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Troubleshooting an Ewon Flexy's serial connection

02 Sep 2022
When connecting an Ewon with a serial port to a device like a sensor or PLC does not work properly, there are several points of failure to consider. This troubleshooting guide outlines some common problems and how to resolve them.

 

APPLICABLE PRODUCTS

  • Ewon Flexy with built-in serial port
  • Flexy with FLA 3301 serial extension card

 

ISSUE / QUESTION / SYMPTOM

  • Unable to poll data from serial device

 

 

POSSIBLE CAUSES / ANSWER

Isolating the problem

Before correcting the settings or wiring issue responsible for the problem, of course it it necessary to identify what's causing it. Testing with alternative hardware, like a spare cable or a serial device that is known to work properly, is a good way to determine if the hardware that was replaced was the source of the issue. Another good strategy is using a serial simulator on a computer, because if the data coming into the computer doesn't make sense, the Ewon won't be able to make sense of it either. This can help save time troubleshooting settings on a device that might not actually be the problem.

 

Wrong settings on Ewon or serial device

It's important that the settings on the Ewon match the settings on the serial device, including serial mode (RS-232 or RS-485), duplex mode, parity bits, and baud rate. A serial device's default settings can usually be found in the device's user manual, or they may be set in the device's configuration software.

On the Ewon, these settings can be accessed in a couple of different places. Most are available in the IO Server settings for protocols like Modbus or DF1, including baud rate, parity, stop bits, and duplex mode. The IO Servers can be found in Tags -> IO Servers -> IO Servers List. These settings are specific to an IO Server. Others, like the serial mode, are accessible in Setup -> System -> Communication -> General -> Serial Ports.

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Fig 1. Serial settings for the Modbus IO Server in Tags -> IO Servers -> IO Servers List -> Modbus

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Fig 2. Serial port communication settings in Setup -> System -> Communication -> General -> Serial Ports

On the FLA 3301 serial extension card, port S2 only supports RS-232, while port S1 is configurable to RS-232 or RS-485. This change requires a technician to remove the extension card and change the state of a group of DIP switches on the card. More information on the configuration of port S1 on the FLA 3301 is available on page 9 of the FLA 3301 installation guide linked in Additional Info below.
 

Inappropriate wiring for use case

Because multiple serial standards use DB-9 connectors and some manufacturers may use nonstandard pinouts, it's important to verify that both ends of the serial connection are wired appropriately for the devices it connects to. One good option for doing this is using a multimeter set to continuity mode to verify that there is a good connection between a pin on one end of the cable and the corresponding pin on the other end.

 

 

ADDITIONAL INFO (Optional)