Refactored Ppg for frequency based algorithm. (#1486)

New implementation of the heart rate sensor data processing using a frequency based PPG algorithm.
The HRS3300 settings are fine-tuned for better signal to noise at 10Hz.
The measurement delay is now set to 100ms.
Enable and use the ambient light sensor.
FFT implementation based on ArduinoFFT (https://github.com/kosme/arduinoFFT, GPLv3.0).

1 files changed, 129 insertions, 0 deletions

diff --git a/src/libs/arduinoFFT-develop/Examples/FFT_speedup/FFT_speedup.ino b/src/libs/arduinoFFT-develop/Examples/FFT_speedup/FFT_speedup.ino
new file mode 100644
index 00000000..a059a170
--- /dev/null
+++ b/src/libs/arduinoFFT-develop/Examples/FFT_speedup/FFT_speedup.ino
@@ -0,0 +1,129 @@
+/*
+
+	Example of use of the FFT libray to compute FFT for a signal sampled through the ADC
+    with speedup through different arduinoFFT options. Based on examples/FFT_03/FFT_03.ino
+  
+    Copyright (C) 2020 Bim Overbohm (header-only, template, speed improvements)
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+// There are two speedup options for some of the FFT code:
+
+// Define this to use reciprocal multiplication for division and some more speedups that might decrease precision
+//#define FFT_SPEED_OVER_PRECISION
+
+// Define this to use a low-precision square root approximation instead of the regular sqrt() call
+// This might only work for specific use cases, but is significantly faster. Only works for ArduinoFFT<float>.
+//#define FFT_SQRT_APPROXIMATION
+
+#include "arduinoFFT.h"
+
+/*
+These values can be changed in order to evaluate the functions
+*/
+#define CHANNEL A0
+const uint16_t samples = 64; //This value MUST ALWAYS be a power of 2
+const float samplingFrequency = 100; //Hz, must be less than 10000 due to ADC
+unsigned int sampling_period_us;
+unsigned long microseconds;
+
+/*
+These are the input and output vectors
+Input vectors receive computed results from FFT
+*/
+float vReal[samples];
+float vImag[samples];
+
+/*
+Allocate space for FFT window weighing factors, so they are calculated only the first time windowing() is called.
+If you don't do this, a lot of calculations are necessary, depending on the window function.
+*/
+float weighingFactors[samples];
+
+/* Create FFT object with weighing factor storage */
+ArduinoFFT<float> FFT = ArduinoFFT<float>(vReal, vImag, samples, samplingFrequency, weighingFactors);
+
+#define SCL_INDEX 0x00
+#define SCL_TIME 0x01
+#define SCL_FREQUENCY 0x02
+#define SCL_PLOT 0x03
+
+void setup()
+{
+  sampling_period_us = round(1000000*(1.0/samplingFrequency));
+  Serial.begin(115200);
+  Serial.println("Ready");
+}
+
+void loop()
+{
+  /*SAMPLING*/
+  microseconds = micros();
+  for(int i=0; i<samples; i++)
+  {
+      vReal[i] = analogRead(CHANNEL);
+      vImag[i] = 0;
+      while(micros() - microseconds < sampling_period_us){
+        //empty loop
+      }
+      microseconds += sampling_period_us;
+  }
+  /* Print the results of the sampling according to time */
+  Serial.println("Data:");
+  PrintVector(vReal, samples, SCL_TIME);
+  FFT.windowing(FFTWindow::Hamming, FFTDirection::Forward);	/* Weigh data */
+  Serial.println("Weighed data:");
+  PrintVector(vReal, samples, SCL_TIME);
+  FFT.compute(FFTDirection::Forward); /* Compute FFT */
+  Serial.println("Computed Real values:");
+  PrintVector(vReal, samples, SCL_INDEX);
+  Serial.println("Computed Imaginary values:");
+  PrintVector(vImag, samples, SCL_INDEX);
+  FFT.complexToMagnitude(); /* Compute magnitudes */
+  Serial.println("Computed magnitudes:");
+  PrintVector(vReal, (samples >> 1), SCL_FREQUENCY);
+  float x = FFT.majorPeak();
+  Serial.println(x, 6); //Print out what frequency is the most dominant.
+  while(1); /* Run Once */
+  // delay(2000); /* Repeat after delay */
+}
+
+void PrintVector(float *vData, uint16_t bufferSize, uint8_t scaleType)
+{
+  for (uint16_t i = 0; i < bufferSize; i++)
+  {
+    float abscissa;
+    /* Print abscissa value */
+    switch (scaleType)
+    {
+      case SCL_INDEX:
+        abscissa = (i * 1.0);
+	break;
+      case SCL_TIME:
+        abscissa = ((i * 1.0) / samplingFrequency);
+	break;
+      case SCL_FREQUENCY:
+        abscissa = ((i * 1.0 * samplingFrequency) / samples);
+	break;
+    }
+    Serial.print(abscissa, 6);
+    if(scaleType==SCL_FREQUENCY)
+      Serial.print("Hz");
+    Serial.print(" ");
+    Serial.println(vData[i], 4);
+  }
+  Serial.println();
+}