Reading on RS485 device using RJ45 port

Hello team,

I am trying to read value on a device which supports RS485 protocol via TJ45 port.
I am using ewon flexy 205 with FLA3301 extension card
I wired serial cable to the S1 port of the FLA3301.
Then I wired :

  • Transmit D- (pin 1) & Receive D- (pin6) of the serial cable to the Transmit D- & Receive D-(White/Blue & Brown) of the RJ45 cable
  • Transmit D+ (pin 2) & Receive D+ (pin7) of the serial cable to the transmit D+ & Receive D+ (White/Brown & Green) of the RJ45 cable

I am able to read via RS485 with other brand of gateway so I am sure my device is working.

Unfortunetaly I get my tags in errors

Hi Arthur,

Have the DIP switches on the serial card been configured so that port S1 is in RS485 mode? You can see how to do this in the FLA 3301 installation guide.

Did you test the same cable with the other gateway to rule out any issues with cable wiring?

If you navigate to Setup → System → Main → Diagnosis → Debug, you can enable debug logging for the device’s serial ports. That will record serial data to the realtime logs, which you can access under Diagnostic → Logs → Realtime Logs. Can you check on what kind of data, if any, is coming into the device?

Hi Hugh,

Yes I have set the DIP switch as shown on the picture.

the other gateway doesn’t use serial port but only simple connector so I use another cable to wire the RJ45 cable
Rx+ = Brown
Rx- = Green
Tx+ = White/Blue
Tx- = White/Brown

So by analogy I wire as follow
serial port pin 1 → Tx- = White/Brown
serial port pin 2 → Tx+ = White/Blue
serial port pin 6 → Rx- = Green
serial port pin 7 → Rx+ = Brown

I enabled debug on serial port 1 but nothing appears on realtime log for serial

Can you verify that the Ewon’s serial port settings match your device? You can check these under Setup → System → Communication → General → Serial Ports.

I’m a little unclear on how your cable is wired. Transmit on one side should go to receive on the other and vice versa. Is that how your cable is wired? If nothing is being logged it sounds like you might be trying to receive on pins that are also receiving on the device side.

See below the port settings

Actually I changed the wiring to the following and its now working :

  • serial port pin 3 (A+) = Tx+ (white/blue) / Rx+ (brown) of RJ45 cable
  • serial port pin 8 (B-) = Tx- (white/brown) / Rx- (green) of RJ45 cable

Thanks for your support.


Thanks for the update!