Communication to device using RS-232 to USB Converter

[wolfgang2021]

*Edit to the previous post*

I'm sorry but I don't have much experience in LabVIEW and there is much I can still learn. I really appreciate your help. What type of constant would I need to put into the index of the index array function, and what numbers would I need to add to the Join Numbers function where it says hi and low? Here is an updated picture of the program so far.

[Dennis_Knutson]

As stated in the manual, bytes 4 and 5 are the measurement bytes. You drag down the Index Array function to get two inputs (and two outputs). Wire a constant 4 to the first input. The second input will default to 5 even if you don't wire anything there. The first output of the index array goes to the first input of the join numbers and the second output of the index array goes to the second input of join numbers.

And as I have mentioned a couple of times, none of this will do you any good until you synch up with what is being transmitted. Just doing a read of 9 bytes will not do that. Since the instrument is always transmitting, you have no idea of the initial byte order. Synching is going to be a complicated process. You might want to read a single byte until the value read is 7. Then read 8 bytes and see if the last byte (the checksum) is correct. If not, repeat.

[wolfgang2021]

According to the manual on page 32 the formula is 10^((hix256+lo)/4000-12.5), how am I suppopse to get the 10^ part of the formula in the program and how am I supposed to multiply the hi byte by 256 in the program? Dose the synch look alright now? Here is an updated picture.

[Dennis_Knutson]

The power of 10 is something I missed. The answer is to use the Power of 10 function.

You don't need to multiply by 256. The join takes care of that.

You aren't doing any synching at all. You simply cannot do the synch with a single read. I've stated this before. It will take the quite complicated process I outlined in the previous post. You will need to gain some LabVIEW experience in order to do it.

[wolfgang2021]

Can you please help show me how to do this synch? I really need to get this gauge up and running. Any help would be gladly appreciated.

Thanks,

Chet

[Dennis_Knutson]

I'm not able to provide any code. I would suggest you try to implement the process I described. You can do a search for checksum and find several code examples of that.

Unfortunately, you've picked an instrument that is one of the difficult ones to use.

[VT_Chemist]

Chet,

I am also developing LV code to read inficon gauges.  I have not yet figured out how to sync, but I can post a crude example showing how to extract the pressure as soon as I can get it. 

[VT_Chemist]

Chet,

Please find attached LV code (v 8.6.1) for reading inficon gauges.  I have also attached a graphic if you cannot open the vi.  The program is designed to read an excess number of bytes, and then locate the checksum, from which it can determine the pressure high and low bytes.  From there, it is a simple task to convert to pressure (in this case, mbar).

Regards,

Wes