FMB125 & Ruptela FLS PRO fuel level sensor (RS232)

Hello guys, i have just installed FMB125 + Ruptela FLS PRO fuel level sensor and attached it to Port RS232 of the device and LL1 in the configurator, but I am not getting any reading from that port, (-4). Does FMB125 work with this particular sensor by Ruptela? Kindly advice.

Hello, Richy,
as FMB125 has RS232 interface, fuel level sensor supporting RS232 should work on this device. Before configuration make sure that all connections are done correctly: RS232 TX, RS232 RX and GND. TX of FMB125 should be connected to RX of external device and RX of FMB125 should be connected to TX of your external device. With regards to configuration, you should enable RS232 mode in RS232\RS485 tab of Teltonika Configurator. In RS232 Mode section LLS mode should be selected. Please note that RS232 baudrate selected should match the baudrate of external device. For this refer to your external device manual. After correct configuration of RS232 settings, enable I/O elements for your connected Fuel level sensor in I/O tab of Teltonika Configurator.
Best regards

Hello Jonas thanks for the response, just to be clear you mean should interchange the TX of FMB125 to and connect to the RX of the Sensor and vice versa? I had connected the FMB125 RX to the sensor RX and the TX to the sensor TX.

Yes, TX and RX should be interchanged in RS232 interface. Both communicating RS232 devices have transmitter connection TX to transmit data to the other device and receiver connection RX to receive data from the other device.
I hope this clears things out.

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Very clear now. I’ll try that and give feedback for the community’s sake.

Thanks Jonas.

Hello Jonas,

I tried this connection and configuration but i still get -4, it’s not reading. It is the FLS by Ruptela.


Please make sure that the mode, baud rate, and parity are selected correctly.


Kindly check the datasheet of the Fuel level sensor that you wanted to integrate with our device.

Best Regards,