How to flush Echo in VISA

[samriddh]

Hello,

I am using LabVIEW VISA functions to write and read on the serial port. I am having USB to serial drivers installed on my PC. Actually the application is to be run on RS 485 (Two Wire) Network and i having RS 232 to RS485 Devices connected to my PC. There is a physical provision in the form of connections on Converter either to use RS485 Signals or RS232 Signals. I have made some VISA Read & Write Vi's. I also have to test these with RS232 to TTL Converter because the end device is also compatible with TTL Signals.

I don't know whether the same vi's will work fine for the TTL, as i think in TTL, Only one wire is there for communication on which transmit and receive can be done.

It might produce echo after i write some data and reads afterwards for the response and can receive the echo instead of actual response..

How to discard or prevent icho to be received. Can anybody tell me the solution.

Thanks & Regards,

Samriddh Sarbalhi 

[Albert.Geven]

Please study a bit better on how rs485 works.

You surely need two wires both used at the same time for sending or receiving but sending and receiving cannot be done at the same time.

Indeed the pc can look at the lowest level (if you have built in rs485 on a card) to check if what is sent is also coming on the line.

But that should be covered by the converter. So you don't have to worry about echo's.

Another point is do you terminate both sides of the rs485 to get rid of reflections on the wires?

[samriddh]

The Network is properly terminated. You got it wrong, in place of RS232 to RS485 Converter, RS232 to TTL Converter is used now.

Thanks & Regards,

Samriddh

[GowrishBV]

Hey,  
Even I am using RS 485 Device ANALOX CO2 sensor, I have to remove echo to ger the data from the sensors, 

COnnection details are given below

Sensor Side                          cRIO side (NI 9871 4 port RS 485 Module)

A (Non Inverting Terminal)       Tx+ and Rx+

B(Inverting terminal)                Tx- and Rx-

Is this right? Is your problem solved?