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我試圖實現Binary Code Modulation（也稱爲位角度調製，BAM），作爲PWM的替代方案，因爲PWM引腳數量最少Arduino的。使用BAM的想法是，LED將在不連續的時間開啓和關閉，從而有效地控制LED的亮度。這個「時間」由字節中相應的位值決定。Arduino（AVR ATMega328）Timer1似乎沒有在正確的時間觸發
例如，如果設置爲值85（在255），這是在二進制01010101，這意味着LED將交替接通和斷開狀態，但對於不同的時間長度。第0位'1'表示LED將點亮1滴，而第6位'0'表示LED將熄滅32滴，等等。目標是，這將使LED快速切換到人眼不會注意的位置，從而根據數值產生亮度錯覺。較高的值將涉及較亮的LED顏色。
在實施這一點，我注意到，在LED的刷新速率可以看出。我可以看到LED何時開啓以及何時關閉。它似乎每半秒鐘切換一次港口。因爲我沒有示波器，所以不用等待。我在Arduino上使用Timer1來每8微秒（125KHz）中斷一次。每個中斷將更新連接到LED的PIN的狀態，如果它打開或關閉。
我試着這樣做既使用Timer1 library，並通過寄存器去，但似乎都產生錯誤的結果。目前，我的代碼正在切換一個引腳。如果中斷是工作正常（每8us更新一次），那麼我應該看到藍色LED（連接到引腳8）切換狀態每個滴答聲。我的眼睛應該看到的只是一個LED。
注：當定時器1 lib和寄存器之間的切換，只是名字我ISR變化。請參閱代碼中的評論。
可有人請看看我的定時器實現。我有一種感覺，這是問題可能出現的地方，但我無法弄清楚。
#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;
}