NI cRIO-9871 serial communication problems

[arevh]

Hi,

I'm using NI cRIO-9871 RS485/RS422 Serial Interface Module with NI cRIO-9064 integrated controller and chassis to communice with Modbus power meter.

While testing the communication I am not able to read data from the meter. It appears there are some issues with serial communication.

To find the issue I have checked several points.

1. According to NI C Series Module Compatibility Chart cRIO-9871 is supported in FPGA and Scan mode, for all cRIO platforms. 

So there are no any compatibility issues.

2. I have tested the module with the provided example for FPGA (NI-987x Serial Loopback). While testing it was not giving any errors while writing data, but was not reading sent data.

3. I have tested the module in Scan mode with example provided for the serial communication (Simple Serial.vi). It was writing successfully, but was giving Timeout error while reading.

4. I have tried also to test data transmission with MAX Visa Test Panel. And again it was writing data without errors, but while reading it was giving Timeout error.

Please, let me know what can be the reason of serial communication problems.

Thanks,

Arev

[FuManWho]

Hi Arev,

I have a few questions about your situation:

1)Did you provide external power to the card as per the manual?:
https://www.ni.com/docs/en-US/bundle/ni-9871-getting-started/page/overview.html

2)Do you have a breakout for the RJ-50 connector?

3)Did you follow this guide for the serial loopback test?
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YFtECAW&l=en-US
Figure 3 being the wiring needed.

[arevh]

Hi Paolo,

Thank you for the response.

Actually I have already found the problem. There were some mistakes in the wiring.

Thanks,

Arev

[gustavo_quinonez]

Hi Arev,

I´m facing the same problem you described a while ago. Could you please tell me how you managed to overcome that situation?

Thanks in advance,

Gustavo

[arevh]

Hello Gustavo,

It appears there were wiring mistakes. I don't remember actual mistake though, as it was a while ago. Maybe differential lines were incorrectly wired, or something similar.

I suggest you also check the wiring, maybe again similar issues will be found.

Thanks,

Arev 

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