Hi! Please sign in Home >  Support > Technical FAQs

Technical FAQs
Question When I try to connect a Moxa MGate MB3180 to my serial device via 2-wire RS-485, it doesn’t work. I’ve confirmed the PIN connections are correct. What should I do next?
Question Type Installation
Updated 9/5/2017 6:01:22 PM
Hits 1
Products NPort S8000 Series,MGate? EIP3000 Series,NPort Express DE-211,NPort Express DE-311,NPort 5210/NPort 5230/NPort 5232 Series,NPort 5410/NPort 5430/NPort 5450 Series,NPort 5610-8-DT/NPort 5650-8-DT Series,NPort 5650 Series,NPort 5610/NPort 5630 Series,MGate MB3180/MGate MB3280/MGate MB3480,MGate MB3170/MGate MB3270 Series,NPort 5110A/NPort 5130A/NPort 5150A Series,NPort 5110/NPort 5130/NPort 5150 Series,NPort 5210A/NPort 5230A/NPort 5250A Series,MGate EIP3170/MGate EIP3270 Series,NPort 5610-8-DTL/NPort 5650-8-DTL Series,NPort P5150A Series,MGate 4101-MB-PBS Series,NPort 5150AI-M12/NPort 5250AI-M12/NPort 5450AI-M12 Series,MGate 5101-PBM-MN Series,MGate 5102-PBM-PN Series,MGate 5105-MB-EIP Series


To connect a serial device to a Moxa device with 2-wire RS-485, there are a few things that should be checked:

1. PIN assignment of Moxa device and the serial device. Moxa defines signal B as positive, and signal A as negative. Furthermore, the signal B will be PIN 3, and signal A is PIN 4 for Moxa devices with DB9 connectors.

2. Connect positive (B) pin of the Moxa Device to the positive (B) pin of the serial device, negative (A) pin of the Moxa Device to the negative (A) pin of the serial device.


 3. For Moxa devices that come with configuration software like drivers or firmware configuration, please check and make sure that the interface setting is set to RS-485 2w mode.

If you check the three factors listed above and the communication still doesn’t work, please check if your serial device is on the list below. We have found that there are some manufacturers that use a different definition than Moxa does, please swap the PIN connection to connect positive (B) pin to the negative (A) pin and try communicating again.
Below equipment is the list Moxa already know you should swap the PIN connection:
1. Lufft Smart Weather Sensor: WS501-UMB
2. Maxim MAX483 transceiver
3. Hawk USB Modem for communication with Hawk Sultan.
Related Questions
Provide Feedback
Quality of this article
Poor                Excellent