how to connect RS485(DB9) to RS485(15 pins) ?

[Nok]

Hi..
I want to communicate via RS485 card (8 ports, DB9). But my application using RS485 15 pins. So, I have to make the adpter connection as following

Board PC (NI-485 card DB9)

Tx+ Tx+ (pin8)
Tx- Tx- (pin9)

Rx+ Rx+ (pin4)
Rx- Rx- (pin5)

(CTS+ -- RTS+)
(CTS- -- RTS-)

No Handshaking !!!

To write command to set LED at the board is success.

But to read the data back is fail !!!!!!!

My question is How about the Gd pin of DB9 (PC) have to connect to Gnd of application board or not ?


Thanks for any kind help.

[Chris_Rake]

Since RS-485 devices can have unique pinouts you will need to consult your device's user manual to determine what the pin numbers are.

You do need to connect GND, and if your devices do not share a common ground (or one or both serial ports are isolated) you will probably have problems if this is unconnected.