#include <SPI.h>
#include <SD.h>
#include "Nextion.h"
#include "DFRobot_Heartrate.h"
#define heartratePin A0
#define LEVEL_LOW   (0)
#define CH0_OFFSET  (25)
char buffer[100] = {0};
static int ch0_data = LEVEL_LOW;


NexText txt_bpm  = NexText(0, 3, "t1");
NexWaveform s0 = NexWaveform(0, 1, "s0");
DFRobot_Heartrate heartrate(DIGITAL_MODE);

void setup() {
  Serial.begin(9600);
  if (!SD.begin(10)) {
    while (1);
  }
  nexInit();
}

void loop() {
  uint8_t rateValue;
  heartrate.getValue(heartratePin); 
  rateValue = heartrate.getRate();
  if (rateValue)  {
    File dataFile = SD.open("datalog.txt", FILE_WRITE);
    if (dataFile) {
      dataFile.print(String(rateValue) + ',');
      dataFile.close();
    }
    txt_bpm.setText(buffer); //bpm
    memset(buffer, 0, sizeof(buffer)); //bpm
    itoa(rateValue, buffer, 10); //bpm
  }
  unsigned long value = analogRead(A0);
  ch0_data = value / 4;
  s0.addValue(0, CH0_OFFSET + ch0_data);
}