Log Battery voltage vs. time

battery.c

#include <Arduino.h>
#include <ArduinoNvs.h>
const bool LOG = true;
uint16_t minutesSinceBoot = 0;
bool doLogging = false;
void setup()
{
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(2, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(35, INPUT);
  pinMode(34, INPUT);
  digitalWrite(2, LOW);
  digitalWrite(4, LOW);
  NVS.begin();
  uint16_t currentDuration = NVS.getInt("LOG");
  Serial.printf("Minutes since boot: %d \n", currentDuration);
  doLogging = currentDuration < 10 && LOG;
  Serial.println(doLogging  ? "LOGGING" : "CHARGING");
  for(int i=0; i<currentDuration; i++) {
    Serial.print(currentDuration - i);
    Serial.print(' ');
    Serial.println(NVS.getFloat("NFL-" + (i+1)));
  }
}

void loop()
{
  float v = (float)(analogRead(34)) / 4095 * 2 * 3.3 * 1.1;
  if (!doLogging)
  {
    Serial.println(v);
    delay(1000);
  }
  else
  {
    delay(60000);
    NVS.setInt("LOG", ++minutesSinceBoot);
    NVS.setFloat("NFL-" + minutesSinceBoot, v);
  }
}