Arduino (AVR ATMega328) Timer1 似乎没有在正确的时间触发

Question

I am trying to implement Binary Code Modulation (also known as Bit Angle Modulation, BAM), as an alternative to PWM due to the minimal number of PWM pins on the Arduino. The idea behind using BAM is that the LED will be on and off in discrete times, effectively controlling the brightness of the LED. This "time" is determined by corresponding bit value in the byte.

For example, if set to the value 85 (out of 255), which is 01010101 in binary, this means that the LED will alternate on and off states, but for different time lengths. The 0th bit '1' means the LED will be on for 1 tick, while the 6th bit '0' means the LED will be off for 32 ticks, and so forth. The goal is that this will toggle the LED fast enough to where the human eye won't notice, creating the illusion of brightness depending on the value. A higher value would relate to a brighter LED color.

While implementing this, I noticed that the refresh rate on the LED could be seen. I can see when the LED is on and when it is off. It appears to toggle the port once every half second. There's no wait to know since I do not have an oscilloscope. I am using Timer1 on the Arduino to interrupt every 8 microseconds (125KHz). Each interrupt will update the status on the PIN connected to the LED, if it is on or off.

I've tried doing this using both the Timer1 library , and going through the registers, but both seem to produce erroneous results. Currently, my code is toggling one pin. If the interrupt is working properly (updating every 8us), then I should see the blue LED (connected to pin 8) toggle states every tick. What my eye should see is just an LED on.

Note: When switching between Timer1 lib and the registers, my ISR changes just in name. See the comment in code.

Can someone please look at my Timer implementation. I have a feeling this is where the problem might lie, but I cannot figure it out.

    #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

So there were two bugs in my code. First, I upped the counter to interrupt at 250KHz (4us). Secondly, the way I was setting my BAM levels (near the end of the ISR) was incorrect. I forgot that I have a common anode LED, which means that in order to turn on a color, I have to set the corresponding pin LOW, not HIGH as shown in my example. The fixed segments are located below. Thank you all who looked at this.

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);
}