Roy Sandberg / Mbed 2 deprecated BLE_ECG

I've got some basic filter code setup (but not yet tested).

Dependencies:   BLE_API Queue mbed nRF51822

Fork of BLE_HeartRate by Bluetooth Low Energy

noisechk.cpp@62:8e2fbe131b53, 2015-06-28 (annotated)

Committer:
roysandberg
Date:
Sun Jun 28 03:06:00 2015 +0000
Revision:
62:8e2fbe131b53
Working Beat Detection and Analysis

Who changed what in which revision?

UserRevisionLine numberNew contents of line
roysandberg 62:8e2fbe131b53 1 /*****************************************************************************
roysandberg 62:8e2fbe131b53 2 FILE: noisechk.cpp
roysandberg 62:8e2fbe131b53 3 AUTHOR: Patrick S. Hamilton
roysandberg 62:8e2fbe131b53 4 REVISED: 5/13/2002
roysandberg 62:8e2fbe131b53 5 ___________________________________________________________________________
roysandberg 62:8e2fbe131b53 6
roysandberg 62:8e2fbe131b53 7 noisechk.cpp: Noise Check
roysandberg 62:8e2fbe131b53 8 Copywrite (C) 2001 Patrick S. Hamilton
roysandberg 62:8e2fbe131b53 9
roysandberg 62:8e2fbe131b53 10 This file is free software; you can redistribute it and/or modify it under
roysandberg 62:8e2fbe131b53 11 the terms of the GNU Library General Public License as published by the Free
roysandberg 62:8e2fbe131b53 12 Software Foundation; either version 2 of the License, or (at your option) any
roysandberg 62:8e2fbe131b53 13 later version.
roysandberg 62:8e2fbe131b53 14
roysandberg 62:8e2fbe131b53 15 This software is distributed in the hope that it will be useful, but WITHOUT ANY
roysandberg 62:8e2fbe131b53 16 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
roysandberg 62:8e2fbe131b53 17 PARTICULAR PURPOSE. See the GNU Library General Public License for more
roysandberg 62:8e2fbe131b53 18 details.
roysandberg 62:8e2fbe131b53 19
roysandberg 62:8e2fbe131b53 20 You should have received a copy of the GNU Library General Public License along
roysandberg 62:8e2fbe131b53 21 with this library; if not, write to the Free Software Foundation, Inc., 59
roysandberg 62:8e2fbe131b53 22 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
roysandberg 62:8e2fbe131b53 23
roysandberg 62:8e2fbe131b53 24 You may contact the author by e-mail (pat@eplimited.edu) or postal mail
roysandberg 62:8e2fbe131b53 25 (Patrick Hamilton, E.P. Limited, 35 Medford St., Suite 204 Somerville,
roysandberg 62:8e2fbe131b53 26 MA 02143 USA). For updates to this software, please visit our website
roysandberg 62:8e2fbe131b53 27 (http://www.eplimited.com).
roysandberg 62:8e2fbe131b53 28 __________________________________________________________________________
roysandberg 62:8e2fbe131b53 29
roysandberg 62:8e2fbe131b53 30 This file contains functions for evaluating the noise content of a beat.
roysandberg 62:8e2fbe131b53 31
roysandberg 62:8e2fbe131b53 32 *****************************************************************************/
roysandberg 62:8e2fbe131b53 33
roysandberg 62:8e2fbe131b53 34 //#include <stdlib.h>
roysandberg 62:8e2fbe131b53 35 #include <mbed.h>
roysandberg 62:8e2fbe131b53 36 #include "qrsdet.h"
roysandberg 62:8e2fbe131b53 37
roysandberg 62:8e2fbe131b53 38 #define NB_LENGTH MS1500
roysandberg 62:8e2fbe131b53 39 #define NS_LENGTH MS50
roysandberg 62:8e2fbe131b53 40
roysandberg 62:8e2fbe131b53 41 int NoiseBuffer[NB_LENGTH], NBPtr = 0 ;
roysandberg 62:8e2fbe131b53 42 int NoiseEstimate ;
roysandberg 62:8e2fbe131b53 43
roysandberg 62:8e2fbe131b53 44 /************************************************************************
roysandberg 62:8e2fbe131b53 45 GetNoiseEstimate() allows external access the present noise estimate.
roysandberg 62:8e2fbe131b53 46 this function is only used for debugging.
roysandberg 62:8e2fbe131b53 47 *************************************************************************/
roysandberg 62:8e2fbe131b53 48
roysandberg 62:8e2fbe131b53 49 int GetNoiseEstimate()
roysandberg 62:8e2fbe131b53 50 {
roysandberg 62:8e2fbe131b53 51 return(NoiseEstimate) ;
roysandberg 62:8e2fbe131b53 52 }
roysandberg 62:8e2fbe131b53 53
roysandberg 62:8e2fbe131b53 54 /***********************************************************************
roysandberg 62:8e2fbe131b53 55 NoiseCheck() must be called for every sample of data. The data is
roysandberg 62:8e2fbe131b53 56 stored in a circular buffer to facilitate noise analysis. When a
roysandberg 62:8e2fbe131b53 57 beat is detected NoiseCheck() is passed the sample delay since the
roysandberg 62:8e2fbe131b53 58 R-wave of the beat occurred (delay), the RR interval between this
roysandberg 62:8e2fbe131b53 59 beat and the next most recent beat, the estimated offset from the
roysandberg 62:8e2fbe131b53 60 R-wave to the beginning of the beat (beatBegin), and the estimated
roysandberg 62:8e2fbe131b53 61 offset from the R-wave to the end of the beat.
roysandberg 62:8e2fbe131b53 62
roysandberg 62:8e2fbe131b53 63 NoiseCheck() estimates the noise in the beat by the maximum and
roysandberg 62:8e2fbe131b53 64 minimum signal values in either a window from the end of the
roysandberg 62:8e2fbe131b53 65 previous beat to the beginning of the present beat, or a 250 ms
roysandberg 62:8e2fbe131b53 66 window preceding the present beat, which ever is shorter.
roysandberg 62:8e2fbe131b53 67
roysandberg 62:8e2fbe131b53 68 NoiseCheck() returns ratio of the signal variation in the window
roysandberg 62:8e2fbe131b53 69 between beats to the length of the window between the beats. If
roysandberg 62:8e2fbe131b53 70 the heart rate is too high and the beat durations are too long,
roysandberg 62:8e2fbe131b53 71 NoiseCheck() returns 0.
roysandberg 62:8e2fbe131b53 72
roysandberg 62:8e2fbe131b53 73 ***********************************************************************/
roysandberg 62:8e2fbe131b53 74
roysandberg 62:8e2fbe131b53 75 int NoiseCheck(int datum, int delay, int RR, int beatBegin, int beatEnd)
roysandberg 62:8e2fbe131b53 76 {
roysandberg 62:8e2fbe131b53 77 int ptr, i;
roysandberg 62:8e2fbe131b53 78 int ncStart, ncEnd, ncMax, ncMin ;
roysandberg 62:8e2fbe131b53 79 double noiseIndex ;
roysandberg 62:8e2fbe131b53 80
roysandberg 62:8e2fbe131b53 81 NoiseBuffer[NBPtr] = datum ;
roysandberg 62:8e2fbe131b53 82 if(++NBPtr == NB_LENGTH)
roysandberg 62:8e2fbe131b53 83 NBPtr = 0 ;
roysandberg 62:8e2fbe131b53 84
roysandberg 62:8e2fbe131b53 85 // Check for noise in region that is 300 ms following
roysandberg 62:8e2fbe131b53 86 // last R-wave and 250 ms preceding present R-wave.
roysandberg 62:8e2fbe131b53 87
roysandberg 62:8e2fbe131b53 88 ncStart = delay+RR-beatEnd ; // Calculate offset to end of previous beat.
roysandberg 62:8e2fbe131b53 89 ncEnd = delay+beatBegin ; // Calculate offset to beginning of this beat.
roysandberg 62:8e2fbe131b53 90 if(ncStart > ncEnd + MS250)
roysandberg 62:8e2fbe131b53 91 ncStart = ncEnd + MS250 ;
roysandberg 62:8e2fbe131b53 92
roysandberg 62:8e2fbe131b53 93
roysandberg 62:8e2fbe131b53 94 // Estimate noise if delay indicates a beat has been detected,
roysandberg 62:8e2fbe131b53 95 // the delay is not to long for the data buffer, and there is
roysandberg 62:8e2fbe131b53 96 // some space between the end of the last beat and the beginning
roysandberg 62:8e2fbe131b53 97 // of this beat.
roysandberg 62:8e2fbe131b53 98
roysandberg 62:8e2fbe131b53 99 if((delay != 0) && (ncStart < NB_LENGTH) && (ncStart > ncEnd))
roysandberg 62:8e2fbe131b53 100 {
roysandberg 62:8e2fbe131b53 101
roysandberg 62:8e2fbe131b53 102 ptr = NBPtr - ncStart ; // Find index to end of last beat in
roysandberg 62:8e2fbe131b53 103 if(ptr < 0) // the circular buffer.
roysandberg 62:8e2fbe131b53 104 ptr += NB_LENGTH ;
roysandberg 62:8e2fbe131b53 105
roysandberg 62:8e2fbe131b53 106 // Find the maximum and minimum values in the
roysandberg 62:8e2fbe131b53 107 // isoelectric region between beats.
roysandberg 62:8e2fbe131b53 108
roysandberg 62:8e2fbe131b53 109 ncMax = ncMin = NoiseBuffer[ptr] ;
roysandberg 62:8e2fbe131b53 110 for(i = 0; i < ncStart-ncEnd; ++i)
roysandberg 62:8e2fbe131b53 111 {
roysandberg 62:8e2fbe131b53 112 if(NoiseBuffer[ptr] > ncMax)
roysandberg 62:8e2fbe131b53 113 ncMax = NoiseBuffer[ptr] ;
roysandberg 62:8e2fbe131b53 114 else if(NoiseBuffer[ptr] < ncMin)
roysandberg 62:8e2fbe131b53 115 ncMin = NoiseBuffer[ptr] ;
roysandberg 62:8e2fbe131b53 116 if(++ptr == NB_LENGTH)
roysandberg 62:8e2fbe131b53 117 ptr = 0 ;
roysandberg 62:8e2fbe131b53 118 }
roysandberg 62:8e2fbe131b53 119
roysandberg 62:8e2fbe131b53 120 // The noise index is the ratio of the signal variation
roysandberg 62:8e2fbe131b53 121 // over the isoelectric window length, scaled by 10.
roysandberg 62:8e2fbe131b53 122
roysandberg 62:8e2fbe131b53 123 noiseIndex = (ncMax-ncMin) ;
roysandberg 62:8e2fbe131b53 124 noiseIndex /= (ncStart-ncEnd) ;
roysandberg 62:8e2fbe131b53 125 NoiseEstimate = noiseIndex * 10 ;
roysandberg 62:8e2fbe131b53 126 }
roysandberg 62:8e2fbe131b53 127 else
roysandberg 62:8e2fbe131b53 128 NoiseEstimate = 0 ;
roysandberg 62:8e2fbe131b53 129 return(NoiseEstimate) ;
roysandberg 62:8e2fbe131b53 130 }
roysandberg 62:8e2fbe131b53 131