利用TWI与PCF8591通信读取AD采样值问题

2014-7-22 17:43

闲着蛋疼，Mega128本身自带AD，但是由于还处在学习阶段，于是用TWI与PCF8591进行通信，利用PCF8591读取ADC采样电压值，调节电位器，明明最大值是5V才对呀，可是扭开发板的电位器，电压从0V调节到2.5V，再变成0V，再往上调，最大才2.42V。调用的读函数用在24C02上可以正常读出数值。想了半天不知道哪里有问题。请高手帮忙看看！！！万分感谢，我是菜鸟初学者，还望高手不吝赐教

#include<iom128v.h>
#include<macros.h>
#pragma interrupt_handler timer1_ovf_isr:iv_TIM1_OVF

#define AddWr    0x90
#define AddRd    0x91

//MT模式：主机发送模式
#define START          0x08
#define RE_START          0x10
#define MT_SLA_ACK       0x18
#define MT_SLA_NOACK    0x20
#define MT_DATA_ACK       0x28
#define MT_DATA_NOACK 0x30

//MR模式：主机接收模式
#define START       0x08
#define RE_START 0x10
#define MR_SLA_ACK 0x40
#define MR_SLA_NOACK 0x48
#define MR_DATA_ACK 0x50
#define MR_DATA_NOACK 0x58

unsigned char TempData[];
unsigned char DuanMa[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,0x88,0x83,0xc6,0xa1,0x86,0x8e};
unsigned char WeiMa[]={0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80};

unsigned char ReadAdcFlag;

#define START_I2C() {TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);}
#define STOP_I2C() {TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);}
#define WAIT() {while (!(TWCR & (1<<TWINT)));}
#define TWI() {TWCR = (1<<TWINT)|(1<<TWEN);}
#define SendByte(X) {TWDR = X; TWCR = (1<<TWINT) | (1<<TWEN);}

void Delayus(unsigned int US)
{
   unsigned int i;
   US=US*5/4;
   for( i=0;i<US;i++);
}

void Delayms(unsigned int MS)
{
   unsigned int i,j;
   for( i=0;i<MS;i++)
   for(j=0;j<1141;j++);
}

void Led_init(void)
{
   DDRA = 0xff;
   DDRF |= (1 << 3);

   PORTA = 0xff;
   PORTF |= (1 << 3);
   PORTF &= ~(1 << 3);
}

void Seg_init(void)
{
   DDRA = 0xff;
   DDRC = 0xff;
   DDRF |= ((1 << 1) | (1 << 2));

   PORTC = 0xff;
   PORTF |= (1 << 1);
   PORTF &= ~(1 << 1);

   PORTA = 0xff;
   PORTF |= (1 << 2);
   PORTF &= ~(1 << 2);
}

void Seg_Display(unsigned char firstbit,unsigned char weishu)
{
   static unsigned char i;
   PORTC = 0xff;          //数码管消隐
   PORTF |= BIT(1);
   PORTF &= ~BIT(1);

   PORTC = TempData[i];
   PORTF |= BIT(1);
   PORTF &= ~BIT(1);

   PORTA = WeiMa[i+firstbit];
   PORTF |= BIT(2);
   PORTF &= ~BIT(2);
   Delayms(1);
   i++;
   if(i == weishu)
        i = 0;
}

unsigned char RevADC(unsigned char Channal)
{
unsigned char Val;

START_I2C(); //发出START 信号
WAIT(); //等待TWINT 置位， TWINT 置位表示START 信号已发出
if ((TWSR & 0xF8) != START) //检验TWI 状态寄存器，屏蔽预分频位，如果状态字不是START 转出错处理
   return 0;

SendByte(AddWr); //将SLA_W 载入TWDR 寄存器， TWINT位清零，启动发送地址
WAIT(); //等待TWINT 置位， TWINT 置位表示总线命令SLA+W 已发出，及收到应答信号ACK/NACK
if ((TWSR & 0xF8) != MT_SLA_ACK) //检验TWI 状态寄存器，屏蔽预分频位，如果状态字不是MT_SLA_ACK 转出错处理
   return 0;

SendByte(0x40 | Channal);
WAIT(); //等待TWINT 置位， TWINT 置位表示总线命令已发出，及收到应答信号ACK/NACK
if ((TWSR & 0xF8) != MT_DATA_ACK) //检验TWI 状态寄存器
   return 0;

START_I2C(); //发出START 信号
WAIT(); //等待TWINT 置位， TWINT 置位表示START 信号已发出
if ((TWSR & 0xF8) != RE_START) //检验TWI 状态寄存器，屏蔽预分频位，如果状态字不是START 转出错处理
   return 0;

SendByte(AddRd); //将SLA_W 载入TWDR 寄存器， TWINT位清零，启动发送地址
WAIT(); //等待TWINT 置位， TWINT 置位表示总线命令SLA+R 已发出，及收到应答信号ACK/NACK
if ((TWSR & 0xF8) != MR_SLA_ACK) //检验TWI 状态寄存器，屏蔽预分频位，如果状态字不是MR_SLA_ACK 转出错处理
   return 0;

TWI(); //启动主I2C读方式
WAIT(); //等待TWINT 置位,及收到应答信号ACK/NACK
if ((TWSR & 0xF8) != MR_DATA_NOACK)
   return 0;

Val = TWDR;
STOP_I2C();
return Val;
}

void Timer1_init(void)
{
   TCCR1B = 0x00; //stop
   TCNT1H = 0xFD; //setup
   TCNT1L = 0x8F;
   TCCR1B = 0x03; //start Timer
   TIMSK = 0x04; //timer interrupt sources
   SREG |= (1 << 7);
}

void main(void)
{
   unsigned int num;

   Led_init();
   Seg_init();
   Timer1_init();
   while(1)
     {
        num = RevADC(0);
   num = (num * 100 * 5)/255;

   TempData[0] = DuanMa[num / 100] & 0x7f;
   TempData[1] = DuanMa[(num % 100) / 10];
   TempData[2] = DuanMa[num % 100 % 10];
}
}

void timer1_ovf_isr(void)
{
   //TIMER1 has overflowed
   TCNT1H = 0xFD; //reload counter high value
   TCNT1L = 0x8F; //reload counter low value
   Seg_Display(0,3);
}