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/*
SPDX-License-Identifier: LGPL-3.0-or-later
Original work Copyright (C) 2020 Daniel Thompson
C++ port Copyright (C) 2021 Jean-François Milants
*/
#include "components/heartrate/Ppg.h"
#include <vector>
#include <nrf_log.h>
using namespace Pinetime::Controllers;
/** Original implementation from wasp-os : https://github.com/daniel-thompson/wasp-os/blob/master/wasp/ppg.py */
namespace {
int Compare(int8_t* d1, int8_t* d2, size_t count) {
int e = 0;
for (size_t i = 0; i < count; i++) {
auto d = d1[i] - d2[i];
e += d * d;
}
return e;
}
int CompareShift(int8_t* d, int shift, size_t count) {
return Compare(d + shift, d, count - shift);
}
int Trough(int8_t* d, size_t size, uint8_t mn, uint8_t mx) {
auto z2 = CompareShift(d, mn - 2, size);
auto z1 = CompareShift(d, mn - 1, size);
for (int i = mn; i < mx + 1; i++) {
auto z = CompareShift(d, i, size);
if (z2 > z1 && z1 < z) {
return i;
}
z2 = z1;
z1 = z;
}
return -1;
}
}
Ppg::Ppg()
: hpf {0.87033078, -1.74066156, 0.87033078, -1.72377617, 0.75754694},
agc {20, 0.971, 2},
lpf {0.11595249, 0.23190498, 0.11595249, -0.72168143, 0.18549138} {
}
int8_t Ppg::Preprocess(float spl) {
spl -= offset;
spl = hpf.Step(spl);
spl = agc.Step(spl);
spl = lpf.Step(spl);
auto spl_int = static_cast<int8_t>(spl);
if (dataIndex < 200) {
data[dataIndex++] = spl_int;
}
return spl_int;
}
int Ppg::HeartRate() {
if (dataIndex < 200) {
return 0;
}
NRF_LOG_INFO("PREPROCESS, offset = %d", offset);
auto hr = ProcessHeartRate();
dataIndex = 0;
return hr;
}
int Ppg::ProcessHeartRate() {
int t0 = Trough(data.data(), dataIndex, 7, 48);
if (t0 < 0) {
return 0;
}
int t1 = t0 * 2;
t1 = Trough(data.data(), dataIndex, t1 - 5, t1 + 5);
if (t1 < 0) {
return 0;
}
int t2 = (t1 * 3) / 2;
t2 = Trough(data.data(), dataIndex, t2 - 5, t2 + 5);
if (t2 < 0) {
return 0;
}
int t3 = (t2 * 4) / 3;
t3 = Trough(data.data(), dataIndex, t3 - 4, t3 + 4);
if (t3 < 0) {
return (60 * 24 * 3) / t2;
}
return (60 * 24 * 4) / t3;
}
void Ppg::SetOffset(uint16_t offset) {
this->offset = offset;
dataIndex = 0;
}
void Ppg::Reset() {
dataIndex = 0;
}
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