# 排燈，用 bit/byte 的方式表示圖案

用 bit 的方式來表示每排燈(也恰好為8個)的亮滅
- 節省記憶體
- 需了解 bit/Byte 之間的觀念
- 需熟悉 bit 的運算及邏輯

## 教學參考
- [Bit Math Tutorial by CosineKitty](https://playground.arduino.cc/Code/BitMath/)
- [Working with Bytes](https://www.thethingsnetwork.org/docs/devices/bytes.html)

## 基礎程式

#define PIN_TOTAL 8

int PIN_ARRAY[8] = {4, 5, 6, 7, 8, 9, 10, 11};  


void setup()
{
  for(int i=0; i<PIN_TOTAL; i++)
  {
    pinMode(PIN_ARRAY[i], OUTPUT);
  }
}


void led_bar(byte data)
{  
  for(int b=0; b<8; b++)
  {
    digitalWrite(PIN_ARRAY[b], data & (B10000000>>b));
  }
}


void loop()                     
{
  led_bar(B10101010);
  delay(500);
  led_bar(B01010101);  
  delay(500);
}

## 解說 bit 運算概念

參考下列範例，可檢查 serial monitor 的值。

#define PIN_TOTAL 8
int PIN_ARRAY[8] = {4, 5, 6, 7, 8, 9, 10, 11};  

void setup()
{
  for(int i=0; i<PIN_TOTAL; i++)
  {
    pinMode(PIN_ARRAY[i], OUTPUT);
  }
  Serial.begin(9600);
}


void led_bar(byte data)
{  
  Serial.println("");
  Serial.print(data);
  Serial.print("-->");
  Serial.print(data, BIN);
  Serial.print(": ");
  
  // 逐一取得各個位元
  digitalWrite(PIN_ARRAY[0], data & B10000000);
  digitalWrite(PIN_ARRAY[1], data & B01000000);
  digitalWrite(PIN_ARRAY[2], data & B00100000);
  digitalWrite(PIN_ARRAY[3], data & B00010000);
  digitalWrite(PIN_ARRAY[4], data & B00001000);
  digitalWrite(PIN_ARRAY[5], data & B00000100);
  digitalWrite(PIN_ARRAY[6], data & B00000010);
  digitalWrite(PIN_ARRAY[7], data & B00000001);
  
  // 由低位元往高位元
  /*
  for(int b=0; b<8; b++)
  {
    // digitalWrite(PIN_ARRAY[b], data & (B10000000>>b));
    
    if(data & (B10000000>>b))
    {
      Serial.print('1');
      digitalWrite(PIN_ARRAY[b], HIGH);
    }
    else
    {
      Serial.print('0');
      digitalWrite(PIN_ARRAY[b], LOW);
    }
  }
  */
}


void loop()                     
{
  int u= 200;
  
  led_bar(B10000000);  delay(u);
  led_bar(B01000000);  delay(u);
  led_bar(B00100000);  delay(u);
  led_bar(B00010000);  delay(u);
  led_bar(B00001000);  delay(u);
  led_bar(B00000100);  delay(u);
  led_bar(B00000010);  delay(u);
  led_bar(B00000001);  delay(u);
}

## 應用：更多樣變化

#define PIN_TOTAL 8
int PIN_ARRAY[8] = {4, 5, 6, 7, 8, 9, 10, 11};  

int u = 100;

void setup()
{
  for(int i=0; i<PIN_TOTAL; i++)
  {
    pinMode(PIN_ARRAY[i], OUTPUT);
  }
}

void led_bar(byte data)
{  
  for(int b=0; b<8; b++)
  {
    digitalWrite(PIN_ARRAY[b], data & (B10000000>>b));
  }
}

void loop()
{
  for(int i=0; i<10; i++) { type1(); }
  for(int i=0; i<3 ; i++) { type2(); }
  for(int i=0; i<5 ; i++) { type3(); }
  for(int i=0; i<5 ; i++) { type4(); }
  for(int i=0; i<8 ; i++) { type5(); }
  for(int i=0; i<5 ; i++) { type6(); }
  for(int i=0; i<10; i++) { type7(); }
  for(int i=0; i<10; i++) { type8(); }
  for(int i=0; i<10; i++) { type9(); }
}

void type1()
{
  led_bar(B10101010);  delay(u);
  led_bar(B01010101);  delay(u);
}

void type2()
{
  led_bar(B10000000);  delay(u);
  led_bar(B01000000);  delay(u);
  led_bar(B00100000);  delay(u);
  led_bar(B00010000);  delay(u);
  led_bar(B00001000);  delay(u);
  led_bar(B00000100);  delay(u);
  led_bar(B00000010);  delay(u);
  led_bar(B00000001);  delay(u);
  led_bar(B00000010);  delay(u);
  led_bar(B00000100);  delay(u);
  led_bar(B00001000);  delay(u);
  led_bar(B00010000);  delay(u);
  led_bar(B00100000);  delay(u);
  led_bar(B01000000);  delay(u);
  led_bar(B10000000);  delay(u);
}

void type3()
{
  led_bar(B11111111);  delay(u);
  led_bar(B00000000);  delay(u);
}

void type4()
{
  led_bar(B11100000); delay(u);
  led_bar(B01110000); delay(u);
  led_bar(B00111000); delay(u);
  led_bar(B00011100); delay(u);
  led_bar(B00001110); delay(u);
  led_bar(B00000111); delay(u);
  led_bar(B10000011); delay(u);
  led_bar(B11000001); delay(u);
}

void type5()
{
  led_bar(B10000001); delay(u);
  led_bar(B01000010); delay(u);
  led_bar(B00100100); delay(u);
  led_bar(B00011000); delay(u);
  led_bar(B00100100); delay(u);
  led_bar(B01000010); delay(u);
}

void type6()
{
  led_bar(B00000000); delay(u);
  led_bar(B10000001); delay(u);
  led_bar(B11000011); delay(u);
  led_bar(B11100111); delay(u);
  led_bar(B11111111); delay(u);
  led_bar(B01111110); delay(u);
  led_bar(B00111100); delay(u);
  led_bar(B00011000); delay(u);
}
  
void type7()
{
  led_bar(B00000000); delay(u);
  led_bar(B11111111); delay(u);
}

void type8()
{
  led_bar(B11001100); delay(u);
  led_bar(B00110011); delay(u);
}

void type9()
{
  led_bar(B11110000); delay(u);
  led_bar(B00001111); delay(u);
}