How does Nodegrid determine the status of each Managed Device for serial connections?

How does Nodegrid determine the status of each Managed Device for serial connections?

Nodegrid appliances with RJ45 and USB serial ports will use the incoming RS232 signals to determine the status shown on the Access pages:

  • Green indicates the device is ready and no users are connected to it.
  • Grey indicates the device is not ready and no users are connected to it.
  • Blue indicates one or more users are connected to the device.

 

Changes to the RS232 signals will also trigger Nodegrid Device Up and Nodegrid Device Down events shown on Tracking :: Event List :: Events and sent via Auditing :: Events :: Device Events.

 

Since different vendors utilize RS232 signals differently, it is important to ensure each target device connected to the Nodegrid appliance is configured accurately.  Each port has two settings involved in determining its status.  Both are set by editing the port from Managed Devices :: Devices:

 

  • RS-232 signal for device state detection:
    • Has options: DCD, None, or CTS
    • Monitors the selected signal for status
  • Enable device state detection based in data flow:
    • Can be selected or unselected
    • Monitors received data (RX Bytes) for status

 

The default options are DCD for RS-232 signal for device state detection, with Enable device state detection based in data flow unselected.  To determine which options are best for a given target device, it is necessary to review what signals are present when access is working properly.  Here is how to check if access is working:

 

  1. Navigate to Access :: Table
  2. Click Console for the specific port
  3. In the new tab that opens, press Enter to see if there is a response
  4. If there is no response, troubleshoot the connection: How to troubleshoot RS232 serial connections

 

Once access is confirmed as working, navigate to Tracking :: Devices :: Serial Statistics to review the current RS232 signals for the specific port.  The active signals will determine which options should be set on that port in Managed Devices :: Devices:

 

If neither CTS nor CD is active:

  • Set RS-232 signal for device state detection to None
  • Select Enable device state detection based in data flow

If CTS is active and CD is not active:

  • Set RS-232 signal for device state detection to CTS
  • Enable device state detection based in data flow is optional

If CD active with or without CTS activity:

  • Set RS-232 signal for device state detection to DCD
  • Enable device state detection based in data flow is optional

 

Note when Hardware based Flow Control is used, this can impact activity for the RTS and CTS signals.  When either side exceeds the maximum data rate, the far side will no longer see a CTS signal.  This means when both CTS and CD signals are active, it is preferred to set RS-232 signal for device state detection to use the DCD signal.

 

To learn more about RS232 signals, please review: What do the various RS232 signals mean?


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