ACS712 Current Sensor (20A) with a Raspberry Pi Pico

// ACS712 Current Sensor (20A) on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/acs712-current-sensor/raspberry-pi-pico
#include <Arduino.h>

// ACS712 on a Raspberry Pi Pico: OUT reaches GP28 through a 10 kΩ / 20 kΩ divider,
// so the pin sees 2/3 of OUT (the 2.5 V zero becomes about 1.67 V).
const int SENSE_PIN = 28;           // GP28 (ADC2)
const float SENS_V_PER_A = 0.100;   // 20 A module (0.185 for 5 A, 0.066 for 30 A)
const float ADC_VREF = 3.3;         // the Pico's ADC reference: its 3.3 V rail
const float ADC_STEPS = 4096.0;     // 12 bits, set in setup() (arduino-pico defaults to 10)
const float DIVIDER = 1.5;          // (10 kΩ + 20 kΩ) / 20 kΩ: OUT = pin voltage x 1.5
const int SAMPLES = 64;
float zeroV = 2.5;                  // OUT with no current (VCC / 2), measured in setup()

float readOutVolts() {
  uint32_t sum = 0;
  for (int i = 0; i < SAMPLES; i++) sum += analogRead(SENSE_PIN);
  return (sum / (float)SAMPLES) * ADC_VREF / ADC_STEPS * DIVIDER;
}

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  delay(100);
  zeroV = readOutVolts();           // start with no current flowing
  Serial.print("ACS712 ready, zero at ");
  Serial.print(zeroV, 3);
  Serial.println(" V");
}

void loop() {
  float amps = (readOutVolts() - zeroV) / SENS_V_PER_A;
  Serial.print("Current: ");
  Serial.print(amps, 3);
  Serial.print(" A  (");
  Serial.print(amps * 1000.0, 0);
  Serial.println(" mA)");
  delay(500);
}