Read from a Power Meter with Modbus

[Wavicle]

Hi

I am trying to read power values from a power meter connected to the computer by a USB to rs485 converter. I am using the VI attached but I keep getting the following error: Error 56 occurred at RTU Data Unit.lvclass:Read ADU Packet.vi:5030001 with the possible reason: LabVIEW: The network operation exceeded the user-specified or system time limit. 

I don't know what I'm doing wrong and I'm stuck

Thank you

[MaSta]

LV 22.3? Why? New is not always good.

What I can say without having seen the code: I use ModBus a lot, also the ModBus VI set from NI. The problem most likely is not in the VIs.

[Kyle97330]

Error 56 is a TCP/IP error, but you say you are using a USB to RS485, which is Serial.  You probably need to correct your setup so you use a serial connection.

[Wavicle]

Yes, in the VI I posted I am creating a MODBUS serial master with the LabView VI. If I change the serial type it gives me the same error.

I don´t know if that is what you are referring to because I am new with all these connections.

[PalanivelThiruvenkadam]

Check for the "baud rate" and other serial Communication Parameters "Parity,Flow Control".

I have faced the similar issue when the Baud Rate was not Matching.

[Wavicle]

The baud rate, parity and stop bits match between the VI, the connector and the power meter. The only thing that I don't know is the flow control, I have it in "none" but there are a lot of options, maybe is another one?

[PalanivelThiruvenkadam]

How about Unit ID? Have you given the correct Unit ID.

[Wavicle]

I choose Unit ID as 1 but because I don't know where I can see what ID the power meter has. In the power meter I can set the address is that the same as unit ID? 

[K C]

Hi,

The ID and the Address are probably the same.

Normally you don't need flow control when using the ModBus protocol.

Still strange that you get error 56 which a TCP error.

Kees

[Wavicle]

In the NI MAX I select the connection, wich appears with the name ASRL3::INSTR, I try to test the connection with the VISA test panel an I get the following error: VISA: (Hex 0xBFFF0015) Timeout expired before operation completed. but even if set the timeout option to 20 seconds the error appears after less than 2 seconds.

Maybe the error is in the VI, something that I need to set in the MODBUS VIs?

Thanks