Diff: MAX30100_SpO2Calculator.cpp

Revision:

0:010b908e2187

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MAX30100_SpO2Calculator.cpp	Fri Nov 25 00:52:54 2016 +0000
@@ -0,0 +1,71 @@
+/*
+Arduino-MAX30100 oximetry / heart rate integrated sensor library
+Copyright (C) 2016  OXullo Intersecans <x@brainrapers.org>
+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/>.
+*/
+
+#include <math.h>
+
+#include "MAX30100_SpO2Calculator.h"
+
+// SaO2 Look-up Table
+// http://www.ti.com/lit/an/slaa274b/slaa274b.pdf
+const uint8_t SpO2Calculator::spO2LUT[43] = {100,100,100,100,99,99,99,99,99,99,98,98,98,98,
+                                             98,97,97,97,97,97,97,96,96,96,96,96,96,95,95,
+                                             95,95,95,95,94,94,94,94,94,93,93,93,93,93};
+
+SpO2Calculator::SpO2Calculator() :
+    irACValueSqSum(0),
+    redACValueSqSum(0),
+    beatsDetectedNum(0),
+    samplesRecorded(0),
+    spO2(0)
+{
+}
+
+void SpO2Calculator::update(float irACValue, float redACValue, bool beatDetected)
+{
+    irACValueSqSum += irACValue * irACValue;
+    redACValueSqSum += redACValue * redACValue;
+    ++samplesRecorded;
+
+    if (beatDetected) {
+        ++beatsDetectedNum;
+        if (beatsDetectedNum == CALCULATE_EVERY_N_BEATS) {
+            float acSqRatio = 100.0 * log(redACValueSqSum/samplesRecorded) / log(irACValueSqSum/samplesRecorded);
+            uint8_t index = 0;
+
+            if (acSqRatio > 66) {
+                index = (uint8_t)acSqRatio - 66;
+            } else if (acSqRatio > 50) {
+                index = (uint8_t)acSqRatio - 50;
+            }
+            reset();
+
+            spO2 = spO2LUT[index];
+        }
+    }
+}
+
+void SpO2Calculator::reset()
+{
+    samplesRecorded = 0;
+    redACValueSqSum = 0;
+    irACValueSqSum = 0;
+    beatsDetectedNum = 0;
+    spO2 = 0;
+}
+
+uint8_t SpO2Calculator::getSpO2()
+{
+    return spO2;
+}
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