We need better explanation on what input and output status are and we need to see your LabVIEW code.