script/tutorial/63_OnlineSpectrumAnalyser.js

@@ -0,0 +1,50 @@
+///////////////////////////////////////////////////////////////////////////////////////////////////
+// Create an online spectrum analyser uysing mathutils.py
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+
+run("mathutils")
+
+function plot_spectrum(signal, sampling_freq){
+	if (!is_defined(plots))    plots = null
+    signal = to_array(signal) 
+    number_of_samples = signal.length
+    time_vector = range(0, number_of_samples, 1).map(function(x) {return x / sampling_freq})  
+    tranform = fft(signal)
+    two_side_spectrum =  get_modulus(tranform).map(function(x) {return x / number_of_samples})    
+    spectrum = two_side_spectrum.slice(1,two_side_spectrum.length/2 + 1).map(function(x) {return x * x})
+    spectrum.splice(0,0,two_side_spectrum[0])    
+    number_of_samples = tranform.length    // Signal may have been padded to next power of two
+    freq_vector = range(0, spectrum.length , 1).map(function(x) {return x * sampling_freq / parseFloat(number_of_samples)})  
+    if (plots == null){
+        plots = plot([signal,spectrum], ["signal", "spectrum"],[time_vector, freq_vector], undefined, title = "Spectrum")
+        plots[0].getAxis(AxisId.Y).setRange(-1.5,2.5)
+        plots[1].getAxis(AxisId.Y).setRange(0.0,1.1)
+    } else {
+        plots[0].getSeries(0).setData(time_vector,signal)
+        plots[1].getSeries(0).setData(freq_vector,spectrum)
+    }
+    return plots
+}    
+
+function get_sample(samples, sampling_freq){
+	return range(0,samples,1).map(function(t) {return Math.sin(200*2*Math.PI*t/sampling_freq) + Math.random()})
+    //Simple example sampling a device:
+    //set_exec_pars(undefined, undefined, undefined, undefined, persist=false)
+    //set_preference(Preference.PLOT_DISABLED, true)
+    //set_preference(Preference.TABLE_DISABLED, true)
+    //return tscan(ai1, samples, 1/sampling_freq).getReadable(0)
+}    
+
+plots = null
+samples = 1024
+sampling_freq = 1024.0
+
+while(true){
+    signal = get_sample(samples, sampling_freq)
+    plots = plot_spectrum(signal, sampling_freq, plots)
+    sleep(0.1)
+    if (plots[0].displayable == false){ 
+        break
+    }
+}