FP-VISA - A simple component to connect to VISA instruments

[Laksen]

I've done a simple header conversion for VISA, and implemented a small component to make it easy to communicate with SCPI instruments.

For now the header only supports windows, uses static linking, and has some known bugs, but it should be crossplatform with minimal changes. Feel free to send me a pull request if you get it working on Linux and mac

Over the years I've had great use of it for experiments, so here it is:
https://github.com/Laksen/FP-VISA

[kamischi]

This is great and will replace my miniVisa headers, which i created for a test. Unfortunately, i did not succeed to install the drivers for an Agilent USB-Daq box on Windows and we finally switched to a cheap non-VISA box from BMC. I also tried to use the Agilent box from Mac OS X, but no success either. Maybe, I have another go at it, since I have a project with high school students with Delphi background. Besides naming the library, I expect no further changes for Mac OS X and Linux.

MiSchi

[Laksen]

Sounds strange. I've never had any problems with Agilent/Keysight's IO Libraries.

Did you try NI's VISA implementation instead?

[marcov]

Btw, units like VISAtypes become increasingly redundant now that both FPC and current Delphi versions (say since XE2) have a full set of (u)int8..(u)int64 types defined.

[Laksen]

Sort of agreed, but it's just to provide actual visa compatible types, like viUint8, etc.

[Fred vS]

I've done a simple header conversion for VISA

WOW, great project, many thanks.

Fred

[exdatis]

I've got an error: error in type definition (RawByteString)
win7 32 bit, Lazarus 1.2.4, FPC 2.6.4, svn: 45510

[Laksen]

Fixed that.

[exdatis]

Thank you very much, Laksen! Also, thank you for your effort and sharing.

[kamischi]

Sounds strange. I've never had any problems with Agilent/Keysight's IO Libraries.

Did you try NI's VISA implementation instead?

In the end, I suspect that some Virus protection or such was the actual problem. However, I am not expert on that, I did not have access to the system for longer time and it wasn't my system and i did not want to take responsibility for wrecking it. But it sounds like i should give it another try on a system, where I am in a more powerful situation.

MiSchi

[dodgeydave]

Hi.

Have been looking at this, and eventually managed to make it work with serial communications via NI's VISA Library on Win10.
(It is easier for me to develop code with some simple emulators attached by a serial link, before letting rip with expensive high power GPIB connected kit...)

Especially as I see NI now have a VISA download for Debian Linux and derivatives.  Yet to be explored...  (On a sacrificial 'nix install!)

It took a while, as I could not find an way to manipulate a serial port's settings (speed, data bits, parity etc) as VISA's SetAttributes call's need a handle relating to the instance of the VISA session, that in turn, I could not find any way to identify from outside the VisaSession code.   So, I added it..

In the session unit, under public. I added...

Code: Pascal  [Select][+][-]

1.    function GetHandle: ViSession;
2.  

In the Implementation part, I added

Code: Pascal  [Select][+][-]

1. function TVisaSession.GetHandle: ViSession;
2. Begin
3.    result := fHandle;
4. end;
5.  

I can now access the needed handle for the VISA call's to manipulate the serial port settings, and all is well.

(I guess I could have just moved fHandle from the private deceleration to public, but I can see potential issues doing that...  But if the brains trust say that's OK, I'll go that way instead.)

Anyway...
In the projects Unit1.pas

Code: Pascal  [Select][+][-]

1.    VisaSession1.Address := 'ASRL4::INSTR'  // Windows COM4
2.    
3.       VisaSession1.Active := True;
4.       If Status = VI_SUCCESS then begin
5.          viHandle := VisaSession1.GetHandle;
6.  
7.          status := viSetAttribute(viHandle, VI_ATTR_ASRL_PARRITY, VI_ASRL_PAR_ODD);
8.  
9.  

etc..  Things now work as NI document with serial ports...

NOTE!  The above is not Copy/Pasted from with a Lazarus project, but fat finger transcribed from one PC to another, so errors and commissions may have occurred, as well as spulling mistooks.

If someone can come up with a reason why not to do access the session handle that way, OK..  But what is the accepted alternative?   As I've not yet found any documentation for FP-Visa at all, other than the sources on Github, where such info is sadly missing.

Otherwise, if anyone wants, I can provide the working example code, so far, for those who like to laugh at others attempts, or wish to play with...

Regards to All.

DodgeyDave.

I've done a simple header conversion for VISA, and implemented a small component to make it easy to communicate with SCPI instruments.

For now the header only supports windows, uses static linking, and has some known bugs, but it should be crossplatform with minimal changes. Feel free to send me a pull request if you get it working on Linux and mac

Over the years I've had great use of it for experiments, so here it is:
https://github.com/Laksen/FP-VISA

[MarkMLl]

Nicely done. I've got older test equipment which I normally talk to via a cheap IEEE-488 adapter.

MarkMLl

[Kepsz]

Thanks Lasken for this component!

Btw, it is not documented at all, so I wrote a simple program.

Steps:
-Install Ni-Visa from here: https://www.ni.com/en/support/downloads/drivers/download.ni-visa.html#484351
-Reboot, connect your USBTMC capable device. In my case, that is a Siglent SPS5051X
-Open VISA Interactive Control, and look for the "USB Instrument Resource". That is the address of the device. For my device, it is: USB0::0xF4EC::0x1453::SPS51ABD6R0511::INSTR
-Download the FP-VISA package from Lasken's repo: https://github.com/Laksen/FP-VISA
-Open the .lpk package file in lazarus, then choos install and rebuild the IDE.
-Now you can drga-and-drop the TVisaSession object from the Lazarus toolbar.

Verry basic code to read ID, read / set voltage on CH1 and turn CH1 On/Off on an already connected and powered device:

Code: Pascal  [Select][+][-]

1. unit main;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, session,
9.   LazLogger;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     SetVolt: TButton;
17.     IdData: TEdit;
18.     Output: TToggleBox;
19.     VoltageData: TEdit;
20.     Label1: TLabel;
21.     Label2: TLabel;
22.     ReadVolt: TButton;
23.     VisaSession1: TVisaSession;
24.     procedure FormCreate(Sender: TObject);
25.     procedure FormShow(Sender: TObject);
26.     procedure OutputClick(Sender: TObject);
27.     procedure ReadVoltClick(Sender: TObject);
28.     procedure SetVoltClick(Sender: TObject);
29.   private
30.  
31.   public
32.  
33.   end;
34.  
35. const
36.   ADDRESS = 'USB0::0xF4EC::0x1453::SPS51ABD6R0511::INSTR';
37.  
38. var
39.   Form1: TForm1;
40.  
41. implementation
42.  
43. {$R *.lfm}
44.  
45. { TForm1 }
46.  
47. //create object
48. procedure TForm1.FormCreate(Sender: TObject);
49. begin
50.   VisaSession1 := TVisaSession.Create(nil);
51. end;
52.  
53. //activate connection, read device identifier
54. procedure TForm1.FormShow(Sender: TObject);
55. begin
56.    VisaSession1.Address := ADDRESS;
57.    VisaSession1.Active := True;
58.    IdData.Caption := VisaSession1.Query('*IDN?');
59. end;
60.  
61. //read the measured voltage
62. procedure TForm1.ReadVoltClick(Sender: TObject);
63. begin
64.    VoltageData.Caption := VisaSession1.Query(':MEASure:VOLTage? CH1');
65. end;
66.  
67. //sets CH1 voltage
68. procedure TForm1.SetVoltClick(Sender: TObject);
69. begin
70.    VisaSession1.Write(':SOURce:VOLTage:SET CH1,' + VoltageData.Caption);
71.    VoltageData.Caption := VisaSession1.Query(':MEASure:VOLTage? CH1');
72. end;
73.  
74. //On-Off CH1
75. procedure TForm1.OutputClick(Sender: TObject);
76. begin
77.    if Output.Checked then begin
78.      VisaSession1.Write('OUTPut 1');
79.    end else begin
80.      VisaSession1.Write('OUTPut 0');
81.    end;
82. end;
83.  
84. end.

[Ilya83]

Can someone show an example of catching errors using this component?
Device is not connected or connection lost errors for ex.

I've tryed:

try
        VisaSession1 := TVisaSession.Create(nil);
     except
       on E: EVisaException do ShowMessage(E.Message);
     end;       

Not working.

And can I use this component to manage several devices?

I think I need to open and close sessions. Or it should be one session for all devices and then just manage it by

VisaSession1.Address := NEW_ADDRESS;
   VisaSession1.Active := True;