周五学习了I2C.周六在家弄了一天周四的作业。终于成功，收获颇多。先说一下周四一直不好使的原因：

Exclude from Simulation不能打挑，否则不参加模拟。所以周四一直没有成功。最后上程序。全部自己编写感觉最后4句非常简练。首次编写位操作程序，很成功。SPI  tc

#include<SPI.h>

const int slaveSelectPin = 10;

int A ;

int B ;

void setup() {

pinMode (slaveSelectPin, OUTPUT);

SPI.begin();

Serial.begin(9600);

digitalWrite(slaveSelectPin, HIGH);

SPI.transfer(0x80);

SPI.transfer(0x04);

digitalWrite(slaveSelectPin, LOW);

}

void loop() {

digitalWrite(slaveSelectPin, HIGH);

SPI.transfer(0x02);

A = SPI.transfer(0x00);

B = SPI.transfer(0x00);

digitalWrite(slaveSelectPin, LOW);

/*Serial.print((A&0b10000000)>>7);

Serial.print((A&0b01000000)>>6);

Serial.print((A&0b00100000)>>5);

Serial.print((A&0b00010000)>>4);

Serial.print((A&0b00001000)>>3);

Serial.print((A&0b00000100)>>2);

Serial.print((A&0b00000010)>>1);

Serial.println(A&0b00000001);*/

if(((A&0b01000000)>>6)==0)

Serial.println(A*2+B/32*0.25);

if(((A&0b01000000)>>6)==1)

Serial.println(-(((~A)&0b01111111)*2+2-B/32*0.25));

}