visasession

[MarkMLl]

Those are just USB vendor IDs: https://the-sz.com/products/usbid/index.php?v=0X0699&p=&n=
But I wouldn't trust that, but instead rely on the *IDN? result

May I ask a supplementary question here?

I believe that *IDN is mandatory, and I believe that I understand its output format.

What I'm far less happy about is the various status registers that this family of protocols (generally derivatives of HP-IB etc.) implements: which of those are really mandatory, and what is the expected response if a non-mandatory one isn't implemented?

MarkMLl

[Laksen]

IEEE 488.2 specifies the mandatory functions as well as the syntax and capitalization rules. I think all will support *IDN? Which will make it possible to detect quirky implementations

Especially low-cost manufacturers tend to ignore the standard very often, Rigol and R&S are some of the worst in my experience

If you call an invalid command or query you should be able to query *STB? to see if there's an error, whether the command completed or if there's a response waiting in the output buffer to be read. But that is problematic on for example ASRL and raw sockets where there isn't a way to query STB without overwriting the output buffer.
On GPIB, USB, VXI11/hislip there is an out of band way of reading STB

[CM630]

As no suprise, when I dropped the VISA control on the panel it did not work.
So I had to add LoadVisaLib;.
Respectively I added unLoadVisaLib, too.

Code: Pascal  [Select][+][-]

1. constructor TVisaSession.Create(AOwner: TComponent);
2. begin
3.    inherited Create(AOwner);
4.    LoadVisaLib;
5.    fThrowException := true;
6.    fLock := TCriticalSection.Create;
7.    fActive := false;
8.    fAddress := '';
9.    fHandle := 0;
10.    fConnectTimeout := 2000;
11. end;
12.  
13. destructor TVisaSession.Destroy;
14. begin
15.    fThrowException := false;
16.    Active := false;
17.    unLoadVisaLib;
18.    fLock.Free;
19.    inherited Destroy;
20. end;  

And maybe :

Code: Pascal  [Select][+][-]

1.  published
2. ...
3.   property VisaDLL: string read fVisaName write SetVisaName;
4.  end;  

...
I believe that *IDN is mandatory, and I believe that I understand its output format.
...

I had absolutely no experience with Visa until this week, but as I wrote, the R&S did not respond to the *IDN?. Indeed, I have not even read the specs of the device, just plugged it in.

[MarkMLl]

So STB /must/ be accessible. Do you have any comment on the rest of http://www.av.it.pt/medidas/data/Manuais%20&%20Tutoriais/40b%20-%20VNA%20-%20ZVB20/CD/documents/Help_Files/WebHelp_ZVB/Remote_Control/Status_Reporting_System/Status_Reporting_System.htm#Structure which appears to be a fairly concise summary?

I'm considering it in the context of https://github.com/MarkMLl/scpisrv , and wondering whether I could usefully add a register handling unit assumed to apply to all devices.

MarkMLl

[CM630]

...
I'm considering it in the context of https://github.com/MarkMLl/scpisrv , and wondering whether I could usefully add a register handling unit assumed to apply to all devices.
...

So you have an app which reads data from serial measurement devices and wonder if you could extend it to using VISA devices, too?

[MarkMLl]

...
I'm considering it in the context of https://github.com/MarkMLl/scpisrv , and wondering whether I could usefully add a register handling unit assumed to apply to all devices.
...

So you have an app which reads data from serial measurement devices and wonder if you could extend it to using VISA devices, too?

No. I have a library that can be integrated with programs supporting various devices.

MarkMLl

[CM630]

I cannot figure out how to get an event when data is available.
I tried viEnableEvent with no success.
I need it, because I do not know when the trigger of an oscilloscope will be activated (Query is not applicable). The other option I can think of is checking periodically if data has been received in a timer.

[Laksen]

What communications protocol are you using? SRQs don't work through serial for example

[MarkMLl]

Interesting. https://helpfiles.keysight.com/csg/N52xxB/Programming/GPIB_Example_Programs/Socket_Client.htm looks like it might be relevant at least at the SCPI layer: in short the software asks the instrument what port to use, and waits for asynchronous messages to arrive on it.

MarkMLl

[CM630]

What communications protocol are you using? SRQs don't work through serial for example

Tektronix TBS xxxx over USB. If this happens to answer the question, which I do not understand.
USB0::0x0699::............

[Laksen]

This for example should call the SRQ handler when bit 4 (MAV) in the STB byte gets set. This will be done when the instrument responds to the *STB? query. Likewise you could probably use this some way to trigger on a different bit in the instrument status tree (very instrument specific)

Code: Pascal  [Select][+][-]

1. function handler(vi: ViSession; eventType: ViEventType; event: ViEvent; userHandle: ViAddr): ViStatus; stdcall;
2. begin
3.   writeln('Event!');
4.   result:=0;
5. end;
6.  
7. begin
8.   visa.viInstallHandler(v, VI_EVENT_SERVICE_REQ, @handler, nil);
9.   visa.viEnableEvent(v, VI_EVENT_SERVICE_REQ, VI_HNDLR, 0);
10.  
11.   instr.Command('*SRE 16');
12.   instr.Command('*STB?'); // Handler should be called now since output buffer gets filled
13. end.
14.  

[CM630]

Thanks!
I did not understand how to execute your code as you wrote it.
So I added

Code: Pascal  [Select][+][-]

1.  TVisaSession = class(TComponent)
2. ...
3. public
4. ...
5.   property Handle: ViSession read fHandle;
6. ...

And then here is a snippet:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls,
9.   visa,session,visatype;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     Button1: TButton;
17.     Memo1: TMemo;
18.     procedure Button1Click(Sender: TObject);
19.     procedure FormCreate(Sender: TObject);
20.   private
21.  
22.   public
23.  
24.   end;
25.  
26. var
27.   Form1: TForm1;
28.     MyVisaSession : TVisaSession;
29.  
30. implementation
31.  
32. {$R *.lfm}
33.  
34. { TForm1 }
35.  
36. function event_handler(vi: ViSession; eventType: ViEventType; event: ViEvent; userHandle: ViAddr): ViStatus; stdcall;
37. begin
38.   form1.Memo1.Append ('Event: ' + MyVisaSession.Read);
39.   result:=0;
40. end;
41.  
42. procedure TForm1.FormCreate(Sender: TObject);
43. begin
44.   Memo1.ScrollBars := ssBoth;
45.   Memo1.WordWrap := false;
46.   Memo1.Clear;
47.   Memo1.Refresh;
48.   MyVisaSession := TVisaSession.Create(nil);
49.   MyVisaSession.Address :='USB0::0x0699::........';
50.   MyVisaSession.Active := True;
51.   visa.viInstallHandler(MyVisaSession.Handle , VI_EVENT_SERVICE_REQ, @event_handler, nil);
52.   visa.viEnableEvent(MyVisaSession.Handle, VI_EVENT_SERVICE_REQ, VI_HNDLR, 0);
53.   visa.viDiscardEvents(MyVisaSession.Handle, VI_EVENT_SERVICE_REQ,VI_HNDLR);
54. end;
55.  
56. procedure Wait(Duration: QWord);
57. var
58.   StartTick: QWord;
59. begin
60.   StartTick := GetTickCount64;
61.   repeat
62.     Application.Processmessages;
63.   until GetTickCount64 > (StartTick + Duration);
64. end;
65.  
66. procedure TForm1.Button1Click(Sender: TObject);
67. begin
68.   MyVisaSession.Command('*RST;');
69.   Wait(500);
70.   MyVisaSession.Command('*SRE 16');
71.   MyVisaSession.Command('*STB?'); // Handler should be called now since output buffer gets filled
72.   Wait(50);
73.   MyVisaSession.Command('*IDN?');
74.   Wait(50);
75.   MyVisaSession.Command('*ESR?');
76.   Wait(50);
77.   MyVisaSession.Command('EVM?');
78.   Wait(50);
79.   MyVisaSession.Command('*OPC');
80.   Wait(50);
81.   MyVisaSession.Command(':HOR:RECO 5000000;:HOR:SEC 0.040000;:HOR:DEL:MOD OFF;POS 2.000000');  //Configures the record properties of the acquisition subsystem.
82.   //                                            time/div
83.   Wait(50);
84.   MyVisaSession.Command(':SEL:CH1 ON;:CH1:PRO:GAIN 1.00000;:CH1:COUP DC;SCA 1.500000;OFFS 0.000000;BAN TWE;DESK 0.000000;');
85.   //                                          probe 1X                  v/div
86.   Wait(50);
87.   MyVisaSession.Command('WFMO:BYT_N?;NR_P?;YOF?;YMU?;YZE?;XIN?;XZE?');
88.   Wait(50);
89.   MyVisaSession.Command('CURV?');
90. end;
91.  
92. end.

It succeeds in getting an untriggered waveform, I have not tried with a triggered one yet.

[CM630]

I have a snippet which almost works.
It gets the data when the trigger is activated it starts to draw it in a TAChart.
But it causes an exception in TAChart.
The data seems valid - if I write the raw string received by the oscilloscope to a file and then load it and process it, there is no issue with TAChart, everything is fine.
Also, if I enable wait(1); in procedure PlotWaveForm the chart is drawn correctly, alas, that takes a lot of time.

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, StrUtils,
9.   TAGraph, TASeries, visa_dyn, session, visatype,
10.   TADrawUtils, TACustomSeries;
11.  
12. type
13.  
14.   { TForm1 }
15.  
16.   TForm1 = class(TForm)
17.     Button1: TButton;
18.     Chart1: TChart;
19.     Chart1LineSeries1: TLineSeries;
20.     Label1: TLabel;
21.     VisaSession: TVisaSession;
22.     procedure Button1Click(Sender: TObject);
23.     procedure FormCreate(Sender: TObject);
24.   private
25.  
26.   public
27.  
28.   end;
29.  
30. var
31.   Form1: TForm1;
32.   WaitWaveform: boolean;
33.  
34.  // function VisaEventHandler(vi: ViSession; eventType: ViEventType; event: ViEvent; userHandle: ViAddr): ViStatus; stdcall;
35. implementation
36.  
37. {$R *.lfm}
38.  
39. { TForm1 }
40.  
41. procedure Wait(Duration: QWord);
42. var
43.   StartTick: QWord;
44. begin
45.   StartTick := GetTickCount64;
46.   repeat
47.     Application.Processmessages;
48.   until GetTickCount64 >= (StartTick + Duration);
49. end;
50.  
51. procedure PlotWaveForm(WaveformData: string);
52. var
53.   i: integer;
54.   plotdata: array of double;
55.   dt : double = 10/1000;
56.   plotindex: integer = -1;
57.   numstring: string ='';
58.   DataOffset: integer = 0;
59. begin
60.   form1.Chart1LineSeries1.Clear;
61.   form1.Label1.Caption := format('Plotting the waveform...%d samples received',[Length(WaveformData)]);
62.   if LeftStr(WaveformData,1) <> '#' then
63.   begin
64.     form1.Label1.Caption := 'Received data is invalid';
65.     exit;
66.   end;
67.   DataOffset := StrToInt(midstr(WaveformData,2,1)) + 2;
68.   SetLength(plotdata,Length(WaveformData)-DataOffset);
69.   plotindex := -1;
70.   for i:=DataOffset to high(WaveformData)-1 do //Last value is always #10 and it is not a part of the data.
71.     begin
72.        inc(plotindex);
73.         plotdata[plotindex] := Int8(WaveformData[i]);
74.         form1.Chart1LineSeries1.AddXY(plotindex,plotdata[plotindex]);
75.         //wait(1); //TAChart does NOT crash if I enable this line, but execution is extremely slow. Even if Application.Processmessages; within Wait is commented, the app does NOT crash.
76.         form1.Label1.Caption := IntToStr(i);
77.         numstring := numstring + FloatToStr(plotdata[plotindex]) +',0,'+ #13#10;
78.     end; //for
79.   form1.Label1.Caption := 'Ready';
80. end;
81.  
82. function VisaEventHandler(vi: ViSession; eventType: ViEventType; event: ViEvent; userHandle: ViAddr): ViStatus; stdcall;
83. var
84.   WaveformData: AnsiString = '';
85. begin
86.   if (WaitWaveform = true) then
87.   begin
88.     WaitWaveform := false;
89.     WaveformData := Form1.VisaSession.query('CURV?');
90.     PlotWaveForm(WaveformData);
91. end;
92. end;
93.  
94. procedure TForm1.FormCreate(Sender: TObject);
95. begin
96.   WaitWaveform := false;
97.   if not LoadVisaLib then
98.   begin
99.     ShowMessage ('CannotLoadVisaLib');
100.     exit;
101.   end;
102.   //VisaSession.Address := 'USB0::0x0699::......'; //Or set it as a property of the control
103.   VisaSession.Active := true;
104.   VisaSession.EnableEventHandler(@VisaEventHandler);
105. end;
106.  
107. procedure TForm1.Button1Click(Sender: TObject);
108. var
109.   myfs: TFormatSettings;
110.   dt : double = 10/1000;
111. begin
112.   Label1.Caption := '';
113.   WaitWaveform:= false;
114.   myfs.DecimalSeparator := '.';
115.   VisaSession.Command('*RST;');
116.   VisaSession.Command('*CLS;:HEADER OFF;:WFMO:ENC BIN');   //Default setup
117. //  VisaSession.Command('CH1:POS -2.500000'); //Vertical offset
118.   VisaSession.Command(':SEL:CH1 ON;:CH1:PRO:GAIN 1.00000;:CH1:COUP DC;SCA 0.500000;OFFS 0.000000;BAN TWE;DESK 0.000000;');
119. //                                            probe 1X                  v/div
120.   VisaSession.Command(':ACQ:STOPA SEQ'); //':ACQ:STOPA RUNST'   //Disable/enable continuous acquisition
121.   VisaSession.Command(':ACQ:MOD SAM;'); //Configures the common properties of the acquisition subsystem.
122.   //                        //# samples
123.   VisaSession.Command(':HOR:RECO 20000;:HOR:SEC ' + FormatFloat('0.000000',dt,myfs) + ';:HOR:DEL:MOD OFF;POS 2.000000');  //Configures the record properties of the acquisition subsystem.
124.  
125.   VisaSession.Command(':TRIG:A:EDGE:SOU CH1;:TRIG:A:LEV 0.500000;:TRIG:A:EDGE:SLO RISE;:TRIG:A:EDGE:COUP DC;'); //Set the trigger and wait until it is triggerred
126.   VisaSession.Command(':DATA:SOU CH1;:DATA:START 1.000000;:DATA:STOP 5000000.000000;'); //probably this sets the buffer size
127.   VisaSession.Command('ACQUIRE:STATE OFF;ACQuire:STOPAfter SEQuence;SELECT:CH1 ON');
128.   //
129.   VisaSession.Command('DESE 1'); //Set registers to await an Operation Complete (OPC) event (bit 1) in the event queue. This event is summarized in the Event Status Bit(ESB) of the Status Byte Register.
130.   VisaSession.Command('*ESE 1'); //Set the Event Status Bit (bit 5) to await a Service Request (SRQ)
131.   VisaSession.Command('*SRE 0'); //Clear the event registers
132.   VisaSession.Command('ACQUIRE:STATE ON');
133.   Wait(50);
134.   VisaSession.Command('*SRE 16');
135.   VisaSession.Command('*STB?'); // Handler should be called now since output buffer gets filled
136.   Wait(50);
137.   Label1.Caption := 'Waiting for a waveform...';
138.   VisaSession.Command('*OPC');
139.   Wait(50);
140.   WaitWaveform:= True;
141.   VisaSession.Command('*OPC?'); //Waits for the trigger
142. end;
143.  
144. end.
145.  

Maybe the inability to declare function VisaEventHandler(vi: ViSession; eventType: ViEventType; event: ViEvent; userHandle: ViAddr): ViStatus; stdcall; as a part of the form is related (https://forum.lazarus.freepascal.org/index.php/topic,70205.msg547515.html#msg547515) ?


EDIT: It is not TAChart's fault, I tried to populate the data in a StringGrid, it just freaks out.
I tried several DLLs, still no improvement.
I tried static binding to the *VISA32.dll, still the same.

EDIT 2: An example with a working trigger is attached.

[CM630]

Can FP-VISA handle Visa TCP Socket connection?

From a quick glimpse:

Code: Pascal  [Select][+][-]

1. function TVisaSession.Read: string;
2. var res: ViStatus;
3. begin
4.    result := '';
5.    repeat
6.       result := result + recv(1024, res);
7.    until (res <> VI_SUCCESS_MAX_CNT) and (res <> VI_SUCCESS_TERM_CHAR);
8. end;

I have got the impression that for Socket connection it shall rather be until (res <> VI_SUCCESS_MAX_CNT) and (res <> VI_SUCCESS_TERM_CHAR); and also terminations characters shall be settable somehow.


EDIT: I tried

Code: Pascal  [Select][+][-]

1.          CheckError(viSetAttribute(fHandle,VI_ATTR_TERMCHAR_EN,VI_TRUE));
2.          CheckError(viGetAttribute(fHandle,VI_ATTR_TERMCHAR_EN,@attrval));

viGetAttribute does not return the value provided in viSetAttribute . (attrval is something unrelated).
On the other hand, if I do (just for a test):

Code: Pascal  [Select][+][-]

1.          CheckError(viSetAttribute(fHandle, VI_ATTR_TMO_VALUE, 120000));
2.          CheckError(viGetAttribute(fHandle,VI_ATTR_TMO_VALUE,@attrval)) ;

attrval returns 120000, so it seems to me that I am using viSetAttribute and viGetAttribute the right way.