Question

由于Arduino上的PWM引脚数量最少，我试图实现Binary Code Modulation（也称为比特角调制，BAM）作为PWM的替代方案。使用BAM背后的想法是LED将在不连续的时间内打开和关闭，有效地控制LED的亮度。该“时间”由字节中的相应位值确定。

例如，如果设置为值85（满分为255），即二进制的01010101，则表示LED将交替打开和关闭状态，但是对于不同的时间长度。第0位“1”表示LED将打开1个刻度，而第6位“0”表示LED将关闭32个刻度，依此类推。我们的目标是将LED足够快地切换到人眼不会注意到的地方，根据价值创造出亮度的幻觉。较高的值与较亮的LED颜色有关。

在实现这一点时，我注意到可以看到LED上的刷新率。我可以看到LED何时开启以及何时关闭。它似乎每半秒切换一次端口。由于我没有示波器，因此无需等待。我在Arduino上使用Timer1来中断每8微秒（125KHz）。如果打开或关闭，每个中断都将更新连接到LED的PIN的状态。

我尝试使用Timer1 library并通过寄存器来执行此操作，但两者似乎都会产生错误的结果。目前，我的代码是切换一个引脚。如果中断正常工作（每8us更新一次），那么我应该看到蓝色LED（连接到引脚8）切换状态。我的眼睛应该看到的只是一个LED。

注意：当在Timer1 lib和寄存器之间切换时，我的ISR会在名称中发生变化。请参阅代码中的注释。

请有人看看我的Timer实现。我觉得这可能是问题所在，但我无法弄明白。

    #include <TimerOne.h>
    #include <SPI.h>
    #include "avr/io.h"
    #include "LEDArray.h"

    #define TIMER_US        (8) //125KHz in microseconds
    #define NUM_OF_LEDS     ((LEDS_PER_ROW)*(LEDS_PER_COL))
    #define LEDS_PER_ROW    (8)
    #define LEDS_PER_COL    (8)

    volatile byte BAM_pos = 0;
    volatile byte BAM_tick = 0;

    // OutputDataH, OutputDataM, and OutputDataL
    // totals to 24 bits. There are 24 pins
    // that I need to shift data to. These three variables
    // will hold the data value corresponding to the associated 
    // bit level
    volatile byte OutputDataH = 0;
    volatile byte OutputDataM = 0;
    volatile byte OutputDataL = 0;
    //bool UpdateLedOutput = 1;

    volatile byte green = 0;
    volatile byte blue = 0;

    void InitTimer(){
      TCCR1A = 0;
      TCCR1B = 0;
      TCNT1  = 0;

      OCR1A = 127;            // compare match register == 16MHz/((prescalar=1)*125KHz) - 1
      TCCR1B |= (1 << WGM21);   // CTC mode
      TCCR1B |= (1<<CS20);    // 1x prescaler 
      TIMSK1 |= (1 << OCIE1A);  // enable timer compare interrupt
    }

    void InitPins(){
        // initialize the digital pin as an output.
        SHIFT_REGISTER |= (DATA | CLOCK | SS );
        // set control pins as low
        SHIFT_PORT &= ~(DATA | LATCH | CLOCK);

            // initialize the led pins for testing
            pinMode(4, OUTPUT);
            pinMode(8, OUTPUT);
    }

    ISR(TIMER0_COMPA_vect){
    //void timerISR(){ //use this with Timer1 Library instead
        //ISR(TIMER1_COMPA_vect){
        //Move onto next bit, reset BAM state
        if(BAM_tick >= 120){ //8 + 16 + 32 + 64
            BAM_tick = 0;
            BAM_pos = 0;
        }

        // Move onto the next bit at these ticks. Ticks are in 8 microsecond increments
        if(BAM_tick==8 || BAM_tick == 24 || BAM_tick == 56){
            BAM_pos++;
        }

        BAM_pos %= 4; //wrap counter after going through four bits

    // if(UpdateLedOutput){ Change the LED state only when the bit position is updated

            //For every LED, look at enabled bit, if true determine corresponding LEDs_Output bits through the LEDs rgb values
            //There are 3 groups of LEDs, each using 1 byte (8 bits -> 8 pins)
            //We, therefore, have a HIGH, MIDDLE, and LOW byte values that we will shift out
            for(int i=0; i<8; i++){
                if( ((ledOutput.all) & (1<<i))){ 
                //ledOutput.all is of size 24 bits. each bit tells us whether the pin should be enabled for this tick or not
                    OutputDataH |= (1<<i);
                }
            }
            for(int i=8; i<16; i++){
                if( ((ledOutput.all) & (1<<i))){
                    OutputDataM |= (1<<i);
                }
            }
            for(int i=16; i<24; i++){
                if( ((ledOutput.all) & (1<<i))){
                    OutputDataL |= (1<<i);
                }
            }           

            UpdateLedOutput = 0;
    //  }

        //Update LED OUTPUT after we have reach the end of the bits time
    //  if(BAM_tick==8 || BAM_tick == 24 || BAM_tick == 56){
    //      UpdateLedOutput = 1;
    //  }

        //Consume the tick
        BAM_tick++;

        //Shift out the data
        /*Latch_Low();
        sendData(OutputDataH);
        sendData(OutputDataM);
        sendData(OutputDataL);
        Latch_High();
        Latch_Low();
        */


        //different shifting data
    /*
        if(green & (1<<BAM_pos))
            //PORTD |= (1<<PORTD4);
            digitalWrite(4, LOW);
        else 
            digitalWrite(4, HIGH);
           //PORTD &= (0<<PORTD4);

        if(blue & (1<<BAM_pos))
            //PORTB |= (1<<PORTB0);
            digitalWrite(8, LOW);
        else 
            digitalWrite(8, HIGH);//PORTB &= (0<<PORTB0);
        */
        digitalWrite(8, digitalRead(8) ^1);
    }




    void setup() {
         InitData();
         InitPins();
         InitTimer();
        //Timer1.initialize(TIMER_US); 
        //Timer1.attachInterrupt(timerISR);
         EnableSPI(); //Enable SPI as Master
         Serial.begin(9600);
    }


    void loop() {
        // do almost nothing!
       while(1){
         PulseThroughColors();
       }
    }

    //This should slowly increase the brightness of the corresponding pin on the RGB LED
    // Blue should increase brightness, and then decrease it in the opposite manner, indefinitely
    void PulseThroughColors(){
        blue = 0;
        green = 0;
        int i=0;
        for(i=0; i< 255; i++)
            blue = i;
        for (i=255; i>0; i--)
            blue = 0;
        //for(i=0; i< 255; i++)
        //  green = i;
        //for (i=255; i>0; i--)
        //  green  = 0;
    }

Answer 1

所以我的代码中有两个错误。首先，我将计数器加速到250KHz（4us）中断。其次，我设置BAM级别（接近ISR结束）的方式不正确。我忘了我有一个共阳极LED，这意味着为了打开一个颜色，我必须将相应的引脚设置为LOW，而不是HIGH，如我的例子中所示。固定段位于下方。谢谢所有看过这个的人。

void InitTimer(){
    TCCR1A = 0;
    TCCR1B = 0;
    TCNT1  = 0;

    TCCR1A = B00000000;
    TCCR1B = B00001011;
    OCR1A=30;
    TIMSK1 = B00000010;
}

ISR(...){
 ........
if(green & (1<<BAM_pos))
    PORTD &= ~(1<<PORTD4);
else 
   PORTD |= (1<<PORTD4);

if(blue & (1<<BAM_pos))
    PORTB &= ~(1<<PORTB0);
else 
    PORTB |= (1<<PORTB0);
}

Arduino（AVR ATMega328）Timer1似乎没有在合适的时间触发

1 个答案: