Anyone here a Serial Guru?

[CroCop]

I've got a Mark III Flow Meter.
RS485, & I can connect over a USB to RS485 convertor.
I have a RS232 to RS485 convertor, & get no joy from it.
Baud rate is set correctly, wired properly, etc., & I'm scratching my head.

 

[Ken Roach]

Rule #1 of RS-485 is that no two manufacturers designate Data A and Data B the same, so always try swapping data conductors.

The USB device probably allows the software application to command Transmit and Receive modes directly. The RS-232 / RS-485 converter requires handshaking or timing settings to switch from Transmit to Receive.

Do you have RTS and CTS connected on the RS-232 side, or just Rx, Tx, and GND ?

 

[iant]

A standard RS232 Db9 socket supplies a 5Vdc Rail
Your Usb lead may not supply that voltage to the rs5484 converter.
If you have a breakout box you could see exactly what is happening.

 

[CroCop]

Rule #1 of RS-485 is that no two manufacturers designate Data A and Data B the same, so always try swapping data conductors.

The USB device probably allows the software application to command Transmit and Receive modes directly. The RS-232 / RS-485 converter requires handshaking or timing settings to switch from Transmit to Receive.

Do you have RTS and CTS connected on the RS-232 side, or just Rx, Tx, and GND ?

I have RTS & CTS connected on the 232 side, & have already tried Data A & Data B swap.

I'm thinking the USB device does something interesting. The Emerson product I'm connecting to requires a Modem connection through the port assigned to it. First time I've ever had to do that with a Serial Port.