const int LOAD_RESISTOR = 480; // Load resistor value in ohms
const int CURRENT_SENSE_RESISTOR = 100; // Current sense resistor value in ohms
const int MUX_CONTROL_PIN = 2; // Control pin for multiplexer
const int ANALOG_PIN = A1; // Analog pin for multiplexer output
const float REFERENCE_VOLTAGE = 5.0; // Reference voltage of the Arduino (5V)

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  pinMode(MUX_CONTROL_PIN, OUTPUT); // Set multiplexer control pin as output
}

void loop() {
  // Read voltage from the power supply (PSU)
  float psuVoltage;
  selectInput(0); // Select input channel 0 on the multiplexer
  psuVoltage = analogRead(ANALOG_PIN) * (REFERENCE_VOLTAGE / 1023.0); // Convert analog value to voltage
  
  // Read voltage across the load resistor
  float loadVoltage;
  selectInput(1); // Select input channel 1 on the multiplexer
  loadVoltage = analogRead(ANALOG_PIN) * (REFERENCE_VOLTAGE / 1023.0); // Convert analog value to voltage
  
  // Read voltage across the current sense resistor
  float currentSenseVoltage;
  selectInput(2); // Select input channel 2 on the multiplexer
  currentSenseVoltage = analogRead(ANALOG_PIN) * (REFERENCE_VOLTAGE / 1023.0); // Convert analog value to voltage
  
  // Calculate current flowing through the load resistor using Ohm's Law: I = V/R
  float loadCurrent = loadVoltage / LOAD_RESISTOR;
  
  // Calculate current flowing through the current sense resistor using Ohm's Law: I = V/R
  float currentSenseCurrent = currentSenseVoltage / CURRENT_SENSE_RESISTOR;
  
  // Calculate current divided between the load resistor and VCC: I = I_sense - I_load
  float dividedCurrent = currentSenseCurrent - loadCurrent;
  
  // Print measurements to Serial Monitor
  Serial.print("PSU Voltage: ");
  Serial.print(psuVoltage, 2); // Display PSU voltage with 2 decimal places
  Serial.print(" V, Load Voltage: ");
  Serial.print(loadVoltage, 2); // Display load voltage with 2 decimal places
  Serial.print(" V, Load Current: ");
  Serial.print(loadCurrent, 2); // Display load current with 2 decimal places
  Serial.print(" A, Divided Current: ");
  Serial.print(dividedCurrent, 2); // Display divided current with 2 decimal places
  Serial.println(" A"); // Add a newline character
  
  delay(1000); // Adjust delay as needed
}

void selectInput(int channel) {
  digitalWrite(MUX_CONTROL_PIN, LOW); // Disable multiplexer
  delayMicroseconds(5); // Wait for multiplexer to settle
  for (int i = 0; i < 3; i++) {
    digitalWrite(MUX_CONTROL_PIN, (channel >> i) & 1); // Set multiplexer control bits
  }
  digitalWrite(MUX_CONTROL_PIN, HIGH); // Enable multiplexer
}