LPC1768有三路IIC,其中IIC0支持高速模式和plus模式,另外两路是普通IIC,使用IIC的过程如下

首先依然是打开IIC时钟,同时打开GPIO时钟

然后配置引脚为IIC功能

另外,因为iic0支持plus结构,所以gpio控制的时候还有这个寄存器需要设置

接下来设置IIC的高低电平占空比

最后使能接口就可以使用了

初始化示例代码如下

void IIC0Init(u32 baud)

{

u32 t = (SystemCoreClock/4)/baud;

//打开IIC时钟

LPC_SC->PCONP |= (1 << 7);

LPC_SC->PCONP |= (1<<15);//gpio 时钟

//配置IIC引脚 sda

LPC_PINCON->PINSEL1 &= ~(0x03<<22);

LPC_PINCON->PINSEL1 |= (0x01<<22);

LPC_PINCON->PINMODE1 &= ~(0x03<<22);

LPC_PINCON->PINMODE1 |= (0x01<<22);

LPC_PINCON->PINMODE_OD0 |= 0x01<<27;

//scl

LPC_PINCON->PINSEL1 &= ~(0x03<<24);

LPC_PINCON->PINSEL1 |= (0x01<<24);

LPC_PINCON->PINMODE1 &= ~(0x03<<24);

LPC_PINCON->PINMODE1 |= (0x01<<24);

LPC_PINCON->PINMODE_OD0 |= 0x01<<28;

LPC_PINCON->I2CPADCFG = 0x0;

LPC_I2C0->I2SCLL = t/2;

LPC_I2C0->I2SCLH = t/2;

LPC_I2C0->I2CONSET = (1<<I2EN);//接口使能

}

LPC的IIC使用起来是依靠状态组合来判定传输状态的,而不是像其他单片机依靠标志位识别,

每次控制设备执行一个动作之后检测返回的状态位对不对,就可以判定传输是否成功,相应的传送代码如下

//等待指定的状态

//失败返回1 成功返回0

u8 WaitResponse(u8 response)

{

u8 retry = 200;

while(--retry)

{

DelayUs(1);

if(STATE == response)break;

}

if(retry)return 0;

else return 1;

}

u8 IIC0Start(void)

{

LPC_I2C0->I2CONCLR = (1<<SIC)|(1<<STAC)|(1<<AAC);

//Start

LPC_I2C0->I2CONSET = (1<<STA);

return WaitResponse(STATUS_SENDSTART);

}

u8 IIC0RepeatStart(void)

{

//repeat start

LPC_I2C0->I2CONCLR = (1<<SIC);

LPC_I2C0->I2CONSET = (1<<STA);

return WaitResponse(STATUS_REPEATSTART);

}

u8 IIC0SendWriteAddr(u8 addr)

{

//dev_addr

LPC_I2C0->I2DAT = addr;

LPC_I2C0->I2CONSET = (1<<AA);

LPC_I2C0->I2CONCLR = (1<<SIC)|(1<<STAC);

return WaitResponse(STATUS_SENDSLAVE_ACK);

}

u8 IIC0SendData(u8 data)

{

LPC_I2C0->I2DAT = data;

LPC_I2C0->I2CONSET = (1<<AA);

LPC_I2C0->I2CONCLR = (1<<SIC);

return WaitResponse(STATUS_SENDDATA_ACK);

}

u8 IIC0SendStop(void)

{

LPC_I2C0->I2CONCLR = (1<<SIC)|(1<<STAC)|(1<<AAC);

LPC_I2C0->I2CONSET = (1<<STO);

LPC_I2C0->I2CONCLR = (1<<SIC);

return 0;

}

u8 IIC0SendReadAddr(u8 addr)

{

LPC_I2C0->I2DAT = addr;

LPC_I2C0->I2CONSET = (1<<AA);

LPC_I2C0->I2CONCLR = (1<<SIC)|(1<<STAC);

return WaitResponse(STATUS_READADDR_ACK);

}

u8 IIC0ReadData(u8* value,u8 ack)

{

if(ack)

{

LPC_I2C0->I2CONSET = (1<<AA);

LPC_I2C0->I2CONCLR = (1<<SIC);

if( WaitResponse(STATUS_RECV_ACK))return 1;

}

else

{

LPC_I2C0->I2CONCLR = (1<<AAC)|(1<<SIC);

if(WaitResponse(STATUS_RECV_NACK))return 1;

}

*value = LPC_I2C0->I2DAT;

return 0;

}

返回的状态代码在系统中的定义为

#define STATUS_SENDSTART        0X08

#define STATUS_REPEATSTART      0X10

#define STATUS_SENDSLAVE_ACK    0X18

#define STATUS_SENDSLAVE_NACK   0X20

#define STATUS_SENDDATA_ACK     0X28

#define STATUS_SENDDATA_NACK    0X30

#define STATUS_LOSS             0X38

#define STATUS_READADDR_NACK    0X48

#define STATUS_READADDR_ACK     0X40

#define STATUS_RECV_ACK         0X50

#define STATUS_RECV_NACK        0X58

通过这一套api就可以完成iic通讯,以下是eeprom的例子

u8 At24cxxWriteBuffer(u16 writeAddr,u8* bufferStart,u8 len)

{

u8 ret = 0;

u8 i = 0;

ret = HwIIC1Start();    //  发送开始条件

if(ret)return 1;

if(EE_TYPE > AT24C16)

{

ret = HwIIC1SendWriteAddr(AT_DEVICE_ADDR);  //发送器件地址

if(ret)return 1;

ret = HwIIC1SendData((u8)writeAddr>>8); //发送高八位地址

if(ret)return 1;

}

else

{

ret = HwIIC1SendWriteAddr(AT_DEVICE_ADDR+((writeAddr/256)<<1));   //发送器件地址0XA0,写数据

if(ret)return 1;

}

ret = HwIIC1SendData((u8)writeAddr);    //发送低八位地址

if(ret)return 1;

for(i = 0; i < len; i++)

{

ret = HwIIC1SendData(*(bufferStart+i)); //发送数据

if(ret)return 1;

}

HwIIC1SendStop();   //发送停止位

DelayMs(5); //5ms等待写入完成

return 0;

}

u8 At24cxxReadBuffer(u16 readAddr,u8* bufferStart,u8 len)

{

u8 ret = 0;

u8 i = 0;

ret = HwIIC1Start();    //  发送开始条件

if(ret)return 1;

if(EE_TYPE > AT24C16)

{

ret = HwIIC1SendWriteAddr(AT_DEVICE_ADDR);  //发送器件地址

if(ret)return 1;

ret = HwIIC1SendData((u8)readAddr>>8);  //发送高八位地址

if(ret)return 1;

}

else

{

ret = HwIIC1SendWriteAddr(AT_DEVICE_ADDR+((readAddr/256)<<1));   //发送器件地址0XA0,写数据

if(ret)return 1;

}

ret = HwIIC1SendData((u8)readAddr); //发送低八位地址

if(ret)return 1;

ret = HwIIC1RepeatStart();  //重发start

if(ret)return ret;

ret = HwIIC1SendReadAddr(AT_DEVICE_ADDR+1);           //进入接收模式

if(ret)return ret;

for(i = 0; i < len-1; i++)

{

ret = HwIIC1ReadData(bufferStart+i,1);  //发送ACK

if(ret)return ret;

}

ret = HwIIC1ReadData(bufferStart+len-1,0);//读取不发送ACK

if(ret)return ret;

HwIIC1SendStop();//产生一个停止条件

return 0;

}