modbus

[J. Z.]

Hello,

I try to connect a bronkhorst Cori-flow meter with a CompacRio (with a NI9871 card, FPGA). I use a regular Modbus program. I get no communication with the Cori-flow meter. The settings for the communication with the cori-flow meter are: broadcast support yes, baud rate 19200, parity even, transmission mode RTU, interface RS485 2W cabling, modbus register unsigned int. Setings off the time out is 200 mSec (in the modbus program).

Can anyone explane why i can't get any communication?

Thank you in advance

Jeroen

[ninlmartijn]

Hi J.Z.

Are you using the example from this KB ?

Best regards,

[J. Z.]

Hallo Martijn,

Het voorbeeld waar jij naar verwijst, gebruik ik inderdaad. Het is een standaard modbus protocol van jullie.

Groeten, Jeroen

[K C]

Hi Jeroen,

Is it possible that you send hexa data to your device ?

If your device supports the loopback command (it should) you can try sending the next hexadecimal string (for slave 1)

01, 08, 00, 00, AA, 55, 5E, 94

Your device should return the same string.

You can also double check the interface parameters and cable connections. Did you terminate the RS-485 network correctly ?

btw. I hope you know that there is also a Dutch LV forum here.

Groeten, Kees

[Quintino]

Hello J.Z.

I'm having the same problem. I have the cRIO-9074 with the NI-9871 module, and I'm using the same Modbus Communication Reference Example for cRIO, but with no success. I've created a topic RS-485 ModBus with NI-9871 on cRIO-9074 but no one replies. After contacting the support in France I really believe that the NI software is not working properly with this modules with Modbus under RS-485.

For now I just hope they solve this software problem fast.

Best of luck with the communication.

André Quintino.

[johnnywintel]

Hi,

are You sure You use the right cable? Bronkhorst usually uses 8-pin RJ45 connectors, but the NI9871 module has a 10-pin RJ50 connector.

All the best!

Johnny