RS485

[DickerMoby]

I´m not sure if i´m right with my question.

I want to test a device with RS485 and need an example for the command

Command Frame Image 

DMY/STX/ID/Command data/EXT/BCC

DMY: Dummy data: 7Fh

STX : Start text: 02h

ID: Slave ID [2bytes]: (ASCII)

Command data: Variable length data: (ASCII)

EXT: End text: 03h

BCC: BCC error detection between ID and EXT (1 Byte)

Command Code  example "03" for INQUIRY (Reading)

Communication with Standard RS232 devices is no Problem for me. But These are clear ASCII commands. 

What for a string must i build for a INQUIRY command?

Thank you very much in advance

[GerdW]

Hi Moby,

are you related with NGHIA?

Apparently you want to use the very same communication protocol…

Read the manual attached by NGHIA, it describes the strings quite nicely. All you need to add is to put that DMY byte in front of the remaining string…

[DickerMoby]

I answered in wrong topic.

I'm Not related to the other User.

But it's a japanese device,too.

I will Check. For the Moment in need a rs485 USB Adapter. I only have rs232 connectors and Adapter.

Must i build an String with Hex values?

[GerdW]

Hi Moby,

you can build your string using hex values. Or you use string constants set to hex or \-code display mode...

[Hooovahh]

RS232 to RS485 converters are pretty common in our lab.  It would probably be more reliable to get a dedicated RS485 device, but we've used a couple converters like this one, and this one.  One works without power, just requiring two wires somehow.  The other I found needed a 12V adapter, but both work well for our low speed environmental chamber control.

[DickerMoby]

I´m sorry for late Reply. I was ill and some other things to do.

Now i tryed to get a simple command:

inquiry--->command code "03" It´s reading command

My adress is 01

But i don´t get back any feedback. I think something is wrong in command string?

[GerdW]

Hi Dicker,

I made the display style indicator visible for all string constants (as suggested before!):

Do you see the difference between them?

I think something is wrong in command string?

Yes, you are right!

- You need to set the string constants to hex display to be able to input correct values…

- you need to calculate the correct BCC value, trying to append an empty string is plain wrong!

- there are no error wires in your VI!

- using the default TermChar is wrong for this kind of communication…

- are you sure you need to read 20 bytes from your device?

[DickerMoby]

Hello Gerd,

yes i see the different in style and i read it before. But this versionw as wanted (seems to be wrong) 

According to my Manual ID and command data are ASCII  and not hex values. Now i don´t know how to handle.

Error wires are now connected. Cluster constant at Input and a Display output at visa read.

I reduced the reading buffer to 4 (Manual)

About term char: I had no Information in Manual. So i didn´t Change it. Now i set it to false.

BCC is also difficult to understand: It´s calculated in the Response between/including "ID" "RES" "DATA" "EXT"

-->ID=2bytes

-->RES=2bytes

-->data (for inquiry command) = 4bytes

-->EXT= no Information 

Now i´m thinking i must add "8" as string?

My error out is "-1073807339"  It´s meaning time out at "reading"

Best regards 

[GerdW]

Hi Dicker,

Now i´m thinking i must add "8" as string?

Why do you think so? Just because there are 8 bytes???

There should be a description in your manual telling you how to calculate the BCC. (Sometimes they just XOR all bytes…)

[DickerMoby]

Good afternoon Gerd,

I will Check the calculation again.

If i will mit find any Information i will ask manufacturer in Japan.

For the Moment i only counted the Bytes.

What's about my String Hex Problem?

Is PDF Upload here possible, 2-4pages?

Best regards