ac arduino

#include <Arduino.h>

#define SQRT2 sqrt(2)
uint16_t adc_min, adc_max, adc_vpp, adc_now;
float adc_rms, adc_valx;

void setup() {
  delay(1000);
  Serial.begin(57600);

  adc_min = 1024;
  adc_max = 0;
}

void loop() {

  uint32_t tn = millis();
  adc_min = 1024;
  adc_max = 0;
  while (millis() - tn <= 50) {
    adc_now = analogRead(0);
    if (adc_now < adc_min) {
      adc_min = adc_now;
    }

    if (adc_now > adc_max) {
      adc_max = adc_now;
    }
  }
  // peak to peak value
  adc_vpp = (adc_max - adc_min);
  adc_rms = ((float)adc_vpp / 2.0) / SQRT2;
  adc_valx = adc_rms * 5 / 1024;

  // Serial.println(millis() + " : " + String(adc_valx*63*2, 3) + " -- " +
  //                String(adc_rms, 3) + " -- " + String(adc_vpp, DEC) + " -- "
  //                +
  //                String(adc_min, DEC) + " -- " + String(adc_max, DEC));
  Serial.println(millis() + " : " + String(adc_valx * 63 * 2, 3));
}