/*
  Code for triggering 5 millisecond pulses
  Source: Arduino Forum
  Topic: Triggering 5 millisecond pulses part #1
  Category: Using Arduino
  Subcategory: Programming Questions
  Link: https://forum.arduino.cc/t/triggering-5-millisecond-pulses-part-1/1135999/85
*/

// Define analog input pin
#define ainPin A0

// Define constants
#define compareVoltage 2.0f    // Voltage level used as a threshold for pulse triggering
#define pulseTime 50ul         // Duration of the pulse in milliseconds
#define hiAmplitude 6          // Amplitude value for the high state of the pulse
#define loAmplitude 1          // Amplitude value for the low state of the pulse

// Declare global variables
float input_voltage;          // Holds the current input voltage
uint32_t pulseStartAtMs;      // Records the start time of the pulse
bool inPulse;                 // Indicates whether the system is currently in a pulse state
uint8_t Millis;               // Stores the amplitude value for the pulse

// Setup function: runs once at the beginning
void setup() {
  // Start serial communication
  Serial.begin(115200);
 
  // Initialize variables
  input_voltage = 0.0f;   // Initializing input voltage variable
  inPulse = false;        // Setting inPulse variable to false initially
}

// Loop function: runs repeatedly
void loop() {
  // Read analog input
  int analog_value = analogRead(ainPin); // Read analog input from ainPin

  // Store previous input voltage
  float prevInputVoltage = input_voltage; // Store the previous input voltage

  // Calculate input voltage
  input_voltage = (analog_value * 5.0) / 1023.0f; // Convert analog value to input voltage

  // Check for the condition to start a pulse
  if (prevInputVoltage < compareVoltage && input_voltage >= compareVoltage) {
    Millis = hiAmplitude;     // Set pulse amplitude to high
    inPulse = true;
    pulseStartAtMs = millis(); // Record pulse start time
  }

  // Check if the pulse duration has elapsed
  if (inPulse && millis() - pulseStartAtMs >= pulseTime) {
    inPulse = false;          // End the pulse
    Millis = loAmplitude;     // Set pulse amplitude to low
  }

  // Print input voltage, pulse amplitude, and compare voltage
  Serial.println(
    "Input Voltage:= " + String(input_voltage, 2) + "V" 
    + ", Pulse Amplitude:= " + String(Millis) 
    + ", Compare Voltage:= " + String(compareVoltage, 2) + "V"
  );
}