SpO2 algorithm used in MAX30101 onboard MAX32620HSP. Algorithm is not perfect but it works
Dependencies: mbed MAX14720 USBDevice
Diff: main.cpp
- Revision:
- 0:af4d13000e95
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/main.cpp Thu Mar 28 08:07:54 2019 +0000 @@ -0,0 +1,144 @@ +#include "mbed.h" +#include "MAX14720.h" +#include "MAX30102.h" +#include "USBSerial.h" +#include "System.h" +#include "algorithm.h" + +/// define the HVOUT Boost Voltage default for the MAX14720 PMIC +#define HVOUT_VOLTAGE 4500 // set to 4500 mV + +#define MAX14720_I2C_SLAVE_ADDR (0x54) + +#define MAX_BRIGHTNESS 255 + +uint32_t aun_ir_buffer[500]; //IR LED sensor data +int32_t n_ir_buffer_length; //data length +uint32_t aun_red_buffer[500]; //Red LED sensor data +int32_t n_sp02; //SPO2 value +int8_t ch_spo2_valid; //indicator to show if the SP02 calculation is valid +int32_t n_heart_rate; //heart rate value +int8_t ch_hr_valid; //indicator to show if the heart rate calculation is valid +uint8_t uch_dummy; + +//Serial pc(USBTX, USBRX); //initializes the serial port +/// Define with Maxim VID and a Maxim assigned PID, set to version 0x0001 and non-blocking + +USBSerial usbSerial(0x0b6a, 0x0122, 0x0001, false); + +/// I2C Master 2 +I2C i2c2(I2C2_SDA, I2C2_SCL); // used by MAX14720, MAX30101, LIS2DH +/// SPI Master 0 with SPI0_SS for use with MAX30001 + +MAX14720 max14720(&i2c2, MAX14720_I2C_SLAVE_ADDR); +DigitalOut led(LED1); +DigitalIn INT(P4_0); +int main(){ +//--------------------------------------------------- + // hold results for returning functions + int result; + // initialize HVOUT on the MAX14720 PMIC + result = max14720.init(); + if (result == MAX14720_ERROR){ + printf("Error initializing MAX14720"); + } + max14720.boostEn = MAX14720::BOOST_ENABLED; + max14720.boostSetVoltage(HVOUT_VOLTAGE); +//--------------------------------------------------- + uint32_t un_min, un_max, un_prev_data; //variables to calculate the on-board LED brightness that reflects the heartbeats + int i; + int32_t n_brightness; + float f_temp; + long unBlockedValue = 0; + + maxim_max30102_reset(); //resets the MAX30102 + wait(1); + maxim_max30102_init(); //initializes the MAX30102 + + n_brightness=0; + un_min=0x3FFFF; + un_max=0; + + n_ir_buffer_length=500; //buffer length of 100 stores 5 seconds of samples running at 100sps + + //read the first 500 samples, and determine the signal range + for(i=0;i<n_ir_buffer_length;i++) + { + while(INT.read()==1); //wait until the interrupt pin asserts + + maxim_max30102_read_fifo((aun_red_buffer+i), (aun_ir_buffer+i)); //read from MAX30102 FIFO + + if(un_min>aun_red_buffer[i]) + un_min=aun_red_buffer[i]; //update signal min + if(un_max<aun_red_buffer[i]) + un_max=aun_red_buffer[i]; //update signal max + /*usbSerial.printf("red="); + usbSerial.printf("%i", aun_red_buffer[i]); + usbSerial.printf(", ir="); + usbSerial.printf("%i\n\r", aun_ir_buffer[i]);*/ + } + un_prev_data=aun_red_buffer[i]; + + + //calculate heart rate and SpO2 after first 500 samples (first 5 seconds of samples) + maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_sp02, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid); + + //Continuously taking samples from MAX30102. Heart rate and SpO2 are calculated every 1 second + + + while (1) { + i=0; + un_min=0x3FFFF; + un_max=0; + + //dumping the first 100 sets of samples in the memory and shift the last 400 sets of samples to the top + for(i=200;i<500;i++) + { + aun_red_buffer[i-200]=aun_red_buffer[i]; + aun_ir_buffer[i-200]=aun_ir_buffer[i]; + + //update the signal min and max + if(un_min>aun_red_buffer[i]) + un_min=aun_red_buffer[i]; + if(un_max<aun_red_buffer[i]) + un_max=aun_red_buffer[i]; + } + + //take 100 sets of samples before calculating the heart rate. + for(i=300;i<500;i++) + { + un_prev_data=aun_red_buffer[i-1]; + while(INT.read()==1); + maxim_max30102_read_fifo((aun_red_buffer+i), (aun_ir_buffer+i)); + + if(aun_red_buffer[i]>un_prev_data) + { + f_temp=aun_red_buffer[i]-un_prev_data; + f_temp/=(un_max-un_min); + f_temp*=MAX_BRIGHTNESS; + n_brightness-=(int)f_temp; + if(n_brightness<0) + n_brightness=0; + } + else + { + f_temp=un_prev_data-aun_red_buffer[i]; + f_temp/=(un_max-un_min); + f_temp*=MAX_BRIGHTNESS; + n_brightness+=(int)f_temp; + if(n_brightness>MAX_BRIGHTNESS) + n_brightness=MAX_BRIGHTNESS; + } + //send samples and calculation result to terminal program through UART + /*usbSerial.printf("red="); + usbSerial.printf("%i", aun_red_buffer[i]); + usbSerial.printf(", ir="); + usbSerial.printf("%i", aun_ir_buffer[i]);*/ + usbSerial.printf("HR=%i\t", n_heart_rate); + //usbSerial.printf("HRvalid=%i, ", ch_hr_valid); + usbSerial.printf("SpO2=%i\n\r", n_sp02); + //usbSerial.printf("SPO2Valid=%i\n\r", ch_spo2_valid); + } + maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_sp02, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid); + } +} \ No newline at end of file