和爷爷一起学Arduino四联MAX7219（继续学习面向对象编程OOP）

　　MAX7219是通过SPI总线交换信息的，因此，多个MAX7219可以级联。这里就是四个MAX7219级联，分别显示1、2、3、4。下面是代码示例。
　　首先要include三个头文件：SPI.h、Adafruit_GFX.h、Max72xxPanel.h。然后按照Max72xxPanel库里的类Max72xxPanel定义一个对象myMatrix，三个数据成员的初始值为9、4、1，依次为片选所接的端口号、显示点阵的水平屏数和垂直屏数。接着是一个8个元素的数组LEDArray[]，用来描述哪些点是亮的，哪些是暗的。下面，对象myMatrix的成员函数drawPixel()就是将数组里的值映射到显示点阵。这只是建立映射，后面的另一个成员函数write()才是真正点亮显示点阵。#include  #include  #include   Max72xxPanel myMatrix = Max72xxPanel(9,4,1); uint8_t  LEDArray[8];  const uint8_t LedArray0[8] PROGMEM ={0x3c,0x18,0x18,0x18,0x18,0x18,0x1c,0x18}; const uint8_t LedArray1[8] PROGMEM ={0x7e,0x04,0x08,0x10,0x20,0x40,0x42,0x3c}; const uint8_t LedArray2[8] PROGMEM ={0x38,0x44,0x40,0x30,0x30,0x40,0x44,0x38}; const uint8_t LedArray3[8] PROGMEM ={0x20,0x20,0xff,0x22,0x24,0x28,0x30,0x20};  void setup(){  }  void loop(){   memcpy_P(&LEDArray, &LedArray0, 8);   for(int index_i=0; index_i<8; index_i++)   {     for(int index_j=0*8; index_j<0*8+8; index_j++)     {       if((LEDArray[index_i]&0x01)>0)         myMatrix.drawPixel(index_j, 7-index_i,1);       else         myMatrix.drawPixel(index_j, 7-index_i,0);       LEDArray[index_i] = LEDArray[index_i]>>1;     }   }   myMatrix.write();   memcpy_P(&LEDArray, &LedArray1, 8);   for(int index_i=0; index_i<8; index_i++)   {     for(int index_j=1*8; index_j<1*8+8; index_j++)     {       if((LEDArray[index_i]&0x01)>0)         myMatrix.drawPixel(index_j, 7-index_i,1);       else         myMatrix.drawPixel(index_j, 7-index_i,0);       LEDArray[index_i] = LEDArray[index_i]>>1;     }   }   myMatrix.write();   memcpy_P(&LEDArray, &LedArray2, 8);   for(int index_i=0; index_i<8; index_i++)   {     for(int index_j=2*8; index_j<2*8+8; index_j++)     {       if((LEDArray[index_i]&0x01)>0)         myMatrix.drawPixel(index_j, 7-index_i,1);       else         myMatrix.drawPixel(index_j, 7-index_i,0);       LEDArray[index_i] = LEDArray[index_i]>>1;     }   }   myMatrix.write();   memcpy_P(&LEDArray, &LedArray3, 8);   for(int index_i=0; index_i<8; index_i++)   {     for(int index_j=3*8; index_j<3*8+8; index_j++)     {       if((LEDArray[index_i]&0x01)>0)         myMatrix.drawPixel(index_j, 7-index_i,1);       else         myMatrix.drawPixel(index_j, 7-index_i,0);       LEDArray[index_i] = LEDArray[index_i]>>1;     }   }   myMatrix.write(); }