How to change a parameter while the signal is running?

Hello everyone,

I want to generate a signal that can be changed while running. I want to be able to change the magnitude while the signal is running. I tried generating a signal in background and i wrote different values for the magnitude in the command box but it didn't change anything.

I have the following code:-

%-------------------------------------

clearvars

clc

d = daqlist("ni");

deviceInfo = d{1, "DeviceInfo"};

dq = daq("ni");

fidData = fopen("logData.bin","w");

fidTime = fopen("logTime.bin","w");

DisplayTime=1;

s = daq.createSession('ni');

s.Rate=5000;

addAnalogInputChannel(s,'Dev2','ai11','Voltage');

lh = addlistener(s,'DataAvailable',@plotData);

lh1 = addlistener(s,'DataAvailable',@(src, event)logData(src, event, fidData,fidTime));

s.IsContinuous=true;

s.NotifyWhenDataAvailableExceeds=floor(DisplayTime*s.Rate);

%Output

addAnalogOutputChannel(s,'Dev2','ao0','Voltage');

Fs=s.Rate

t1=100;

t = 0 :1/Fs : t1-1/Fs;

A=0.5;

data0 = A*sin(2*pi*t*159.2)';

b=repmat(data0,5,1);

queueOutputData(s,b);

datagiver = addlistener(s, 'DataRequired',@(src,event)...

src.queueOutputData(b));

figure(1)

clf

startBackground(s);

%%

s.stop

fclose(fidData);

fclose(fidTime);

%-------------------------------------

Please help if you have an idea. I need to do this because im making a controller for the magnitude value.

Regards

Ali

Answer 1

[Satwik]

Hi,

In order to dynamically change the magnitude of the output signal while the DAQ session is running, we need to modify the queued output data in real-time. This can be accomplished by updating the data in the 'DataRequired' event. Below is a modified version of the code to achieve this, with comments explaining the changes made:

% Setup code for the session same as before

% Add listeners for data available and logging
lh = addlistener(s, 'DataAvailable', @plotData);
lh1 = addlistener(s, 'DataAvailable', @(src, event) logData(src, event, fidData, fidTime));

% Set session properties
s.IsContinuous = true;
s.NotifyWhenDataAvailableExceeds = floor(DisplayTime * s.Rate);

% Output setup
addAnalogOutputChannel(s, 'Dev2', 'ao0', 'Voltage');
Fs = s.Rate;
t1 = 100;
t = 0:1/Fs:t1-1/Fs;
A = 0.5; % Initial magnitude
data0 = A * sin(2 * pi * t * 159.2)';
b = repmat(data0, 5, 1);
queueOutputData(s, b);

% Listener for updating output data with new magnitude
datagiver = addlistener(s, 'DataRequired', @(src, event) updateOutputData(src));

% Start the session in the background
figure(1)
clf
startBackground(s);

% Function to update the output data
function updateOutputData(src)
    newMagnitude = getNewMagnitude(); % This function should provide the updated magnitude
    t = 0:1/src.Rate:1-1/src.Rate; % Generate time vector for one second
    data0 = newMagnitude * sin(2 * pi * t * 159.2)'; % Update data with new magnitude
    b = repmat(data0, 5, 1);
    src.queueOutputData(b);
end

% Function to get a new magnitude value (stub for illustration)
function magnitude = getNewMagnitude()
    % Replace this with your own logic to get the new magnitude
    % For example, reading from a GUI control or an external input
    magnitude = 0.5; % Example fixed value, replace with dynamic logic
end

% Stop the session and close files
s.stop
fclose(fidData);
fclose(fidTime);

I hope this helps!