How do I plot live data acquired via a NIDAQ inside a GUI window?
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I currently have a function which plots data acquired via a NIDAQ (NI USB-6218) in real time. This is the following function, "acquirelive" :
% acquirelive function:
% acquire signal in real time
global time;
global data;
s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev1', 0, 'Voltage');
s.Rate = 1000;
s.DurationInSeconds = 10;
lh = addlistener(s,'DataAvailable', @collectData);
s.startBackground();
This function calls the collectData function, which is the following:
function collectData(s,event)
time = event.TimeStamps;
data = event.Data;
h = animatedline(time,data);
end
This works well and plots the data in real-time over a 10 second period. However, when I attach this "acquirelive" function to a button in a GUI I'm designing using GUIDE, the GUI opens but nothing happens when the plot button is clicked (inside or outside the GUI). There is also no error message generated. This is the code associated with the button in the GUI:
function PlotButton_Callback(hObject, eventdata, handles)
acquirelive;
The GUI is pretty simple. There are no buttons aside from the plot button (it looks like this):
Any ideas why the placement of the function inside the GUI causes this problem? Do I need to initialize the axes of the plot in the code at some point?
Thanks for any advice you might have, I appreciate it! Let me know if more information is needed to answer the question.
2 Comments
Geoff Hayes
on 6 Jul 2016
Eamon - you may want to put a breakpoint at the line where you call acquirelive from the pushbutton callback so that when you press the button, you can start stepping through the code within the acquirelive script. When you do so, check to see if all variables are initialized properly.
If all code seems to be getting initialized proper but still nothing happens, then try copying and pasting the code from this script into your pushbutton callback (less the global variables since they seem to be unused). Or better yet, save the s to the handles structure so that you don't "lose" it and can access it again (to perhaps stop the data acquisition). Something like
function PlotButton_Callback(hObject, eventdata, handles)
handles.s = daq.createSession('ni');
addAnalogInputChannel(handles.s,'Dev1', 0, 'Voltage');
handles.s.Rate = 1000;
handles.s.DurationInSeconds = 10;
lh = addlistener(handles.s,'DataAvailable', @collectData);
handles.s.startBackground();
guidata(hObject, handles); % to save the updated handles structure
Does the above make a difference?
Accepted Answer
More Answers (1)
Geoff Hayes
on 6 Jul 2016
Edited: Walter Roberson
on 9 Jul 2016
Eamon - animatedline allows you to specify which axes you wish to create the line in, so you will need to pass the handle to your axes into the collectData callback. If the Tag property for your axes is axes1, then I think that you can do something like
...
lh = addlistener(handles.s,'DataAvailable', {@collectData,handles.axes1});
...
In the above, we just pass the axes handles as an input to the collectData function. This function will then change to
function collectData(s,event,hAxes)
time = event.TimeStamps;
data = event.Data;
h = animatedline(hAxes,time,data);
end
That should work. One thing you may want to consider is the line
h = animatedline(hAxes,time,data);
With it, you will be creating a new graphics object each time. This may be a problem depending upon often you are creating a line (does the rate refer to how many times a second or..?). An alternative is to create one animated line and just update its data over time. See the examples from the documentation and how the function addpoints is used.
16 Comments
Geoff Hayes
on 8 Jul 2016
Eamon - hmmm...perhaps you can't add additional parameters to this callback. The alternative is to have the collectData function "look" for your GUI and grab the handle to the axes from it. If the Tag property for your GUI is set to (say) myGUI and its HandleVisibility property to on, then in your collectData callback you would do
function collectData(s,event,hAxes)
time = event.TimeStamps;
data = event.Data;
hGui = findobj('Tag','myGUI');
if ~isempty(hGUI)
handles = guidata(hGui);
if isfield(handles,'axes1')
h=animatedline(handles.axes1,time,data);
end
end
end
The problem with the above is that it ties your callback to the GUI which was why the other option was preferred since we just pass in a handle to an axes.
Eamon
on 8 Jul 2016
Geoff Hayes
on 9 Jul 2016
Hi Eamon - can you verify that the value for
hGui = findobj('Tag','optogui');
is in fact the handle to your GUI? For example, does hGui equal the handles.optogui?
Walter Roberson
on 9 Jul 2016
One possibility is that you might be getting multiple objects returned.
Another possibility is that 'optogui' is the tag for a hidden handle and you need findall instead of findobj.
Geoff Hayes
on 10 Jul 2016
Eamon - what version of MATLAB are you using? I'm using R2014a and the above description for h is foreign to me. Are you using a later version?
Eamon
on 10 Jul 2016
Geoff Hayes
on 11 Jul 2016
Eamon - what happens if you type
get(hGui)
What are the properties that it returns? But the above, it seems like this is a figure so I'm not sure why you are observing that error.
I can simulate this error message if the GUI is closed before I call guidata.
Geoff Hayes
on 11 Jul 2016
Eamon - you have to do this from the collectData function where hGui is defined.
Eamon
on 11 Jul 2016
Geoff Hayes
on 13 Jul 2016
Eamon - I'm not sure why your guidata call does not work. You would probably need to attach some of your code so that we can see how all of this works together. Alternatively, you could try using findobj to get the axes from your figure (assuming that there is just the one axes)
findobj('Parent',h,'-and','Type','axes')
Again, the HandleVisibility property for your figure would need to be on.
Geoff Hayes
on 14 Jul 2016
Eamon - I would put a breakpoint at the line
h=animatedline(handles.axes1,time,data);
and then run your GUI. When the debugger pauses at this line, check to see what is handles.axes1, time and data. It could be that the error message is referring to the time array. Check the type of each using
class(time)
class(data)
Perhaps the time array (which is the x input to animatedline and must be of type double) is an (say) integer array instead.
Eamon
on 19 Jul 2016
Noah Prisament
on 7 Jun 2023
This error:
Error using animatedline
Invalid type for argument X. Type should be double.
was most likely caused by non-double-typed data being sent to the "animatedline" initializer. The AnimatedLine previously only supported double-typed data for all axes. Now in R2023a, the AnimatedLine supports all numeric datatypes as well as datetimes and durations for all axes. Therefore, this error should not occur in the newest version of MATLAB.
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