/* * File: Blood Pressure Calculation Using NIRS * Authors: Michelle Felizardo, Hannah Gallovic * Adapted from: * TFT_ADC_read.c by * Author: Bruce Land * Target PIC: PIC32MX250F128B */ //////////////////////////////////// // clock and protothreads configuration #include "config.h" // threading library #include "pt_cornell_1_2.h" //////////////////////////////////// // graphics libraries #include "tft_master.h" #include "tft_gfx.h" #include #include //////////////////////////////////// // string buffer for TFT display char buffer[60]; // === thread structures ============================================ // thread control structs static struct pt pt_adc, pt_calc ; // === variable initializations ===================================== //num samples = fs * sampling time #define num_samps 50 static float data5[num_samps]; //save each ADC read from channel 5 (AN5) to array static float data11[num_samps]; //save each ADC read from channel 11 (AN11) to array //iteration variables static int i = 0; static int j, k, m, n, z; static float max5, min5, max11, min11, midpnt5, midpnt11; //max, min, and midpoint voltage values for AN5 and AN11 static signed int max5ind, min5ind, max11ind, min11ind; //vector indices of max, min voltage values static signed int midpnt5ind, midpnt11ind; //vector indices of midpoint indices static float lag_sec; //time in seconds between pulse wave arrivals at bicep and at finger tip static float lag_sec_vect[50]; //array to keep track of lag for 50 samples static int lag_ind = 0; //iteration variable in calculating average lag float avg_lag_sec = 0.0; //initialize average lag as 0 float sum; //for calculating average lag static int channel5, channel11; //for reading in ADC samples from AN5 and AN11 static float V5, V11; //for converting from 0 to 1023 to 0 to 3.3V static float C = 8.2007; //constant used in BP calculation (calibrated to test subject) static float arm_dist = 0.508; //distance between two measurement points (in meters) (specific to test subject) static float BP = 0.0; //initialize blood pressure as 0 //============================================================================================================// /* Blood Pressure Calculation Thread When the samples have finished being collected and saved to data5 and data11 vectors (determined by defining num_samps variable above), spawn this thread and use data to perform calculations to determine systolic blood pressure */ static PT_THREAD (protothread_calc_vel(struct pt *pt)){ PT_BEGIN(pt); //iterate through data vectors to find the max and min voltage values; also save their indices //(min and max initialized as 3.3V and 0.0V respectively, in main) //AN5: for(j=0;j max5){ //if current data5 value is greater than current max5, set max5 to current data5 value max5 = data5[j]; max5ind = j; //save index } else if(data5[j] <= min5){ //if current data5 value is less than or equal to than current min5, set min5 to current data5 value min5 = data5[j]; min5ind = j; //save index } midpnt5 = (max5 + min5) / 2.0; //calculate midpoint voltage value (halfway between min and max) } //AN11: for(m=0;m max11){ //(all same logic as AN5) max11 = data11[m]; max11ind = m; } else if(data11[m] <= min11){ min11 = data11[m]; min11ind = m; } midpnt11 = (max11 + min11) / 2.0; } //mark min and max with red circles on the TFT plots tft_drawCircle(max5ind+80, 200-data5[max5ind]*60, 4, ILI9340_RED); tft_drawCircle(min5ind+80, 200-data5[min5ind]*60, 4, ILI9340_RED); tft_drawCircle(max11ind+80, 300-data11[max11ind]*60, 4, ILI9340_RED); tft_drawCircle(min11ind+80, 300-data11[min11ind]*60, 4, ILI9340_RED); //first determine if max or min comes first in time in data5 vector (i.e. if midpoint location is on falling or rising edge) //iterate through channel5 data to find midpoint index if(max5ind < min5ind){ //if the max index is LESS THAN the min index (ie max comes first in time, ie midpoint is on falling edge) for(k=0;k= midpnt5 && data5[k+2] <= midpnt5){ //find place in data where current data val > midpoint val and data val two indices from now < midpoint val midpnt5ind = k+1; //this means that the data point in between current and two indices from now IS the midpoint; save this index } } //want to compare midpoints of data5 and data11 on same place on waveform (in this case both on falling edge), so find this midpoint in data11 vector for(k=0;k= midpnt11 && data11[k+2] <= midpnt11){ //(same logic as for data5 above) midpnt11ind = k+1; } } } else if(max5ind > min5ind){ //if the max index is GREATER THAN the min index (ie min comes first in time, ie midpoint is on rising edge) for(k=0;k= midpnt5){ //find place in data where current data val < midpoint val and data val two indices from now > midpoint val midpnt5ind = k+1; //this means that the data point in between current and two indices from now IS the midpoint; save this index } } //want to compare midpoints of data5 and data11 on same place on waveform (in this case both on rising edge), so find this midpoint in data11 vector for(k=0;k= midpnt11){ //(same logic as for data5 above) midpnt11ind = k+1; } } } //check if midpoint location is correct (ie is between the max and min for both channels) //(only calculate blood pressure if midpoint location is correct; otherwise, throw out this data point) if(((midpnt5ind > min5ind && midpnt5ind < max5ind) || (midpnt5ind < min5ind && midpnt5ind > max5ind)) && ((midpnt11ind > min11ind && midpnt11ind < max11ind) || (midpnt11ind < min11ind && midpnt11ind > max11ind))){ lag_sec = abs((float)midpnt11ind - (float)midpnt5ind) / 66.67; //the lag between the two waveforms is the difference in time between their two midpoint locations (divide by sampling frequency to get seconds) //for calibration: to determine average lag, collect 50 data points from correct midpoint calculations lag_sec_vect[lag_ind] = lag_sec; //save it to array of lag times if(lag_ind == 49) { //once collected 50 lag times, take average and use this in calculation of BP sum = 0.0; for(z=0;z<50;z++){ sum = sum+lag_sec_vect[z]; } avg_lag_sec = sum / 50.0; //calculate BP BP = C*(arm_dist / avg_lag_sec); //Display blood pressure on TFT tft_fillRoundRect(0,25, 230, 15, 1, ILI9340_BLACK);// x,y,w,h,radius,color tft_setCursor(0, 25); tft_setTextColor(ILI9340_YELLOW); tft_setTextSize(1.5); sprintf(buffer, "Systolic Blood Pressure: \n%f", BP); tft_writeString(buffer); } lag_ind++; } //mark midpoints with green circles on the TFT plots tft_drawCircle(midpnt11ind+80, 300-data11[midpnt11ind]*60, 4, ILI9340_GREEN); tft_drawCircle(midpnt5ind+80, 200-data5[midpnt5ind]*60, 4, ILI9340_GREEN); //reset i to 0 to indicate need to recollect samples for AN5 and AN11 //reinitialize min and max values for next set of data points i = 0; max5 = 0.0; min5 = 3.3; max11 = 0.0; min11 = 3.3; PT_EXIT(pt); //exit protothread and go back to from where it was spawned PT_END(pt); } //============================================================================================================// /* ADC Thread Use ADC10 on the PIC32 to collect samples through AN5 and AN11, one for each sensor reading (arm and fingertip) When finished collecting samples, spawn BP calculation thread */ static PT_THREAD (protothread_adc(struct pt *pt)) { PT_BEGIN(pt); while(1) { // yield time 5 ms PT_YIELD_TIME_msec(5) ; if(i < num_samps){ //if haven't finished collecting samples yet //set ADC10 channel to channel 5 to sample from AN5 SetChanADC10(ADC_CH0_NEG_SAMPLEA_NVREF | ADC_CH0_POS_SAMPLEA_AN5); PT_YIELD_TIME_msec(5); //pause to allow PIC32 to switch channels channel5 = ReadADC10(0); //read the result of channel 5 conversion in the idle buffer //set ADC10 channel to channel 11 to sample from AN11 SetChanADC10(ADC_CH0_NEG_SAMPLEA_NVREF | ADC_CH0_POS_SAMPLEA_AN11); PT_YIELD_TIME_msec(5); //pause to allow PIC32 to switch channels channel11 = ReadADC10(0); //read the result of channel 11 conversion in the idle buffer //convert to voltage V5 = (float)channel5 * 3.3 / 1023.0 - 0.2; //offset of 0.2V determined by experimentation V11 = (float)channel11 * 3.3 / 1023.0 - 0.2; //save acquired voltage samples to data arrays data5[i] = V5; data11[i] = V11; i++; //increment i to iterate through data vectors } else if(i >= num_samps){ //have finished collecting samples, so plot new data set on TFT and spawn BP calculation thread //overwrite old plots before redrawing new data on TFT tft_fillScreen(ILI9340_BLACK); //create key in corner of TFT display (arm pulse, finger pulse, min and max, midpoint) tft_fillRoundRect(150,280, 230, 15, 1, ILI9340_BLACK);// x,y,w,h,radius,color tft_setCursor(150,280); tft_setTextColor(ILI9340_YELLOW); tft_setTextSize(1.5); sprintf(buffer, "-: Bicep Pulse"); tft_writeString(buffer); tft_setCursor(150,290); tft_setTextColor(ILI9340_CYAN); tft_setTextSize(1.5); sprintf(buffer, "-: Finger Pulse"); tft_writeString(buffer); tft_setCursor(150,300); tft_setTextColor(ILI9340_RED); tft_setTextSize(1.5); sprintf(buffer, "o: min/max"); tft_writeString(buffer); tft_setCursor(150,310); tft_setTextColor(ILI9340_GREEN); tft_setTextSize(1.5); sprintf(buffer, "o: midpoint"); tft_writeString(buffer); if(BP > 0.0){ //if a new BP value has been calculated, display it on the TFT tft_fillRoundRect(0,25, 230, 15, 1, ILI9340_BLACK);// x,y,w,h,radius,color tft_setCursor(0, 25); tft_setTextColor(ILI9340_YELLOW); tft_setTextSize(1.5); sprintf(buffer, "Systolic Blood Pressure: \n%f", BP); tft_writeString(buffer); } else { //otherwise, inform user that data is still being collected for calibration tft_fillRoundRect(80,25, 230, 15, 1, ILI9340_BLACK);// x,y,w,h,radius,color tft_setCursor(80, 25); tft_setTextColor(ILI9340_YELLOW); tft_setTextSize(1.5); sprintf(buffer, "Collecting data\n Please stand by"); tft_writeString(buffer); } //plot arm pulse and finger pulse on TFT for(n=0;n