How to turn real time signal to spectrogram?

I have a code that capture a real time signal from my sensor. The graph was shown in time spectrum, but i want them shown as spectrogram. Do i need to save the graph first, then do the fft and finally plot the fft result to spectrogram? Can I do the fft while i capturing my real time signal and plot the spectrogram?

Heres my code:

clc; clear all;close all;

a= arduino;

ai_pin='A1';

tic;

i=0;

while (toc<4)

      i=i+1;

      t(i)=toc;

      v(i)=readVoltage(a,ai_pin);

      figure(1)
      plot(t,v,'r');
      pause(0.1);
  end

Answer 1

[Walter Roberson]

Your time differences are not going to be exactly consistent, so you cannot do a plain fft or plain spectrogram() call.

Probably your easiest way to proceed is to resample your signals to regular time intervals, followed by calling spectrogram(). See https://www.mathworks.com/help/signal/examples/resampling-nonuniformly-sampled-signals.html

[KwokSing Wong]

When I use the function y = resample(v,115200,44100), it says Undefined function 'resample' for input arguments of type 'double'.

Why is that happening?

[Walter Roberson]

resample is from the signal processing toolbox.