PCMCIA-RS485/2 connected to RS422

[AGV]

I want to connect PCMCIA-RS485 (DB9) with a RS-422 board (DB25) in other computer. Which connectors and cable I need?

[Chris_Rake]

You will need to determine the pinout of the other board, and then connect TX+ to RX+, TX- to RX-, etc. This may require a custom cable.

[AGV]

I have built a 4-wire cable
TX+ -> RX+
RX+ -> TX+
TX- -> RX-
RX- -> TX-
I send a frame from the RS-422 board but receive nothing in the NI RS-485.
I only want to see the bytes belonging to that frame using a simple tool like TALBreakOut.
Is necessary to perform some configuration in the board?

[AGV]

How can I configure PCMCIA RS-485/2 to work with the RS-422 protocol?

If I need a clock signal, which pin is used as clock?

[Chris_Rake]

RS-485 will work with RS-422 without any changes as the voltage levels are essentially the same. However this is an async port (driven by a UART), so no clock is available.

[AGV]

OK, I must work in ASYNC mode.
So, I have configured both boards in ASYNC mode with the following parameters
Bits per second = 9600
Data bits = 8
Parity = None
Stop Bits = 1
Flow Control = None

Then, I send a frame of 1 byte but receive a different value in 2 bytes (the second is 00):

SENT ----- RECEIVED

3 ----- 7E00
4 ----- 1F00
5 ----- 7D00


Do you guess what can be the problem?

[Chris_Rake]

Are you using the PCMCIA-485 as a sync serial port? Or is this a VISA setting?

[AGV]

I think that as a sync serial port because I only configure the following:
- Device Manager > Ports(COM & LPT)
- Double click the Port
- Port Settings: 9600 / 8 / None / 1 /None
- Advanced: Transceiver Mode -> 4 wire

[AGV]

Does the PCMCIA-485 uses NRZ encoding?

[Chris_Rake]

The PCMCIA-485 is a UART-based device. The data frame is identical to that of a built-in RS-232 port, the only difference being the transceivers and voltage levels.