cRIO NI 9871 1073807298 (VISA: (Hex 0xBFFF003E) Could not perform operation because of I/O error.)

[Spaca]

Hello everyone,

I need to establish simple two wire communication between cRIO-9063 with NI 9871 (RS485) and measurement device HT100. I'm using the cRIo in "Scan interface" mode.

I send a specific message from NI 9871 and measurement device should respond with same message, which it does. I can even read the message without a problem in VI, but I keep getting an error -1073807298 (VISA: (Hex 0xBFFF003E) Could not perform operation because of I/O error from VISA read. The communication is set properly baud rate, n. of bits, no termination character, no parity, no flow control. I'm not so sure about setting of timeout, but it should not be a problem.

The error occurs even when I send wrong message and responding device does not influence communication line in any matter.

In attachment there is my project and screenshot from o-scope to show the communication (timing, voltage).

Any suggestions? Thank you in front!

[Spaca · Accepted solution]

I was missing termination resistor. Sorry for spamming.

Now it works (new o-scope screen attached).

[nico1981-2]

how many ohm have those termination resistors?

[Spaca]

Typically 120 ohms.