Acquire Data in the Background with Live Plot Updates
This example shows how to acquire data in the background using callbacks while MATLAB continues to run.
A background acquisition uses callbacks to allow your code to access data as the
hardware acquires it or to react to any errors as they occur. In this example, you
acquire data from a microphone with ID
Audio1 using the
ScansAvailableFcnCount property to trigger the function call
defined by the
ScansAvailableFcn property. Using a callback allows
a plot to be updated in real time while acquisition continues.
Get a list of devices so you can identify the microphone you want to use. The partial listing here indicates the device ID.
VendorID DeviceID Description _____________ ________ ________________________________________________________________ "directsound" "Audio1" "DirectSound Headset Microphone (Plantronics BT600)"
directsound DataAcquisition object with a microphone
input channel on
Audio1. You might have to use a different
d = daq("directsound"); ch = addinput(d,"Audio1",1,"audio");
Create a simple callback function to plot the acquired data and save it as
plotMyData.m in your current working folder. Enter the
following code in the file.
function plotMyData(obj,evt) % obj is the DataAcquisition object passed in. evt is not used. data = read(obj,obj.ScansAvailableFcnCount,"OutputFormat","Matrix"); plot(data) end
Set the callback function property of the DataAcquisition object to use your function.
d.ScansAvailableFcn = @plotMyData;
Start the acquisition to run for 5 seconds in the background.
Speak into the microphone and watch the plot. It updates 10 times per second.