TWI ATMEGA16L 丛机模式

#define SLAVE_ADDRESS  0x05

#define SCL               0
#define SDA               1
#define TWI_PORT          PORTC
#define TWI_DIR           DDRC

//SLAVE RECEIVE MODE
#define SR_SLA_ACK        0X60//从机接收地址响应
#define SR_SLA_FAIL       0X68//作为主机仲裁失败，自己的ALT+W被接收
#define SR_GCA_ACK        0X70//从机接收广播响应
#define SR_GCA_FAIL       0X78//作为主机仲裁失败，接收到广播地址
#define SR_DATA_ACK       0X80//从机接收数据响应
#define SR_DATA_NACK      0X88//从机接收数据非应答
#define SR_GCA_DATA_ACK   0X90//从机接收广播数据应答
#define SR_GCA_DATA_NACK  0X98//从机接收广播数据非应答
#define SR_STOP_RESTART   0xA0//从机工作时收到STOP或RESTART
//SLAVE SEND MODE
#define ST_SLA_ACK        0XA8//从机发送地址应答
#define ST_SLA_FAIL       0XB0//作为主机仲裁失败，自己的ALT+R被接收
#define ST_DATA_ACK       0XB8//从机发送数据应答
#define ST_DATA_NACK      0XC0//从机发送数据非应答
#define ST_BYTE_ACK       0XC8//数据已发送，接收到ACK

#define ILLEGAL     0x00

#define TWI_ACK()         (TWCR = (1< #define TWI_NOACK()       (TWCR = (1< #define TWI_RESUME()      (TWCR = (1<

//全局变量
//volatile unsigned char transmit_ready = 0;
volatile unsigned char receive_ready = 0;
//局部变量
static unsigned char transmit_leng = 0;
static unsigned char receive_leng = 0;

static struct SR sr_temp;

void IIC_Init(void)
{
    PORTC |= (1<  DDRC &= ~((1<     
 TWCR = 0x00;
 
  TWAR = (SLAVE_ADDRESS<<1)|(0x00);
 TWDR = 0x00;
 TWCR = (1<  
 st.start = 0x5A;
 
    transmit_leng = sizeof(st);
 receive_leng = sizeof(sr);
}

#pragma interrupt_handler TWI_ISR:18
void TWI_ISR(void)
{
    static unsigned char transmit_cnt = 0;
 static unsigned char receive_cnt = 0;
 
 unsigned char *p_st = (unsigned char *)&st;
 unsigned char *p_sr = (unsigned char *)&sr_temp;
 static unsigned char check = 0;    //校验和
 
    SREG &= ~0x80;
  
    if (sleep_mode == POWER_DOWN)
    {
        sys_reset_flag = 1;
    }
 
 switch(TWSR&0xf8) 
 {
     case SR_SLA_ACK:  
  case 68:
      receive_cnt = 0;                            
      TWI_ACK();
   break;
  case SR_DATA_ACK:   
   if (receive_cnt < (receive_leng-1))
   {
       *(p_sr+receive_cnt) = TWDR;
   }
   else if (receive_cnt == (receive_leng-1))
   {
       *(p_sr+receive_cnt) = TWDR;
    receive_ready = 1;
   }
   receive_cnt++;
   TWI_ACK(); 
   break;
        case SR_STOP_RESTART:                              // 0xA0:从机工作时收到STOP或RESTART      
   TWI_ACK();
   break;
   
  case ST_SLA_ACK:                                   // 0XA8:从机发送地址应答
   transmit_cnt = 0;
   TWDR = *(p_st+transmit_cnt);
   check = *(p_st+transmit_cnt);
   transmit_cnt++;
      TWI_ACK(); 
   break; 
  case ST_DATA_ACK:                                  // 0XB8:从机发送数据应答 
      if (transmit_cnt < (transmit_leng-1))
   {
       TWDR = *(p_st+transmit_cnt);
    check += *(p_st+transmit_cnt);    
   }
   else if (transmit_cnt == (transmit_leng-1))
   {
       TWDR = check;   //发送校验和
   }
   transmit_cnt++;
   TWI_ACK();
   break;
  case ST_DATA_NACK:
      //transmit_ready = 1;
   TWI_ACK();
   break; 
  case ILLEGAL:
  case 0xF8:  
   TWI_RESUME();
   break;
 } 
 SREG |= 0x80;
}