LPC2478的硬件IIC使用

LPC2478的IIC使用

LPC2478带有三个IIC接口,每个IIC都可以工作在主机或者从机模式下,LPC的IIC的架构是一种状态机的形式,在不同的的时间做不同的工作之后有不同的状态来表示,

简单来说,就是发送起始字节之后会有一个状态,接收到ACK之后会有一个状态,软件上根据已知的外设状态来进行下一步操作

具体的状态请查看数据手册,IIC的可用寄存器如下

对应不同的驱动方式,例如I2EN为1+STA为1,代表发送起始位+从机地址

将置位寄存器的数据清零,BIT一一对应

状态机的核心

数据发送缓存

从机地址,最高位读写位硬件自动加上

还有两个寄存器是SCL低电平占空比和高电平占空比,均为50%即可

具体代码如下所示

#ifndef __IIC0_H_

#define __IIC0_H_

#include "common.h"

#include "lpc24xx.h"

#include "clock.h"

#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

void IIC0Init(u32 baud);

u8 IIC0Start(void);

u8 IIC0SendWriteAddr(u8 addr);

u8 IIC0SendData(u8 data);

u8 IIC0SendStop(void);

u8 IIC0SendReadAddr(u8 addr);

u8 IIC0ReadData(u8* value,u8 ack);

u8 IIC0RepeatStart(void);

#endif

#include "iic.h"

#define I20EN  6		//接口使能

#define STA   5		//起始标志

#define STO   4		//停止标志

#define SI    3	    //中断标志

#define AA    2		//应答标志

#define I20ENC 6     //

#define STAC  5

#define SIC   3

#define AAC   2

#define STATE (I20STAT & 0xf8)

void IIC0Init(u32 baud)

{

    u32 t = (SystemCoreClock/4)/baud;

    //打开IIC时钟

    PCONP |= (1 << 7);

    //配置IIC引脚 sda

    PINSEL1 &= ~(0x03<<22);

    PINSEL1 |= (0x01<<22);

    PINMODE1 &= ~(0x03<<22);

    PINMODE1 |= (0x01<<22);

    //scl

    PINSEL1 &= ~(0x03<<24);

    PINSEL1 |= (0x01<<24);

    PINMODE1 &= ~(0x03<<24);

    PINMODE1 |= (0x01<<24);

    I20SCLL = t/2;

	I20SCLH = t/2;

    I20CONSET = (1<<I20EN);//接口使能

}

//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)

    {

        if(STATE == response)break;

    }

    if(retry)return 0;

    else return 1;

}

u8 IIC0Start(void)

{

    I20CONCLR = (1<<SIC)|(1<<STAC)|(1<<AAC);

	//Start

	I20CONSET = (1<<STA);

    return WaitResponse(STATUS_SENDSTART);

}

u8 IIC0RepeatStart(void)

{

    //repeat start

	I20CONCLR = (1<<SIC);

	I20CONSET = (1<<STA);

    return WaitResponse(STATUS_REPEATSTART);

}

u8 IIC0SendWriteAddr(u8 addr)

{

    //dev_addr

	I20DAT = addr;

	I20CONSET = (1<<AA);

	I20CONCLR = (1<<SIC)|(1<<STAC);

    return WaitResponse(STATUS_SENDSLAVE_ACK);

}

u8 IIC0SendData(u8 data)

{

    I20DAT = data;

	I20CONSET = (1<<AA);

	I20CONCLR = (1<<SIC);

    return WaitResponse(STATUS_SENDDATA_ACK);

}

u8 IIC0SendStop(void)

{

    I20CONCLR = (1<<SIC)|(1<<STAC)|(1<<AAC);

    I20CONSET = (1<<STO);

	I20CONCLR = (1<<SIC);

    return 0;

}

u8 IIC0SendReadAddr(u8 addr)

{

    I20DAT = addr;

	I20CONSET = (1<<AA);

	I20CONCLR = (1<<SIC)|(1<<STAC);

    return WaitResponse(STATUS_READADDR_ACK);

}

u8 IIC0ReadData(u8* value,u8 ack)

{

    if(ack)

    {

        I20CONSET = (1<<AA);

		I20CONCLR = (1<<SIC);

        if( WaitResponse(STATUS_RECV_ACK))return 1;

    }

    else

    {

        I20CONCLR = (1<<AAC)|(1<<SIC);

        if(WaitResponse(STATUS_RECV_NACK))return 1;

    }

    *value = I20DAT;

    return 0;

}