// Define TC0 Channel 0 registers and parameters
#include "variant.h"

// Pin 9 is PB25, which maps to TIOA0 (Peripheral B)
const uint32_t PIN_MASK = PIO_PB25;

void setup() {
  // Initialize Serial communication at 115200 baud
  Serial.begin(115200);
  while (!Serial);

  // 1. Enable peripheral clock for TC0 (Channel 0 is ID 27)
  PMC->PMC_PCER0 = (1 << ID_TC0);

  // 2. Configure Pin 9 (PB25) for Peripheral B (TIOA0)
  PIOB->PIO_ABSR |= PIN_MASK;   // Set to Peripheral B
  PIOB->PIO_PDR |= PIN_MASK;    // Disable PIO, enable peripheral control

  // 3. Configure TC0 Channel 0 in Waveform Mode
  // Waveform mode, clock MCK/2, toggle TIOA on RC compare match
  TC0->TC_CHANNEL[0].TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK1 | // MCK/2 clock source
                              TC_CMR_WAVE |                 // Waveform mode
                              TC_CMR_WAVSEL_UP_RC |         // UP mode with automatic trigger on RC compare
                              TC_CMR_ACPA_CLEAR |           // Clear TIOA on RA compare
                              TC_CMR_ACPC_SET;              // Set TIOA on RC compare

  // 4. Set initial frequency (e.g., 1 kHz based on 84MHz / 2 = 42MHz master clock)
  // Frequency = (MCK / 2) / RC -> For 1 kHz: 42,000,000 / 1000 = 42000
  setTimerFrequency(1000);

  // Enable and start the counter
  TC0->TC_CHANNEL[0].TC_CCR = TC_TC_CLKEN | TC_TC_SWTRG;

  Serial.println("Arduino Due TC0 Waveform Generator Initialized.");
  Serial.println("Send a frequency value (in Hz) via Serial to update the rate.");
}

void loop() {
  // Check if data is available on the serial port to change the rate/bits
  if (Serial.available() > 0) {
    long inputVal = Serial.parseInt();
    
    if (inputVal > 0) {
      if (inputVal < 100) {
        // Example logic: if a small number is sent, treat it as a bit pattern command or scale
        Serial.print("Received pattern/command scale: ");
        Serial.println(inputVal);
      } else {
        // Treat as frequency in Hz
        setTimerFrequency(inputVal);
        Serial.print("Updated frequency to: ");
        Serial.print(inputVal);
        Serial.println(" Hz");
      }
    }
  }
}

void setTimerFrequency(uint32_t frequencyHz) {
  // Prevent division by zero or out-of-range values
  if (frequencyHz == 0) frequencyHz = 1;
  
  // The Due's peripheral clock (MCK) is 84 MHz. 
  // TIMER_CLOCK1 uses MCK/2 = 42 MHz.
  uint32_t rad = 42000000 / frequencyHz;
  
  if (rad > 65535) rad = 65535; // RC is a 16-bit register
  if (rad < 2) rad = 2;

  // Set RA to 50% duty cycle, RC to the full period count
  TC0->TC_CHANNEL[0].TC_RA = rad / 2;
  TC0->TC_CHANNEL[0].TC_RC = rad;
  
  // Software trigger to reload values immediately
  TC0->TC_CHANNEL[0].TC_CCR = TC_TC_SWTRG;
}