[转][精]s3c2440的A/D转换应用

s3c2440的A/D转换应用

 

       A/D转换，又称为模数转换，是将模拟信号转换为计算机能够处理的数字信号。s3c2440集成了8通道10位CMOS A/D转换器。

 

       对于s3c2440来说，实现A/D转换比较简单，主要应用的是ADC控制寄存器ADCCON和ADC转换数据寄存器ADCDAT0。寄存器ADCDAT0的低10位用于存储A/D转换后的数据。寄存器ADCCON的第15位用于标识A/D转换是否结束。第14位用于使能是否进行预分频，而第6位到第13位则存储的是预分频数值，因为A/D转换的速度不能太快，所以要通过预分频处理才可以得到正确的A/D转换速度，如我们想要得到A/D转换频率为1MHz，则预分频的值应为49。第3位到第5位表示的是A/D转换的通道选择。第2位可以实现A/D转换的待机模式。第1位用于是否通过读取操作来使能A/D转换的开始。第0位则是在第1位被清零的情况下用于开启A/D转换。

 

       下面我们就给出一个A/D转换的实例。我们在AIN2引脚上接了一个温度传感器，被检测的温度范围为0度~99度，它对应于A/D转换数据的0~0x3FF。检测到的温度被实时地显示在LCD上，这里我们只显示温度的整数部分。由于要实时显示数据，因此就涉及到LCD刷新的问题，如果处理得不好，会出现LCD闪烁的现象。所以在程序中，我们只对要刷新的区域进行刷新处理，而对其他区域不更新，这样就有效地防止了LCD的闪烁。

 

 

……  ……

unsigned char degree[]=                      //℃                48×48字模

{

……  ……

};

unsigned char colon[]=                       //：                48×48字模

{

……  ……

};

unsigned char du[]=                            //度                48×48字模

{

……  ……

};

unsigned char wen[]=                         //温                48×48字模

{

……  ……

};

unsigned char digital[]=                      //0~9的ASCII码字符数组                24×48字模

{

……  ……

};

 

//重新改写刷屏的程序，确定了要刷屏的区域范围

void Brush_Background( int x,int y,int width,int height,U32 c)

{

       int i,j ;

             

for( j = y ; j

       {

       for( i = x ; i < width ; i++ )

              {

                     LCD_BUFFER[j][i] = c ;

       }

       }

}

 

int readADC(void)

{

       rADCCON = (1<<14)|(49<<6)|(2<<3);              //设置预分频器和A/D通道

      

       rADCCON|=0x1;                                      //启动A/D转换

 

       while(rADCCON & 0x1)

              ;                                                //确认A/D转换是否开始

       while(!(rADCCON & 0x8000))

              ;                                                //等待A/D转换的结束

 

       return ( (int)rADCDAT0 & 0x3ff );      //读取A/D转换的数据

}

 

void Main(void)

{

       int temperature,oldTemp;

       unsigned char value[2],oldValue;

 

LCD_Init();   

       rLCDCON1|=1;

   

Brush_Background(0,0,LCD_WIDTH,LCD_HEIGHT,0xFFFFFF);          //刷写这个LCD

       Draw_Text48(16,96,0xff0000,wen)  ;

Draw_Text48(64,96,0xff0000,du)  ;

       Draw_Text48(112,96,0xff0000,colon)  ;

Draw_Text48(208,96,0xff0000,degree)  ;

 

oldTemp=0;

       oldValue=0;

  

while(1)

       {

          

       temperature = (int)readADC()*99/0x3ff;                   //读取温度

              if(oldTemp != temperature)                        //判断温度是否有变化

       {

                     oldTemp = temperature;

                    

                     value[0] = (unsigned char)temperature/10;                 //温度的十位数据

              value[1] = (unsigned char)temperature%10;               //温度的个位数据

                     if(oldValue!=value[0])                        //十位数据没有变化就不需要更新

              {

                            oldValue=value[0];

                     Brush_Background(150,96,150+24,96+48,0xFFFFFF);             //刷新十位数据的区域

                            Draw_ASCII(150,96,0xff0000,digital+144*value[0]);                     //显示十位数据

              }

                     Brush_Background(174,96,174+24,96+48,0xFFFFFF);                    //刷新个位数据区域

              Draw_ASCII(174,96,0xff0000,digital+144*value[1]);                            //显示个位数据

              }

       delay(1000000);

       }

}

 

 

 

既然可以上传图片了，我就把LCD显示的结果给大家展示一下！

 

 

 

 

 

鉴于有一些网友向我索要Draw_Text48函数和Draw_ASCII函数，那么我就索性把它们也贴出来。

 

void PutPixel(U32 x,U32 y, U32 c )

{

LCD_BUFFER[y][x] = c;

}

 

//48*48

void Draw_Text48(U32 x,U32 y,U32 color,unsigned char ch[])

{

       unsigned short int i,j;

       unsigned char mask,buffer;

      

       for(i=0;i<48;i++)

       {

              mask=0x80;

              buffer=ch[i*6];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j,y+i,color);

                     }

                     mask=mask>>1;                  

              }

              mask=0x80;

              buffer=ch[i*6+1];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+8,y+i,color);

                     }

                     mask=mask>>1;                  

              }

             

              mask=0x80;

              buffer=ch[i*6+2];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+16,y+i,color);

                     }

                     mask=mask>>1;                  

              }

              mask=0x80;

              buffer=ch[i*6+3];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+24,y+i,color);

                     }

                     mask=mask>>1;                  

              }

             

              mask=0x80;

              buffer=ch[i*6+4];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+32,y+i,color);

                     }

                     mask=mask>>1;                  

              }

              mask=0x80;

              buffer=ch[i*6+5];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+40,y+i,color);

                     }

                     mask=mask>>1;                  

              }

       }

}

 

//24*48 for ASCII

void Draw_ASCII(U32 x,U32 y,U32 color,const unsigned char ch[])

{

       unsigned short int i,j;

       unsigned char mask,buffer;

      

       for(i=0;i<48;i++)

       {

              mask=0x80;

              buffer=ch[i*3];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j,y+i,color);

                     }

                     mask=mask>>1;                  

              }

             

              mask=0x80;

              buffer=ch[i*3+1];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+8,y+i,color);

                     }

                     mask=mask>>1;                  

              }

             

              mask=0x80;

              buffer=ch[i*3+2];

              for(j=0;j<8;j++)

              {

                    

                     if(buffer&mask)

                     {

                            PutPixel(x+j+16,y+i,color);

                     }

                     mask=mask>>1;                  

              }

       }

}

 

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/zhaocj/archive/2010/04/17/5495730.aspx

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