程序如下： void twi_init() {     TWBR = 0x02;     TWAR = 0xD1;     TWCR = 0x44;     TWSR = 0x00;    } uchar iic_write(uchar wdata, uchar addr) {     start();     wait();     if(test_ack()!=START) return 1;         write_8bit(WD_DEVICE_ADDR);     wait();     if(test_ack()!=MT_SLA_ACK) return 2;         write_8bit(wdata);     wait();     if(test_ack()!=MT_DATA_ACK) return 3;         write_8bit(addr);     wait();     if(test_ack()!=MT_DATA_ACK) return 4;         write_8bit(wdata);     wait();     if(test_ack() != MT_DATA_ACK) return 5;         stop();         return 0; } uchar iic_read(uchar addr) {     uchar temp;         start();        wait();     if((test_ack()!=START))        return 1;         write_8bit(WD_DEVICE_ADDR);     wait();        if(test_ack() != MT_SLA_ACK)     return 2;         write_8bit(addr);     wait();     if(test_ack()!=MT_DATA_ACK) return 3;         start();     wait();     if(test_ack()!= RE_START) return 4;         write_8bit(RD_DEVICE_ADDR+1);     wait();     if(test_ack() != MR_SLA_ACK) return 5;         twi();     wait();     if(test_ack()!= MR_DATA_NOACK) return 6;         temp = TWDR;         stop();     PORTC = 0x02;     return temp; } 用读函数读取数据的时候 都是返回 1