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我对 Arduino 编程很陌生。然而，我已经编码了一段时间。我目前正在尝试使用 Arduino IDE 和 Digispark Attiny85 开发板编写复调钢琴。要一次播放多个音符，我使用的是正弦表和快速 PWM。这是我的代码：

int val = 1;
uint8_t C = 0;
uint8_t D = 0;
uint8_t E = 0;
uint8_t F = 0;
uint8_t G = 0;
uint8_t A = 0;
uint8_t B = 0;

static uint8_t  sin_C[123] = {16,16,17,18,19,20,20,21,22,23,23,24,25,25,26,27,27,28,28,29,29,30,30,30,31,31,31,31,31,31,31,31,31,31,31,31,31,31,30,30,30,29,29,28,28,27,27,26,25,25,24,23,23,22,21,20,20,19,18,17,16,16,15,14,13,12,11,11,10,9,8,8,7,6,6,5,4,4,3,3,2,2,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,2,2,3,3,4,4,5,6,6,7,8,8,9,10,11,11,12,13,14,15,15};
static uint8_t sin_D[110] = {16,16,17,18,19,20,21,22,23,23,24,25,26,26,27,28,28,29,29,30,30,30,31,31,31,31,31,31,31,31,31,31,31,31,30,30,30,29,29,28,27,27,26,25,25,24,23,22,21,20,20,19,18,17,16,15,14,13,12,11,11,10,9,8,7,6,6,5,4,4,3,2,2,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,2,2,3,3,4,5,5,6,7,8,8,9,10,11,12,13,14,15,15};
static uint8_t sin_E[98] = {16,17,18,19,20,21,22,23,23,24,25,26,27,27,28,29,29,30,30,31,31,31,31,31,31,31,31,31,31,31,30,30,30,29,28,28,27,26,26,25,24,23,22,21,20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,5,4,3,3,2,1,1,1,0,0,0,0,0,0,0,0,0,0,0,1,1,2,2,3,4,4,5,6,7,8,8,9,10,11,12,13,14,15};
static uint8_t sin_F[92] = {16,17,18,19,20,21,22,23,24,25,26,27,27,28,29,29,30,30,31,31,31,31,31,31,31,31,31,31,30,30,30,29,28,28,27,26,25,24,23,22,21,20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,3,2,1,1,1,0,0,0,0,0,0,0,0,0,0,1,1,2,2,3,4,4,5,6,7,8,9,10,11,12,13,14,15};
static uint8_t sin_G[82] = {16,17,18,19,20,22,23,24,25,26,27,28,28,29,30,30,31,31,31,31,31,31,31,31,31,30,30,29,29,28,27,26,25,24,23,22,21,20,19,17,16,15,14,12,11,10,9,8,7,6,5,4,3,2,2,1,1,0,0,0,0,0,0,0,0,0,1,1,2,3,3,4,5,6,7,8,9,11,12,13,14,15};
static uint8_t sin_A[73] = {16,17,18,20,21,22,24,25,26,27,28,29,29,30,31,31,31,31,32,31,31,31,31,30,29,29,28,27,26,25,24,22,21,20,18,17,16,14,13,11,10,9,7,6,5,4,3,2,2,1,0,0,0,0,0,0,0,0,0,1,2,2,3,4,5,6,7,9,10,11,13,14,15};
static uint8_t sin_B[65] = {16,17,19,20,22,23,24,26,27,28,29,30,30,31,31,31,32,31,31,31,30,30,29,28,27,26,24,23,22,20,19,17,16,14,12,11,9,8,7,5,4,3,2,1,1,0,0,0,0,0,0,0,1,1,2,3,4,5,7,8,9,11,12,14,15};

ISR(TIMER0_COMPA_vect) {
  C++;
  D++;
  E++;
  F++;
  G++;
  A++;
  B++;
  if(C>122) {
    C = 0;
  }
  if(D>109) {
    D = 0;
  }
  if(E>97) {
    E = 0;
  }
  if(F>91) {
    F = 0;
  }
  if(G>81) {
    G = 0;
  }
  if(A>72) {
    A = 0;
  }
  if(B>64) {
    B = 0;
  }
  int values[7] = {sin_C[C],sin_D[D],sin_E[E],sin_F[F],sin_G[G],sin_A[A],sin_B[B]};
  OCR0A = values[val];
}

void setup() {
  DDRB |= (1<<PB0);
  TCNT0 = 0;
  TCCR0A=0;
  TCCR0B=0;
  TCCR0A |=(1<<COM0A1);
  TCCR0A |=(1<<WGM01);
  TCCR0A |=(1<<WGM00);
  TCCR0B |= (1 << CS00);
  OCR0A=254;
  TIMSK |= (1<<OCIE0A);
}

void loop() {
}

目前我无法使用变量来控制我应该播放的音符，即即使它编译，这条线也不起作用：

OCR0A = values[val];

其中 val 是我设置的全局变量。

我想知道是否有某种方法可以做到这一点或达到与我替换线相同的效果

OCR0A = values[1] + values[3] + values[5];

对于前面提到的，Attiny85 输出一个 D 和弦，就像它应该的那样。但是，我希望注释由按钮控制，因此我需要能够在程序运行时更改它们，而全局变量是我能想到的唯一方法。任何解决方案将不胜感激。

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1 回答 1

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使用全局变量是在主程序循环和中断处理程序之间进行数据通信的唯一方法。

在撰写此回复时，我发现您应该真正考虑在正弦表中使用有符号值。数学需要签名加法才能正常工作。

这一行：

OCR0A = values[val];

只能产生单声道声音。

您走在正确的道路上：

int values[7] = {sin_C[C],sin_D[D],sin_E[E],sin_F[F],sin_G[G],sin_A[A],sin_B[B]};

尽管。

所以，是的，另一个全局变量应该可以解决问题：

unsigned char notes_played;  // bits 0-7 map C-D notes

在您的 ISR 中：

ISR(TIMER0_COMPA_vect)
{
    //...

    int values[7] = {sin_C[C],sin_D[D],sin_E[E],sin_F[F],sin_G[G],sin_A[A],sin_B[B]};

    int ocr_value = 0;
    for (unsigned char mask = 1, i = 0; mask < 0x80; mask <<= 1, ++i)
    {
        if (mask & note_played)
           ocr_value += (signed char)(values[i] - 16);  // hints that using signed values 
                                                        // in sine tables may be more 
                                                        // efficient.
    }

    // need to 'clip' OCR here?
    if (ocr_value < -(OCR_RANGE / 2))
        ocr_value = -(OCR_RANGE / 2);
    if (ocr_value > (OCR_RANGE / 2))
        ocr_value = (OCR_RANGE / 2);

    OCRA0 = (unsigned char)((ocr_value + OCR_ZERO) & 0xFF);
}

我添加了 OCR_RANGE 和 OCR_ZERO，它们控制滤波输出的交流电压范围。范围：0-255。（OCR_RANGE = 256 可能会溢出）。OCR_ZERO 控制中间点（通常为 127），您应该在 setup() 中将初始 OCRA0 设置为 OCR_ZERO。

最后一点。声明正弦表时：

static uint8_t sin_B[65] =       //...  This gets store in data space, which is limited
static const uint8_t sin_B[65] = //... This gets stored on flash, which has plenty of room.

使正弦表尽可能大，中断尽可能快，确实可以对音质产生很大影响。

于 2017-07-05T16:41:10.763 回答