REXYGEN Community Forum

jaroslav_sobota

Administrator

Registered: 2015-10-27

Posts: 535

Re: REXLANG dynamically assign variable by looping thru txt file

coldh2odvr: In your case the pi user is not allowed to read the file /rex/rexcore/values.txt, see the line

-rw-r----- 1 root root    0 May  5 17:10 values.txt

in your output. In that case you have to use "sudo cat ...".

In my case the pi user can at least read the file, see my output:

-rw-r--r-- 1 root root 1682 May  5 14:15 values.txt

But RexCore runs with root privileges so it can access the file without any problem on both machines. Therefore the only problem was that your file was empty. The question is why? How did you download the example and transfer the files to the RPi?

Btw what pressure gauge are you using? What analog signal does it provide?

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Monarco HAT for Raspberry Pi - Lightweight I/O for monitoring, archiving and control.
Raspberry Pi in industrial automation!

tomáš čechura

Administrator

Registered: 2016-02-22

Posts: 371

Re: REXLANG dynamically assign variable by looping thru txt file

I'm sorry, I should have told that I'm running everything on Windows now ...

That's perfectly fine - it should be working on Windows as well

On Windows machine the current look up directory is set to ProgramDara directory e.g.

C:\ProgramData\REX Controls\REX_2_10_8_5910\RexCore\

so the "values.txt" file should be stored here. Then the example should be working as well.

Cheers, Tomas

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Raspberry Pi as a miniature industrial PC. Analog and digital I/O, RS-485 and 1-Wire bus.

coldh2odvr

Member

Registered: 2016-04-18

Posts: 17

Re: REXLANG dynamically assign variable by looping thru txt file

But RexCore runs with root privileges so it can access the file without any problem on both machines. Therefore the only problem was that your file was empty. The question is why? How did you download the example and transfer the files to the RPi?

I used the compile and download function in RexDraw. Since the files appeared on the Pi, I assumed it was transferring them while sending the program.

Btw what pressure gauge are you using? What analog signal does it provide?

I'm reading from an Inficon PSG 500, it outputs a 0-10V signal where P(mTorr) = 10^((V-2.448)/1.286). The PLC reads voltage but can't do the exponentials needed to do the conversion to mTorr, hence the lookup table. I'm not currently controlling anything with the gauge but I need a pressure display.

coldh2odvr

Member

Registered: 2016-04-18

Posts: 17

Re: REXLANG dynamically assign variable by looping thru txt file

Hi Tomas,

Thanks for the WinSCP tip very helpful.

tomáš čechura

Administrator

Registered: 2016-02-22

Posts: 371

Re: REXLANG dynamically assign variable by looping thru txt file

Hey coldh2odvr,

I'm glad that I could help you. I have one more tip for you.

We have recently launched Indiegogo campaign with an add-on board for Raspberry Pi called Monarco. It can help you to interface your pressure gauge directly to Raspberry Pi thanks to analog inputs. Check the Monarco HAT campaign site for more detail about the product.

I also prepared a sample project for you on how to compute the pressure in REX according to the formula from your previous post:

P(mTorr) = 10^((V-2.448)/1.286)

pressure_measurement.zip

Please feel free to contact me if you need any further information.

Regards, Tomas

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Raspberry Pi as a miniature industrial PC. Analog and digital I/O, RS-485 and 1-Wire bus.