EK-TM4C123GXL i2c总线

void IIC_INIT(void)
{
SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C1);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

GPIOPinConfigure(GPIO_PA6_I2C1SCL);
GPIOPinConfigure(GPIO_PA7_I2C1SDA);
GPIOPinTypeI2C(GPIO_PORTA_BASE,GPIO_PIN_7);
GPIOPinTypeI2CSCL(GPIO_PORTA_BASE,GPIO_PIN_6);

// 语句的最后一个参数是用来设定数据传输速率的。
// false表示传输速率是100kbps，true则意味着传输速率是400kbps。
//此处使用的是100kbps的传输速率
I2CMasterInitExpClk(I2C1_BASE, SysCtlClockGet(), 0);
I2CMasterEnable(I2C1_BASE);
}
int i2c_write(unsigned char slave_addr,
unsigned char reg_addr,
unsigned char length,
unsigned char const *data)
{
//设置I2C1主模块将要放在总线上的从模块地址
//false代表主模块发送，从模块接收
unsigned char i;
if(0 == length)
{
return -1;
}
I2CMasterSlaveAddrSet(I2C1_BASE, slave_addr, false);
I2CMasterDataPut(I2C1_BASE, reg_addr);
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_START);
while(I2CMasterBusy(I2C1_BASE))
{
}
// 主模块开始发送寄存器地址
for(i=0; i<length; i++)
{
I2CMasterDataPut(I2C1_BASE, data[i]);
// 主模块开始发送数据
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_CONT);
while(I2CMasterBusy(I2C1_BASE))
{
}
}
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_STOP);
while(I2CMasterBusy(I2C1_BASE))
{
}
return 0;
}

int i2c_read(unsigned char slave_addr,
unsigned char reg_addr,
unsigned char length,
unsigned char *data)
{
if(0 == length)
return -1;
if(1 == length)
{
I2CMasterSlaveAddrSet(I2C1_BASE, slave_addr, false);
I2CMasterDataPut(I2C1_BASE, reg_addr);
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_START);
while(I2CMasterBusy(I2C1_BASE))
{
}
I2CMasterSlaveAddrSet(I2C1_BASE, slave_addr, true);
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);
while(I2CMasterBusy(I2C1_BASE))
{
}
data[0] = I2CMasterDataGet(I2C1_BASE);
}
else
{
unsigned char i;
I2CMasterSlaveAddrSet(I2C1_BASE, slave_addr, false);
I2CMasterDataPut(I2C1_BASE, reg_addr);
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_START);
while(I2CMasterBusy(I2C1_BASE))
{
}
I2CMasterSlaveAddrSet(I2C1_BASE, slave_addr, true);
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_RECEIVE_START);
while(I2CMasterBusy(I2C1_BASE))
{
}
data[0] = I2CMasterDataGet(I2C1_BASE);
for(i=1; i<length-1; i++)
{

I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_RECEIVE_CONT);
while(I2CMasterBusy(I2C1_BASE))
{
}
data[i] = I2CMasterDataGet(I2C1_BASE);
}
I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_RECEIVE_FINISH);
while(I2CMasterBusy(I2C1_BASE))
{
}
data[i] = I2CMasterDataGet(I2C1_BASE);
}
return 0;
}

///******main

InitUart0();
IIC_INIT();
//UARTSend("s",1);
while(1)
{
//I2CMasterSlaveAddrSet(I2C1_BASE, 0xD2, false);
//I2CMasterDataPut(I2C1_BASE, 0x0f);
//I2CMasterControl(I2C1_BASE, I2C_MASTER_CMD_BURST_SEND_START);

i2c_read(0xD2,0x0f,1,data);
UARTSend(data,1);
delay_ms(10);
}

结果示波器上第一个字节只显示了7位数据。。

求解！！！！！