#include <SPI.h>

#define CS 5

void setup() {
  Serial.begin(115200);
  SPI.begin(18, 19, 23, CS);
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
}

uint16_t readADC(uint8_t channel) {
  digitalWrite(CS, LOW);

  SPI.transfer(1);
  uint8_t highByte = SPI.transfer((8 + channel) << 4);
  uint8_t lowByte = SPI.transfer(0);

  digitalWrite(CS, HIGH);

  return ((highByte & 3) << 8) | lowByte;
}

void loop() {
  uint16_t value = readADC(0);
  Serial.print("ADC Value: ");
  Serial.println(value);
  delay(1000);
}