// CD74HC4067 Multiplexer with Raspberry Pi Pico
// Arduino C++ Code

// Pin definitions
const int S0_PIN = 21;    // GP21 -> S0
const int S1_PIN = 20;    // GP20 -> S1  
const int S2_PIN = 19;    // GP19 -> S2
const int S3_PIN = 18;    // GP18 -> S3
const int EN_PIN = 22;    // GP22 -> EN (Enable)
const int COM_PIN = 26;   // GP26 -> COM (ADC0)

void setup() {
  // Initialize serial communication
  Serial.begin(115200);
  while (!Serial) {
    ; // Wait for serial port to connect
  }
  
  // Configure address pins as outputs
  pinMode(S0_PIN, OUTPUT);
  pinMode(S1_PIN, OUTPUT);
  pinMode(S2_PIN, OUTPUT);
  pinMode(S3_PIN, OUTPUT);
  
  // Configure enable pin as output
  pinMode(EN_PIN, OUTPUT);
  
  // Configure COM pin for analog reading
  pinMode(COM_PIN, INPUT);
  
  // Initialize to safe state
  disableMux();
  selectChannel(0);
  
  Serial.println("CD74HC4067 Multiplexer initialized");
  Serial.println("Channels 0-3 connected to potentiometers");
  delay(1000);
}

void loop() {
  Serial.println("\n--- Reading all channels ---");
  
  // Read from all 4 potentiometer channels
  for (int channel = 0; channel < 4; channel++) {
    float voltage = readChannel(channel);
    Serial.print("Channel ");
    Serial.print(channel);
    Serial.print(": ");
    Serial.print(voltage, 2);
    Serial.println("V");
    
    delay(100); // Small delay between readings
  }
  
  delay(2000); // Wait 2 seconds before next reading cycle
}

void enableMux() {
  digitalWrite(EN_PIN, LOW);  // Active LOW
  delayMicroseconds(100);     // Allow settling time
}

void disableMux() {
  digitalWrite(EN_PIN, HIGH); // Disabled
  delayMicroseconds(10);      // Brief delay
}

void selectChannel(int channel) {
  if (channel < 0 || channel > 15) {
    Serial.println("Error: Channel must be 0-15");
    return;
  }
  
  // Set address pins based on channel number (binary)
  digitalWrite(S0_PIN, (channel & 1) ? HIGH : LOW);        // Bit 0
  digitalWrite(S1_PIN, (channel & 2) ? HIGH : LOW);        // Bit 1
  digitalWrite(S2_PIN, (channel & 4) ? HIGH : LOW);        // Bit 2
  digitalWrite(S3_PIN, (channel & 8) ? HIGH : LOW);        // Bit 3
  
  delayMicroseconds(100); // Allow channel switching time
}

float readChannel(int channel) {
  // Safe reading sequence
  disableMux();           // Disable first
  selectChannel(channel); // Select desired channel
  enableMux();           // Enable multiplexer
  
  // Read analog value (12-bit ADC: 0-4095)
  int analogValue = analogRead(COM_PIN);
  
  // Convert to voltage (3.3V reference)
  float voltage = (analogValue * 3.3) / 1023;
  
  // Optional: disable after reading for power saving
  // disableMux();
  
  return voltage;
}

// Alternative function to read raw ADC value
int readChannelRaw(int channel) {
  disableMux();
  selectChannel(channel);
  enableMux();
  
  int rawValue = analogRead(COM_PIN);
  return rawValue;
}

// Function to test all 16 channels (if you have more sensors)
void testAllChannels() {
  Serial.println("\n--- Testing all 16 channels ---");
  
  for (int channel = 0; channel < 16; channel++) {
    float voltage = readChannel(channel);
    Serial.print("Ch");
    if (channel < 10) Serial.print("0"); // Pad single digits
    Serial.print(channel);
    Serial.print(": ");
    Serial.print(voltage, 3);
    Serial.print("V ");
    
    // New line every 4 channels for better formatting
    if ((channel + 1) % 4 == 0) Serial.println();
  }
  
  disableMux(); // Return to safe state
}