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Using the modbus debug port for IAP model products with error exception codes

Using the modbus debug port for IAP model products with error exception codes

Owned by Jane
Feb 10, 2020

Is there a method to check what is preventing me from polling my modbus device thru your Lantronix IAP product?

Yes,
       If you are running the Modbus Bridging firmware you can access a debug port to view data passing and look for error codes.
 
To reach this debug port you will need to use Telnet to port 3000.
Example:  From a DOS command Prompt.
 
telnet 192.168.1.116 3000
 
This will get you to the Debug screen.
Modbus Test version - DEBUG
 
If communications are passing you will see data going by like
 
Net_Req[#012] 01 00 00 00 00 06 01 03 00 00 00 0A 
Net_Rsp[#009] 01 00 00 00 00 03 01 83 0B
Net_Req[#012] 02 00 00 00 00 06 01 03 00 00 00 0A No Response!CH Err = 65521
Net_Rsp[#009] 02 00 00 00 00 03 01 83 0B
Net_Req[#012] 03 00 00 00 00 06 01 03 00 00 00 0A 
Net_Rsp[#009] 03 00 00 00 00 03 01 83 0B
 
If you are getting Err=655**   these are specific error codes found below.
 
 
Error Code Discription of Error Code
65520
Bad CRC
65521 No Response
65522 Bad form (Invalid Character)
65524
Overflow (More that 255 bytes)
66525
Incomplete Data (not everything expected is in data stream
66526 TCP/IP Bad Sequence number
 
 
Explained more:
65520 – Bad CRC
 This is a check sum error, The data coming back doesn’t match up with estimated size in the serial Modbus string.
 
65521 – No Response
  This error usually means the slave device is not responding back.  Suggest to check wiring of device, check registers you are attempting to poll or check that the TX and RX receive pins are correct.

65522 – Bad Form
   This is usually found on the Request side. This error indicates usually that the data is not the Modicon/Rockwell expected Modbus form.

 
65524 – Overflow (more then 255)
       This is a sign that the data is getting corrupted on the connection or getting noise on the line. A standard Modbus data request or response will be less then 255 characters. The data amount is in the packet so checking vs what is the request or response then checks the count of bytes.
 
65525 – Incomplete data (Not everything expected)
       Our device is interpreting that something is missing in the data stream or data is not formed correctly, this could be due to a non Modicon/Rockwell modbus format or noise on the line.
 
65526 – TCP/IP Bad Sequence number
        This error is rare, but the tcp packet sequence is not correct, or segment is not correct, which indicates there is a delay and full data may not be arriving to the Lantronix device on Modbus TCP.
 
 
 


[Originally Published On: 02/07/2019 03:15 PM]

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