File content as of revision 16:503f8308e2db:

/*******************************************************************************
* Copyright (C) 2018 Maxim Integrated Products, Inc., All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
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* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* Except as contained in this notice, the name of Maxim Integrated
* Products, Inc. shall not be used except as stated in the Maxim Integrated
* Products, Inc. Branding Policy.
*
* The mere transfer of this software does not imply any licenses
* of trade secrets, proprietary technology, copyrights, patents,
* trademarks, maskwork rights, or any other form of intellectual
* property whatsoever. Maxim Integrated Products, Inc. retains all
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*******************************************************************************
*/

#include "max30101_algo.h"

//helper functions for the heart rate and SpO2 function
uint16_t avg_dc_est(int32_t *p, uint16_t x);

void lp_dfir_flt(int16_t din0, int16_t din1, int16_t din2, int16_t *dout0, int16_t *dout1, int16_t *dout2) ;
int32_t mul16(int16_t x, int16_t y);

//
//  Heart Rate/SpO2 Monitor function takes sample input 'dinIR' and dinRed.
//  Other inputs:
//      ns -> Sample Counter, increments with each sample input.
//      SampRate -> Input data real-time sample rate.
//      dinLShft -> Number of left shifts for data to be 16 bit wide.
//      compSpO2 -> If '1' compute SpO2 value,else compute HR only.

//
//  Outputs:
//      ir_ac_comp  -> AC component of the IR signal.
//      red_ac_comp -> AC component of the Red signal.
//      ir_ac_mag   -> Peak to Peak magnitude of the IR signal.
//      red_ac_mag  -> Peak to Peak magnitude of the Red signal.
//      HRbpm       -> Heart Rate in beats per minute.
//      SpO2        -> SpO2 value as %saturation.
//      DRdy        -> '1' when new data is available.
//

void HRSpO2Func(uint32_t dinIR, uint32_t dinRed, uint32_t dinGreen, uint32_t ns, uint16_t SampRate, uint16_t compSpO2,
	int16_t *ir_ac_comp, int16_t *red_ac_comp, int16_t *green_ac_comp, int16_t *ir_ac_mag, int16_t *red_ac_mag,
	int16_t *green_ac_mag,    uint16_t *HRbpm2, uint16_t *SpO2B, uint16_t *DRdy)
{
	static int32_t ir_avg_reg = 0;
	static int32_t red_avg_reg = 0;
	static int32_t green_avg_reg = 0;

	static int16_t ir_ac_sig_cur = 0;
	static int16_t ir_ac_sig_min = 0;
	static int16_t ir_ac_sig_max = 0;
	static int16_t ir_avg_est;

	static int16_t ir_pedge = 0, ir_nedge = 0;
	static int16_t ir_pzxic, ir_pzxip;
	static int16_t ir_nzxic;

	static int16_t red_ac_sig_cur = 0;
	static int16_t red_ac_sig_min = 0;
	static int16_t red_ac_sig_max = 0;
	static int16_t red_avg_est;

	static int16_t green_avg_est;
	static int16_t green_ac_sig_cur = 0;
	//static int16_t green_ac_sig_cur=0;
	static int16_t green_ac_sig_pre;
	static int16_t green_ac_sig_max ;
	static int16_t  green_ac_sig_min;
	static int16_t green_mac_FIFO[5];
	int16_t meanGreenMagFIFO;
	int16_t minAmpForHeartBeat ;

	uint32_t  IRData, RedData, greenData, rnum, rden, rdens;
	uint16_t  zeros_in_HrQue = 0, posCount = 0;
	static uint32_t prevPeakLoc = 0;
	static int16_t IrFIFO[100];
	static int16_t HrQue[10], lastKnownGoodHr[10];
	static int16_t SPO2Que[5];
	int16_t SPO2score[5];
	static uint16_t HrQindex = 0, lengthOfposCountExceeding = 0;
	static uint16_t initHrQueCounter = 0, fingerOff = 0;

	static int16_t HrQueSmoothing[3];
	static int16_t SPO2QueSmoothing[3];

	int16_t  k, j;
	uint32_t peakLoc ;
	int16_t bufferIdx1,  bufferIdx2;
	int16_t maxFIFO, IdxMaxFIFO ;
	int16_t HRperiod2, HRComp2, deltaHR;
	int16_t cSpO2 = 0, SpO2;

	int16_t HrCount = 0, HrSum = 0, meanGreenMagFIFOcounter = 0;
	int16_t SPO2D = 0, meanHrQ;
	int16_t dx[99], cumsumX[99];
	static int16_t SPO2QueCounter = 0 ; //, lastDisplayedHrValue;

	int16_t validSPO2Count = 0;
	int16_t validSPO2Sum = 0;
	int16_t SPO2scoreAverage =  0;
	int16_t SPO2scoreSum = 0 ;
	// int16_t deltaMeanLastKnownGoodHr = 0, meanLastKnownGoodHr = 0;
	// int16_t counterMeanLastKnownGoodHr = 0;


	/* clear some vars if fresh new start */
	if ((ns == 0) || (fingerOff > 300)) {
		ir_avg_reg = 0;
		red_avg_reg = 0;
		green_avg_reg = 0;

		ir_ac_sig_cur = 0;
		ir_ac_sig_min = 0;
		ir_ac_sig_max = 0;

		ir_avg_est = 0;
		green_avg_est = 0;
		red_avg_est = 0 ;

		ir_pedge = 0;
		ir_nedge = 0;
		ir_pzxic = 0;
		ir_pzxip = 0;
		ir_nzxic = 0 ;
		//ir_nzxip = 0;
		red_ac_sig_cur = 0;
		red_ac_sig_min = 0;
		red_ac_sig_max = 0;

		prevPeakLoc = 0 ;
		bufferIdx1 = 0 ;
		bufferIdx2 = 0;
		HrQindex = 0;
		initHrQueCounter = 0;
		lengthOfposCountExceeding = 0 ;
		fingerOff = 0;
		HRComp2 = 0;

		for (k = 0 ; k < 100 ; k++) {
			IrFIFO[k] = 0;
		}

		for (k = 0 ; k < 10 ; k++) {
			HrQue[k] = 0;
			lastKnownGoodHr[k] = 0;
		}

		for (k = 0 ; k < 3 ; k++) {
			HrQueSmoothing[k] = 70;
			SPO2QueSmoothing[k] = 97;
		}

		for (k = 0 ; k < 5 ; k++) {
			SPO2Que[k] = 97;
			SPO2score[k] = 0;
			green_mac_FIFO[k] = 0;
		}

		SPO2QueCounter = 0;
		*SpO2B = 97;
		*HRbpm2 = 0;
		*DRdy = 0 ;
	}


	/* Save current state */
	green_ac_sig_pre = green_ac_sig_cur;

	/* Process next data sample */
	minAmpForHeartBeat = 0;
	IRData  = dinIR;
	RedData = dinRed;
	greenData = dinGreen ;

	ir_avg_est  = avg_dc_est(&ir_avg_reg, IRData);
	red_avg_est = avg_dc_est(&red_avg_reg, RedData);
	green_avg_est = avg_dc_est(&green_avg_reg, greenData);

	lp_dfir_flt((uint16_t)(IRData - ir_avg_est), (uint16_t)(RedData - red_avg_est),
		(uint16_t)(greenData - green_avg_est),  &ir_ac_sig_cur, &red_ac_sig_cur, &green_ac_sig_cur);

	*ir_ac_comp = ir_ac_sig_cur;
	*red_ac_comp = red_ac_sig_cur;
	*green_ac_comp = green_ac_sig_cur;

	/* save to FIFO */
	for (k = 1 ; k < 100 ; k++) {
		IrFIFO[100 - k] = IrFIFO[99 - k];
	}
	IrFIFO[0] =  green_ac_sig_cur ; // invert
	for (k = 0 ; k < 97 ; k++) {
		dx[k] = IrFIFO[k + 2] - IrFIFO[k] ;
	}
	dx[97] = dx[96];
	dx[98] = dx[96];

	for (k = 0 ; k < 99 ; k++) {
		if (dx[k] > 0) {
			dx[k] = 1;
		} else {
			dx[k] = 0;
		}
	}

	cumsumX[0] = 0;
	for (k = 1; k < 99 ; k++) {
		if (dx[k] > 0) {
			cumsumX[k] =  cumsumX[k - 1] + dx[k] ;
		} else {
			cumsumX[k] =  0;
		}
	}

	/* determine noise
	 * ignore less than 3 consecutive non-zeros's
	 * detect # of sign change
	 */
	posCount = 0;
	for (k = 1; k < 99 ; k++) {
		if (cumsumX[k] > 0) {
			posCount ++ ;
		} else if (cumsumX[k] == 0) {
			if (posCount < 4  && k >= 4) {
				for (j = k - 1; j > k - posCount - 1; j--) {
					cumsumX[j] = 0 ;
				}
			}
			posCount = 0;
		}
	}

	/* ignore less than 3 consecutive zeros's */
	posCount = 0;
	for (k = 1; k < 99 ; k++) {
		if (cumsumX[k] == 0) {
			posCount ++ ;
		} else if (cumsumX[k] > 0) {
			if (posCount < 4  && k >= 4) {
				for (j = k - 1; j > k - posCount - 1; j--) {
					cumsumX[j] = 100 ;
				}
			}
			posCount = 0;
		}
	}

	/* detect # of sign change */
	posCount = 0; /* sign change counter */
	for (k = 0; k < 98 ; k++) {
		if (cumsumX[k] == 0  && cumsumX[k + 1] > 0) {
			posCount ++;
		}
	}
	if (posCount >= 4) {
		lengthOfposCountExceeding ++ ;
	} else {
		lengthOfposCountExceeding = 0 ;
	}

	/*  Detect IR channel positive zero crossing (rising edge) */
	if ((green_ac_sig_pre < 0) && (green_ac_sig_cur >= 0) && fingerOff == 0) {
		*ir_ac_mag = ir_ac_sig_max - ir_ac_sig_min;
		*red_ac_mag = red_ac_sig_max - red_ac_sig_min;
		*green_ac_mag = green_ac_sig_max - green_ac_sig_min;
		if (*green_ac_mag > 0) {
			for (k = 0; k < 4 ; k++) {
				green_mac_FIFO[k] = green_mac_FIFO[k + 1];
			}
			green_mac_FIFO[4] = *green_ac_mag ;
			if (green_mac_FIFO[4] > 1000) {
				green_mac_FIFO[4] = 1000;
			}
		}
		meanGreenMagFIFO = 0;
		meanGreenMagFIFOcounter = 0;
		for (k = 0; k < 5 ; k++) {
			if (green_mac_FIFO[k] > 0) {
				meanGreenMagFIFO = meanGreenMagFIFO + green_mac_FIFO[k] ;
				meanGreenMagFIFOcounter++;
			}
		}
		if (meanGreenMagFIFOcounter >= 2) {
			meanGreenMagFIFO = meanGreenMagFIFO / meanGreenMagFIFOcounter ;
			minAmpForHeartBeat = meanGreenMagFIFO / 4 ; //25% of mean of past heart beat
		} else {
			minAmpForHeartBeat = 75;
		}
		if (minAmpForHeartBeat < 75) {
			minAmpForHeartBeat = 75;
		}
		if (minAmpForHeartBeat > 400) {
			minAmpForHeartBeat = 400;
		}

		ir_pedge = 1;
		ir_nedge = 0;
		ir_ac_sig_max = 0;
		ir_pzxip = ir_pzxic;
		ir_pzxic = ns;
		bufferIdx1 = ir_pzxic - ir_nzxic;
		bufferIdx2 = ir_pzxic - ir_pzxip;

		if ((*green_ac_mag) > minAmpForHeartBeat && (*green_ac_mag) < 20000 && bufferIdx1 >= 0
			&& bufferIdx1 < 100 && bufferIdx2 >= 0 && bufferIdx2 < 100 && bufferIdx1 < bufferIdx2) { // was <5000
			maxFIFO = -32766;

			IdxMaxFIFO = 0;
			for (j = bufferIdx1; j <= bufferIdx2; j++) { // find max peak
				if (IrFIFO[j] > maxFIFO) {
					maxFIFO = IrFIFO[j];
					IdxMaxFIFO  = j;
				}
			}
			peakLoc = ir_pzxic - IdxMaxFIFO + 1 ;

			if (prevPeakLoc != 0) {
				HRperiod2 = (uint16_t)(peakLoc -  prevPeakLoc);
				if (HRperiod2 > 33 && HRperiod2 < 134) {
					HRComp2 = (6000 / HRperiod2);
					fingerOff = 0 ;
				} else {
					HRComp2 = 0 ;
				}
			} else {
				HRComp2 = 0 ;
			}

			if (initHrQueCounter < 10  && HRComp2 > 0) {
				HrQue[HrQindex] = HRComp2;
				HrQindex++;
				initHrQueCounter ++;
				if (HrQindex == 10) {
					HrQindex  = 0;
				}
			}

			if (initHrQueCounter > 7 && lengthOfposCountExceeding <= 3) {
				if (HRComp2 > 0) {

					HrCount = 0;
					HrSum = 0;
					zeros_in_HrQue = 0;
					for (k = 1 ; k < initHrQueCounter ; k++) {
						if (HrQue[k] > 0) {
							HrSum += HrQue[k];
							HrCount ++;
						} else {
							zeros_in_HrQue ++;
						}
					}
					meanHrQ = HrSum / HrCount ;
					deltaHR = lastKnownGoodHr[0] / 10;

					if (HRComp2 >  lastKnownGoodHr[0] - deltaHR &&  HRComp2  < lastKnownGoodHr[0] + deltaHR) {
						for (k = 1 ; k < 10 ; k++) {
							HrQue[10 - k] = HrQue[9 - k];
						}
						HrQue[0] = HRComp2;
					} /* HR smoothing using FIFO queue */

					if (zeros_in_HrQue <= 2) {
						for (k = 1 ; k < 3 ; k++) {
							HrQueSmoothing[3 - k] = HrQueSmoothing[2 - k];
						}
						HrQueSmoothing[0] = meanHrQ ;
						HRComp2 = ((HrQueSmoothing[0] << 2) + (HrQueSmoothing[1] << 1) + (HrQueSmoothing[2] << 1)) >> 3;
						*HRbpm2 = HRComp2 ;

						for (k = 1 ; k < 10 ; k++) {
							lastKnownGoodHr[10 - k] = lastKnownGoodHr[9 - k];
						}
						lastKnownGoodHr[0] = HRComp2;
					}
				}

			} else if (initHrQueCounter < 7) { /* before que is filled up, display whatever it got. */
				*HRbpm2 =  HRComp2;

			} else {
				//  *HRbpm2 =  0 ;
				HrCount = 0;
				HrSum = 0;
				for (k = 0 ; k < 10 ; k++) {
					if (lastKnownGoodHr[k] > 0) {
						HrSum = HrSum + lastKnownGoodHr[k];
						HrCount++;
					}
				}
				if (HrCount > 0) {
					*HRbpm2 = HrSum / HrCount;
				} else {
					*HRbpm2 = 0;
				}
			}
			prevPeakLoc = peakLoc ; /* save peakLoc into Static var */

			if (compSpO2) {
				rnum = (ir_avg_reg >> 20) * (*red_ac_mag);
				rden = (red_avg_reg >> 20) * (*ir_ac_mag);
				rdens = (rden >> 15);
				if (rdens > 0) {
					cSpO2 = 110 - (((25 * rnum) / (rdens)) >> 15);
				}

				if (cSpO2 >= 100) {
					SpO2 = 100;
				} else if (cSpO2 <= 70) {
					SpO2 = 70;
				} else {
					SpO2 = cSpO2;
				}

				SPO2Que[SPO2QueCounter ] = SpO2;

				for (k = 0 ; k < 5 ; k++) {
					SPO2score[k] = 0;
					for (j = 0 ; j < 5 ; j++)
						if (abs(SPO2Que[k] - SPO2Que[j]) > 5) {
							SPO2score[k] ++;
						}
				}

				SPO2scoreSum =  0;
				for (k = 0 ; k < 5 ; k++) {
					SPO2scoreSum += SPO2score[k] ;
				}
				SPO2scoreAverage = SPO2scoreSum / 5;
				for (k = 1 ; k < 5 ; k++) {
					SPO2score[k] = SPO2score[k] - SPO2scoreAverage;
				}

				validSPO2Count = 0;
				validSPO2Sum = 0;
				for (k = 1 ; k < 5 ; k++) {
					if (SPO2score[k] <= 0) { // add for HR to report
						validSPO2Sum += SPO2Que[k];
						validSPO2Count ++;
					}
				}
				if (validSPO2Count > 0) {
					SPO2D = (validSPO2Sum / validSPO2Count) - 1;
				}
				if (SPO2D > 100) {
					SPO2D = 100;
				}

				SPO2QueCounter ++;
				if (SPO2QueCounter == 5) {
					SPO2QueCounter = 0;
				}

				for (k = 1 ; k < 3 ; k++) {
					SPO2QueSmoothing[3 - k] = SPO2QueSmoothing[2 - k];
				}
				SPO2QueSmoothing[0] = SPO2D;
				*SpO2B = ((SPO2QueSmoothing[0] << 2) + (SPO2QueSmoothing[1] << 1) + (SPO2QueSmoothing[2] << 1)) >> 3;

				if (*SpO2B > 100) {
					*SpO2B = 100 ;
				}

			} else {
				SpO2 = 0;
				*SpO2B = 0;
			}
			*DRdy = 1;

		}
	}

	/* Detect IR channel negative zero crossing (falling edge) */
	if ((green_ac_sig_pre > 0) && (green_ac_sig_cur <= 0)) {
		ir_pedge = 0;
		ir_nedge = 1;
		ir_ac_sig_min = 0;
		ir_nzxic = ns;
	}

	/* Find Maximum IR & Red values in positive cycle */
	if (ir_pedge && (green_ac_sig_cur > green_ac_sig_pre)) {
		ir_ac_sig_max  = ir_ac_sig_cur;
		red_ac_sig_max = red_ac_sig_cur;
		green_ac_sig_max = green_ac_sig_cur;
	}

	/* Find minimum IR & Red values in negative cycle */
	if (ir_nedge && (green_ac_sig_cur < green_ac_sig_pre)) {
		ir_ac_sig_min  = ir_ac_sig_cur;
		red_ac_sig_min = red_ac_sig_cur;
		green_ac_sig_min = green_ac_sig_cur;
	}

	if (IRData < 50000) {
		// finger-off
		fingerOff++;
		*DRdy = 0;
	} else {
		fingerOff = 0 ;
	}

	if (*SpO2B ==  0  ||   *HRbpm2 == 0) {
		*DRdy = 0;
	}
}

/*
 * Average DC Estimator
 */
uint16_t avg_dc_est(int32_t *p, uint16_t x)
{
	*p += ((((int32_t) x << 15) - *p) >> 4);
	return (*p >> 15);
}

/*
 * Symmetric Dual Low Pass FIR Filter
 */
void lp_dfir_flt(int16_t din0, int16_t din1, int16_t din2, int16_t *dout0, int16_t *dout1, int16_t *dout2)
{
	static const uint16_t FIRCoeffs[12] = {688, 1283, 2316, 3709, 5439, 7431,
			9561, 11666, 13563, 15074, 16047, 16384
		};

	static int16_t cbuf0[32], cbuf1[32], cbuf2[32];
	static int16_t offset = 0;
	int32_t y0, y1, y2;
	int16_t i;

	cbuf0[offset] = din0;
	cbuf1[offset] = din1;
	cbuf2[offset] = din2;

	y0 = mul16(FIRCoeffs[11], cbuf0[(offset - 11) & 0x1F]);
	y1 = mul16(FIRCoeffs[11], cbuf1[(offset - 11) & 0x1F]);
	y2 = mul16(FIRCoeffs[11], cbuf2[(offset - 11) & 0x1F]);


	for (i = 0; i < 11; i++) {
		y0 += mul16(FIRCoeffs[i], cbuf0[(offset - i) & 0x1F] + cbuf0[(offset - 22 + i) & 0x1F]);
		y1 += mul16(FIRCoeffs[i], cbuf1[(offset - i) & 0x1F] + cbuf1[(offset - 22 + i) & 0x1F]);
		y2 += mul16(FIRCoeffs[i], cbuf2[(offset - i) & 0x1F] + cbuf2[(offset - 22 + i) & 0x1F]);
	}
	offset = (offset + 1) & 0x1F;

	*dout0 = (y0 >> 15);
	*dout1 = (y1 >> 15);
	*dout2 = (y2 >> 15);
}

/*
 * Integer multiplier
 */
int32_t mul16(int16_t x, int16_t y)
{
	return (int32_t)(x * y);
}