About RS-485 port controlling?(one way or two way)

J.Y.

Dear all,
I try to control a I/O sensing device called ADAM-4051
I must send command to 4051 via RS-485
But , the response is back via same RS-485 cord, too
How can I connect the pin between 4051(only D+ and D-) and AMX?
Thanks a lot.

Chip Moody

JY, you didn't mention which AMX controller (or expansion box) you're trying to use, but if you look in the manual for it you should find pinouts for the RS232/422/485 ports. On a current NI-series controller, you would be connecting pins 1 and 9 together and using them both as connection "A", pins 4 and 6 togther and using them as "B", and pin 5 for ground. Since the manual for your device is using different designations for the RS485 signals you might have to try reversing the connection, but start out connecting "A" (pins 1 & 9) from the AMX to "D-" on the 4051, and "B" (pins 4 and 6) from the AMX to "D+" on the 4051. If the 4051 doesn't have a ground connection on the 485 port, you can probably get away without connecting pin 5 on the AMX to anything.

In your code, make sure you use the right SEND_COMMAND to turn on RS485 on the port you're using. After that, you send and receive strings the same as you would with an RS232 device.

- Chip

J.Y.

Chip,
thanks for your reply.
I connected pin 1 & 4 together
and pin 6 & 9 together ,
Am I right?
I send_command 4051,'set baud 9600,n,8,1 485 enable' on data_event's online
when I send_string to 4051
It works fail.

NMarkRoberts

J.Y. wrote:

I send_command 4051,'set baud 9600,n,8,1 485 enable' on data_event's online when I send_string to 4051 It works fail.

I don't know if this matters, but the syntax I always use is

'set baud 9600,n,8,1,485 enable'

note the additional comma.

Mind you, I've managed to avoid enabling 485 so far, so I may have the syntax wrong.

Marc Scheibein

J.Y. wrote:

Chip,
thanks for your reply.
I connected pin 1 & 4 together
and pin 6 & 9 together ,
Am I right?
I send_command 4051,'set baud 9600,n,8,1 485 enable' on data_event's online
when I send_string to 4051
It works fail.

small mistake....

connect pins 1-9 and 4-6