problem writing data to a function generator using GUI.

Hi everyone,

I wrote a GUI code that transfers an arbitrary waveform to a function generator. I use a slider button to change\select the amplitude of the waveform in real time. My problem is, that each time I touch the slider button, the (waveform) signal "jumps" for a short moment (I think to zero - it happens very fast) and only then changes to the selected value(confirmed it by conneting the function generator to a scope). It drives my laser crazy. How can I solve this problem? I think it may be related to the period of time in which the function generator reads the waveform data.

function CONST_Amp_Callback(hObject, eventdata, handles) %Set pulse amplitude
AM_Vpp= [-2.5 0];  %low and high voltages
n=16348; %temporal resolution (dont change)

ignition_pulse_amplitude = 1;   % fraction of full power
DAC_max=16383; 
waveform=zeros(1,n);
waveform(1:ignition_pulse_end_ind)=DAC_max.*ignition_pulse_amplitude;
waveform(ignition_pulse_end_ind+1:full_pulse_end_ind)=DAC_max.*lasing_pulse_amplitude;
handles.time = time;
handles.waveform = waveform;

if handles.DG1000Z.Value == 1
    
    DG1000Z_device = instrfind('Type', 'visa-usb', 'RsrcName', 'USB0::0x1AB1::0x0642::DG1ZA171301033::0::INSTR', 'Tag', '');
    
    % Create the VISA-USB object if it does not exist
    % otherwise use the object that was found.
    if isempty(DG1000Z_device)
        DG1000Z_device = visa('NI', 'USB0::0x1AB1::0x0642::DG1ZA171301033::0::INSTR'); %Create VISA object
        %% USB VISA descriptor can be checked using ULTRA software
    else
        fclose(DG1000Z_device);
        DG1000Z_device = DG1000Z_device(1);
    end
    WF_STR='DATA:DAC VOLATILE,'; %Digital to analog convertor
    for i=1:length(waveform)-1
        WF_STR=[WF_STR num2str(waveform(i)) ','];
    end
    WF_STR=[WF_STR num2str(waveform(end))];
    set(DG1000Z_device,'OutputBufferSize',length(WF_STR) + 40);
    fopen(DG1000Z_device);
    fprintf(DG1000Z_device,[':SOUR1:APPL:ARB ' num2str(n.*pulse_rep_rate) ] ); %Set the waveform of CH1 to ARB (arbitrary waveform)...
    fprintf(DG1000Z_device,'VOLT:UNIT VPP');
    fprintf(DG1000Z_device,['VOLT:HIGH ' num2str(AM_Vpp(2))]);
    fprintf(DG1000Z_device,['VOLT:LOW ' num2str(AM_Vpp(1))]);
    fprintf(DG1000Z_device,WF_STR);
    fprintf(DG1000Z_device,':OUTP1 ON'); %Turn on the output of CH1 of the function generator
    fclose(DG1000Z_device);
end

Thanks for helping!!

[Jan]

Without seeing any details of your implementation, how could we suggest a modification? There is no magic "do not cause jumps" switch in Matlab.

[Katherine Akulov]

Sorry, it is the first time i'm posting here. Here is the code of one of the buttons (I have a few buttons to chenge the duration and amplitude of the signal):

function CONST_Amp_Callback(hObject, eventdata, handles) %Set pulse amplitude
CONST_Amp_display_Callback(handles.CONST_Amp, eventdata,handles);
set(handles.CONST_Amp_display,'String',sprintf('%d',(get(handles.CONST_Amp, 'value'))));

AM_Vpp= [-2.5 0];  %low and high voltages
n=16348; %temporal resolution (dont change)

ignition_pulse_width=(handles.IGNITION_TIME.Value); %[msec]
ignition_pulse_width=ignition_pulse_width.*10^-3; %[sec]
pulse_length=str2double(handles.Pulse_Length.String); %[msec]
pulse_length=pulse_length*10^-3; %[sec]

if handles.radioConstAmp.Value == 1
    lasing_pulse_amplitude=(handles.CONST_Amp.Value).*10^-2;    % fraction of full power
elseif handles.radioFileAmp.Value == 1
    lasing_pulse_amplitude=0.7;
end
ignition_pulse_amplitude = 1;   % fraction of full power

DAC_max=16383; 
pulse_rep_rate=str2double(handles.Rep_Rate.String);
full_pulse_end_ind=round(pulse_length.*pulse_rep_rate.*n);
ignition_pulse_end_ind=round(ignition_pulse_width.*pulse_rep_rate.*n);

time=linspace(0,1./pulse_rep_rate,n);
waveform=zeros(1,n);
waveform(1:ignition_pulse_end_ind)=DAC_max.*ignition_pulse_amplitude;
waveform(ignition_pulse_end_ind+1:full_pulse_end_ind)=DAC_max.*lasing_pulse_amplitude;

handles.time = time;
handles.waveform = waveform;
plot(handles.time,handles.waveform)
if handles.DG1000Z.Value == 1
    set(handles.Device2,'Value', 0);
    
    DG1000Z_device = instrfind('Type', 'visa-usb', 'RsrcName', 'USB0::0x1AB1::0x0642::DG1ZA171301033::0::INSTR', 'Tag', '');
    
    % Create the VISA-USB object if it does not exist
    % otherwise use the object that was found.
    if isempty(DG1000Z_device)
        DG1000Z_device = visa('NI', 'USB0::0x1AB1::0x0642::DG1ZA171301033::0::INSTR'); %Create VISA object
        %% USB VISA descriptor can be checked using ULTRA software
    else
        fclose(DG1000Z_device);
        DG1000Z_device = DG1000Z_device(1);
    end
    
    WF_STR='DATA:DAC VOLATILE,'; %Digital to analog convertor
    for i=1:length(waveform)-1
        WF_STR=[WF_STR num2str(waveform(i)) ','];
    end
    WF_STR=[WF_STR num2str(waveform(end))];
    
    set(DG1000Z_device,'OutputBufferSize',length(WF_STR) + 40);
    fopen(DG1000Z_device);
    fprintf(DG1000Z_device,[':SOUR1:APPL:ARB ' num2str(n.*pulse_rep_rate) ] ); %Set the waveform of CH1 to ARB (arbitrary waveform)...
    fprintf(DG1000Z_device,'VOLT:UNIT VPP');
    fprintf(DG1000Z_device,['VOLT:HIGH ' num2str(AM_Vpp(2))]);
    fprintf(DG1000Z_device,['VOLT:LOW ' num2str(AM_Vpp(1))]);
    fprintf(DG1000Z_device,WF_STR);
    fprintf(DG1000Z_device,':OUTP1 ON'); %Turn on the output of CH1 of the function generator
    fclose(DG1000Z_device);
end

When I used an oscilloscope to observe the function generator's pulses, I noticed a "jump" and after it, the desired pulse. This "jump" drives the laser (which is powered by this pulse) crazy.