It looks like you're working on an AVR project where you're trying to convert an analog signal to a digital value using the ADC, and then use that digital value to control the duty cycle of a PWM signal. Your goal is to have the ADC conversion automatically start the next conversion in Free-Running mode, but it's not working as expected.
In Free-Running mode, the ADC should automatically start the next conversion after the previous one finishes, without needing to manually set the `ADSC` bit. Based on your code, there are a few areas to consider to ensure Free-Running mode works correctly:
1. **Configuration of ADCSRA**:
Ensure that `ADATE` (ADC Auto Trigger Enable) is set properly. Since you are using Free-Running mode, you need to have `ADATE` set, which you do correctly.
2. **Auto-Trigger Source**:
For Free-Running mode, ensure that the `ADCSRB` register is set correctly to select Free-Running mode. You have set `ADCSRB` to 0, which should be fine, but it's good to double-check.
3. **Starting the First Conversion**:
You are starting the first conversion correctly with `ADCSRA |= (1 << ADSC);`, so this is good.
4. **Interrupt Handling**:
In the `ISR(ADC_vect)`, you don't need to manually start a new conversion if you're in Free-Running mode, because it should already be doing that. Removing the `ADCSRA |= (1 << ADSC);` line from the ISR might solve your issue.
Here's an adjusted version of your code that should work correctly for Free-Running mode:
```c
void timerSetup() {
// Configure Timer1 for Fast PWM mode, non-inverted, 8-bit resolution
TCCR1A = (1 << WGM10) |(1<<COM1A0)|(1 << COM1A1)|(1<<WGM11); // Fast PWM 10 BIT, non-inverted mode
TCCR1B = (1 << WGM12) | (1 << CS11) |(1<<CS10); // Prescaler = 64
ICR1 = 1023; // FREQUENCY 250HZ
OCR1A= 300; // INITIAL dutyCycle
}
void setup() {
// Set PORTB pin 1 (OC1A) as output for PWM
DDRB |= (1 << PB1);
// Initialize Serial communication
Serial.begin(9600);
// Setup the timer
timerSetup();
// Configure ADC
ADMUX = 0x00; // Use ADC0, Vref = AVcc
ADCSRB = 0x00; // Free-running mode
ADCSRA = (1 << ADEN) | (1 << ADATE) | (1 << ADPS2) | (1 << ADPS1); // Set ADC prescaler and enable ADC
// Start the first ADC conversion
ADCSRA |= (1 << ADSC);
}
void loop() {
// Main loop remains empty; all work is done in interrupts
}
ISR(ADC_vect) {
// Read the ADC value and update the PWM duty cycle
OCR1A = ADC; // dutycycle value equals provided by ADC
Serial.println(ADC);
// No need to manually start a new conversion here
}
```
### Key Points:
- Ensure `ADATE` is set to enable Auto Trigger.
- `ADCSRB` should be set to 0 for Free-Running mode (which it is in your case).
- The `ADCSRA |= (1 << ADSC);` in the ISR is redundant for Free-Running mode and can be removed.
This configuration ensures that the ADC keeps converting automatically and triggers the interrupt routine each time a conversion completes.
