My AB7702-B cannot forward

Hi everyone
Im using AB7702-B to connect and forward the signal from a CET PMC-33M-A , a Digital
Multifunction Meter , this one is using modbus RTU. The problem is i cannot poll the modbus signal to the Meter through AB7702
These followings are things i have checked:
1.All the cable is fine , the pins is connected correctly and not damaged
2.The baudrate, format , ID are correct
3.I can poll modbus from the Meter normally when connect its directly to PC through RS485 RTU - USB cable
4.The AB7702 can forward TCP modbus signal from other devices (i used netbiter IOX-DAIO) , RTU of course

Thank you for reading, do you have any idea about this problem?

Hi @PhiNguyen,

Can you please let me know the LED statuses:


Do you receive any errors from the meter?

Have you tried swapping the polarity on the RS485 connection?

Can you provide a screen shot of your configuration?

Can you possibly provide a packet capture from the TCP/IP network?

Thank you,


Hi @kyle_HMS ,thanks for your responding
1.The Status is green, the Serial Link is no signal,the Activity and Link is green
2.I dont receive any error from meter
3.Yes i tried swapping the polarity
4.My configuration


So the meter works as expected when you use a different RTU device?

What are you using for the Modbus TCP client/master? What is the address where you are sending the frames? Which function codes have you tried? Can you share the configuration or a screen shot from the master?

Yes, the meter worked fine with other RTU devices

I only used Modbus Poll to test the connection , here is the Modbus Poll settings

And the Meter settings

Can you try setting the gateway register:


And then try to read some of the gateway’s registers?

Also, can you share a screen shot of the gateway’s Status page?

Have you made any progress on this case?