c - 如何计算 ADC 读数的平均值？

Question

目的是将最新的 10 个 ADC 读数存储在一个数组中，然后计算它们的平均值以供其他地方使用。每次更新时删除最旧的。

关于 LED 时序，如果 ADC 读数在下面写的边界内，它必须将时序从 1s 切换到 0.25s，如何正确实现？我知道我的方法有效，但可以做得更好。至于 LED，如果按下开关，它们必须改变模式，如您所见，它们确实如此，但我再次确信它可以通过另一种更简单的方式完成!

以下是我的代码，我也确信有很多错误和足够的优化空间，我很乐意接受它!

#include <avr/io.h>
#define F_CPU 16000000UL
#include <util/delay.h>

#include <avr/io.h>
#include <avr/interrupt.h>
unsigned int timecount0;


unsigned int adc_reading;

volatile uint32_t timing = 1;
volatile uint32_t accumulator = 0;
volatile uint16_t average = 0;
volatile uint16_t samples = 0;


#define LED_RED PORTB = ((PORTB & ~0b00001110)|(0b00000010 & 0b00001110))
#define LED_GREEN PORTB = ((PORTB & ~0b00001110)|(0b00001000 & 0b00001110))
#define LED_BLUE PORTB = ((PORTB & ~0b00001110)|(0b00000100 & 0b00001110))
#define LED_RGB PORTB = ((PORTB & ~0b00001110)|(0b00001000 & 0b00001110))

#define DELAY_COUNT 6

volatile uint8_t portdhistory = 0xFF;


void Timer0_init(void)
{
    timecount0 = 0; // Initialize the overflow count. Note its scope
    TCCR0B = (5<<CS00); // Set T0 Source = Clock (16MHz)/1024 and put Timer in Normal mode

    TCCR0A = 0;         // Not strictly necessary as these are the reset states but it's good
    // practice to show what you're doing
    TCNT0 = 61;         // Recall: 256-61 = 195 & 195*64us = 12.48ms, approx 12.5ms
    TIMSK0 = (1<<TOIE0);    // Enable Timer 0 interrupt


    PCICR |= (1<<PCIE0);
    PCMSK0 |= (1<<PCINT0);
    sei();              // Global interrupt enable (I=1)

}


void ADC_init(void)
{
    ADMUX = ((1<<REFS0) | (0<<ADLAR) | (0<<MUX0));  /* AVCC selected for VREF,ADLAR set to 0, ADC0 as ADC input (A0)  */
    ADCSRA = ((1<<ADEN)|(1<<ADSC)|(1<<ADATE)|(1<<ADIE)|(7<<ADPS0));
                                        /* Enable ADC, Start Conversion, Auto Trigger enabled, 
                                           Interrupt enabled, Prescale = 32  */
    ADCSRB = (0<<ADTS0); /* Select AutoTrigger Source to Free Running Mode 
                            Strictly speaking - this is already 0, so we could omit the write to
                            ADCSRB, but included here so the intent is clear */
    sei(); //global interrupt enable
}


int main(void)
{
    ADC_init();
    Timer0_init();


    DDRD = 0b00100000;  /* set PORTD bit 5 to output  */
    DDRB = 0b00111110;  /* set PORTB bit 1,2,3,4,5 to output  */


    sei();              // Global interrupt enable (I=1)


    while(1)
    {
        if(!(PIND & (1<<PIND2)))
        {
            PORTD = PORTD |= (1<<PORTD5);
            PORTB = PORTB |= (1<<PORTB4);
            if(average>512)
            {
                PORTB = PORTB |= (1<<PORTB5);
            }

        }
        else
        {

            PORTD = PORTD &= ~(1<<PORTD5);
            PORTB = PORTB &= ~(1<<PORTB4);
        }




    }

}

ISR(TIMER0_OVF_vect)
{

        TCNT0 = 61;     //TCNT0 needs to be set to the start point each time
        ++timecount0;   // count the number of times the interrupt has been reached


        if(!(PIND & (1<<PIND3)))
        {           

        if (timecount0 >= 0)    // 40 * 12.5ms = 500ms
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00000000 & 0b00001110));
        }

        if (timecount0 >= 8*timing) 
        {
            LED_RED;
        }

        if (timecount0 >= 16*timing)    
        {
            LED_GREEN;
        }

        if (timecount0 >= 24*timing)    
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00000110 & 0b00001110));


        }
        if (timecount0 >= 32*timing)    
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00001000 & 0b00001110));


        }
        if (timecount0 >= 40*timing)    
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00001010 & 0b00001110));          

        }

        if (timecount0 >= 48*timing)    
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00001100 & 0b00001110));      



        }

        if (timecount0 >= 56*timing)    
        {
            PORTB = ((PORTB & ~0b00001110)|(0b00001110 & 0b00001110));  


        }

        if (timecount0 >= 64*timing)
        {

            timecount0 = 0;

        }

        }
        else
        {
            if (timecount0 >= 0)
            {

                PORTB = ((PORTB & ~0b00001110)|(0b00000000 & 0b00001110)); //ALL OFF
            }

            if (timecount0 >= 8*timing) 
            {
                LED_RED;
                //PORTB = ((PORTB & ~0b00001110)|(0b00000010 & 0b00001110)); //RED
            }

            if (timecount0 >= 16*timing)    
            {
                LED_GREEN;


            }

            if (timecount0 >= 24*timing)    
            {
                LED_BLUE;



            }
            if (timecount0 >= 32*timing)
            {

                timecount0 = 0;

            }
        }           

}

ISR (ADC_vect)  //handles ADC interrupts

{

    adc_reading = ADC;   //ADC is in Free Running Mode
    accumulator+= adc_reading;


    if ((adc_reading > 768) & (adc_reading <= 1024))
    {
        timing = 10;

    }

    if ((adc_reading >= 0) & (adc_reading<= 768) )
    {
        timing = 2.5;

    }


    samples++;

    if(samples == 10)
    {
        average = accumulator/10;
        accumulator = 0;
        samples = 0;
    }


}

Answer 1

根据您的处理器，您可以保持 ISR() 的速度并避免昂贵的 /,%。

LED 的东西，我会在定时器中断中处理。

#define N 10
volatile unsigned sample[N];
volatile unsigned count = 0;
volatile unsigned index = 0;
volatile unsigned sum = 0;

ISR (ADC_vect)  {
  if (count >= N) {
    sum -= sample[index];
  } else {
    count++;
  }
  sample[index] = ADC;
  sum += sample[index];
  index++;
  if (index >= N) {
    index = 0;
  }
}

unsigned ADC_GetAvg(void) {
  block_interrupts();
  unsigned s = sum;
  unsigned n = count;
  restore_interrupts();
  if (n == 0) {
    return 0; //ADC ISR never called
  }
  return (s + n/2)/n;  // return rounded average
}

---

我推荐 low pass filter 的整数版本。比上一个 N 的平均值。