- 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.
Fig 1. Serial settings for the Modbus IO Server in Tags -> IO Servers -> IO Servers List -> Modbus
Fig 2. Serial port communication settings in Setup -> System -> Communication -> General -> Serial Ports
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)