1. Navigate to Tracking :: Devices :: Serial Statistics
2. Look for CD or CTS signals
• These both indicate that the target device is ready
• Typically at least one is active, though some vendors do not send either
3. Note the RX Bytes and reload the page to see if the value increments
• This indicates that data is being received from the target device
4. Note if there are a high number of CTS shift or DCD shift events
• This indicates frequent changes in these signals
• Could indicate incorrect cabling or configuration
• Review the cabling involved using the documentation for the target device to determine correct pinouts
• These articles may be helpful:
  
• Nodegrid Serial Console: Pinouts, Cables and Connectors
  
• What is the NodeGrid serial ports pinout?
  
• Devices Pinout with NodeGrid
  
5. Note if there are any Parity Error events
   
1. This indicates that the Parity may not be set correctly via Managed Devices :: Devices
   
6. If no obvious cause is found, try swapping cable and device with a working port and the port in question
   
1. Note: make sure the two ports being swapped use the same settings or are properly configured for the new target
2. If the issue stays on the port: the port needs to be tested using a loopback plug
   
3. If the issue follows the cable: the root cause is external to the Nodegrid appliance
   
1. You can isolate further by swapping on the cable or only the target device and noting which common component is not working

If any changes are made, select the specific port and click the Reset Statistics button to clear the old data.  Then refresh the page to monitor for new events and/or changes to the signaling.

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