S3C2440模擬IIC方式操作EEPROM

在S3C2440下，編寫iic程序，可以有一下三種方法，其實就是2種：

1.自己編寫模擬iic程序，控制IO口的變化。

2.使用驅動本身帶的模擬iic程序，也就是bit-banging。

3.使用硬件iic，這不在我的討論范圍之內，有時間也可以補充上來。

我目前使用的是在linux操作系統(tǒng)上實現(xiàn)的代碼:

貼出實現(xiàn)的代碼(不使用內核中的模擬iic程序):

第一部分是驅動層的代碼:

1.EEPROM.c代碼:

********************copyright by wit_yuan 2016-09-17 at beijing 龍興園北區(qū)**/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include



#define SDA_DELAY 5
#define SCL_DELAY 5

/*
*
* 本函數(shù)是操作在S3C2440上的GPIO模擬IIC程序，不使用內核提供的模擬GPIO操作，也就是不調用:
* i2c-dev.c,i2c-algo-bit.c,i2c-core.c,i2c-gpio.c文件的內容。
*
* 在開發(fā)板上找到兩個引腳，SCL,SDA如下所示:
* IICSCL GPE14
* IICSDA GPE15
*
*/
/*
*
* 操作思路:(具體可以參考STM32的模擬IIC來做)
* 1.使用基本的文件讀寫操作方法，為應用層提供基本的open,read,write函數(shù)。
* 2.提供基本的設備注冊，類注冊方法。
*
* GPECON:0x56000040 GPE15[31:30] 00-input,01-output 10-IICSDA GPE14[29:28] 10-IICSCL
* GPEDAT:0x56000044 GPE15[15:0]
* GPEUP :0x56000048
*
*
*/
struct device *g_p_device;
struct class *g_p_class;
static int g_major;
static volatile unsigned int *GPECON;
static volatile unsigned int *GPEDAT;

#define SDA_OUT() do{*GPECON &= ~(0x3 << 30); *GPECON |= (1<<30);} while(0);
#define SDA_IN() do{*GPECON &= ~(0x3 << 30);} while(0);
#define READ_SDA ((*GPEDAT)&(1<<15))

#define SCL_INIT() do{*GPECON &= ~(0x3 << 28); *GPECON |= (1<<28);} while(0);
#define SDA_INIT() do{*GPECON &= ~(0x3 << 30); *GPECON |= (1<<30);} while(0);


#define EEPROM_MAGIC m
#define EEPROM_WRITE _IOW(EEPROM_MAGIC,0,int)
#define EEPROM_READ _IOR(EEPROM_MAGIC,1,int)

#define IIC_SDA(a)
do{
if(a==0){
*GPEDAT &= ~(1<<15);
}
else
{
*GPEDAT |= (1<<15);
}
}while(0);

#define IIC_SCL(a)
do{
if(a==0){
*GPEDAT &= ~(1<<14);
}
else
{
*GPEDAT |= (1<<14);
}
}while(0);

typedef struct IIC_Struct{
unsigned char u_device_address;
unsigned char u_reg_address;

}T_IIC_Struct;

static T_IIC_Struct g_t_iic_struct;

static void IIC_Init(void)
{
SCL_INIT();
SDA_INIT();

//開啟設置初始狀態(tài)
IIC_SDA(1);
udelay(SDA_DELAY);

IIC_SCL(1);
udelay(SCL_DELAY);
}


/**
*
* 這部分是EEPROM的模擬IIC的實現(xiàn)部分。需要仔細
*
*
*
*
*
*
*/
void IIC_Start(void)
{
SDA_OUT();
IIC_SDA(1);
udelay(SDA_DELAY);

IIC_SCL(1);
udelay(SCL_DELAY);

IIC_SDA(0);
udelay(SDA_DELAY);

IIC_SCL(0);
udelay(SCL_DELAY);
}


void IIC_Stop(void )
{
SDA_OUT();

IIC_SDA(0);
udelay(SDA_DELAY);

IIC_SCL(1);
udelay(SCL_DELAY);

IIC_SDA(1);
udelay(SDA_DELAY);
}

unsigned char IIC_Wait_Ack(void)
{
unsigned short ucErrTime=0;

IIC_SCL(0);
udelay(SCL_DELAY);

SDA_IN(); //SDA設置為輸入

while(READ_SDA)
{
ucErrTime++;
if(ucErrTime>250)
{
IIC_Stop();
return 1; //超時，表明數(shù)據傳輸有問題
}
}
IIC_SCL(1);
udelay(SCL_DELAY);

IIC_SCL(0);//時鐘輸出0
udelay(SCL_DELAY);

return 0;
}

//產生ACK應答
void IIC_Ack(void)
{
IIC_SCL(0);
udelay(SCL_DELAY);

//added by wit_yuan 2016-09-16
SDA_OUT();
IIC_SDA(1);
udelay(SDA_DELAY);


IIC_SDA(0);
udelay(SDA_DELAY);


IIC_SCL(1);
udelay(SCL_DELAY);
IIC_SCL(0);
udelay(SCL_DELAY);

//////add 2016-09-16 by wit_yuan///////////
IIC_SDA(1);
udelay(SDA_DELAY);
}

//不產生ACK應答
void IIC_NAck(void)
{
SDA_OUT();
IIC_SCL(0);
udelay(SCL_DELAY);

IIC_SDA(1);
udelay(SDA_DELAY);

IIC_SCL(1);
udelay(SCL_DELAY);
IIC_SCL(0);
udelay(SCL_DELAY);
}

void IIC_Send_Byte(unsigned char txd)
{
unsigned char t;
SDA_OUT();
IIC_SCL(0);//拉低時鐘開始數(shù)據傳輸
udelay(SCL_DELAY);
for(t=0;t<8;t++)
{
if((txd&0x80)>>7)
{
IIC_SDA(1);
}
else
{
IIC_SDA(0);
}
txd<<=1;
udelay(SDA_DELAY);
IIC_SCL(1);
udelay(SCL_DELAY);
IIC_SCL(0);
udelay(SCL_DELAY);
}
}

//讀1個字節(jié)，ack=1時，發(fā)送ACK，ack=0，發(fā)送nACK
unsigned char IIC_Read_Byte( void )
{
unsigned char i,u_receive=0;
SDA_IN();//SDA設置為輸入
for(i=0;i<8;i++ )
{
IIC_SCL(0);
udelay(SCL_DELAY);
IIC_SCL(1);
udelay(SCL_DELAY);
u_receive<<=1;
if(READ_SDA)
u_receive++;
}

return u_receive;
}


ssize_t EEPROM_Write(struct file *p_file, const char __user *p_buf, size_t len, loff_t *p_lof)
{


unsigned int i;
unsigned int i_err = 0;

unsigned char *p_buffer;


if(len <= 0)
return 0;

p_buffer = kzalloc(sizeof(char) * len, GFP_KERNEL);
copy_from_user(p_buffer,p_buf,len);

printk("----EEPROM write device-----n");

IIC_Start();
IIC_Send_Byte(g_t_iic_struct.u_device_address << 1);
i_err |= IIC_Wait_Ack();

IIC_Send_Byte(g_t_iic_struct.u_reg_address);
i_err |= IIC_Wait_Ack();

for( i = 0 ; i < len ; i ++ )
{
IIC_Send_Byte(p_buffer[i]);

i_err |= IIC_Wait_Ack();
}
IIC_Stop();

kfree(p_buffer);

if(i_err == 0)
return 0;

return 1;
}

ssize_t EEPROM_Read(struct file *p_file, char __user *p_buf, size_t len, loff_t *p_lof)
{
int i = 0;
printk("----EEPROM read device-----n");


unsigned char u_temp;
unsigned char u_wait_err = 0;

unsigned char *p_buffer;
p_buffer = kzalloc(sizeof(char) * len, GFP_KERNEL);

if(len <= 0)
return 0;

IIC_Start();
IIC_Send_Byte(g_t_iic_struct.u_device_address << 1);
u_wait_err |= IIC_Wait_Ack();

IIC_Send_Byte(g_t_iic_struct.u_reg_address);
u_wait_err |= IIC_Wait_Ack();

IIC_Start();
IIC_Send_Byte((g_t_iic_struct.u_device_address << 1)+1);
u_wait_err |= IIC_Wait_Ack();

for(i = 0 ; i < len - 1 ; i ++)
{
//p_buffer[i] = IIC_Read_Byte( );
*p_buffer = IIC_Read_Byte( );
IIC_Ack();
p_buffer ++;
}
//p_buffer[len-1] = IIC_Read_Byte( );
*p_buffer = IIC_Read_Byte( );

IIC_NAck();//不需要響應

IIC_Stop();

#if 0
printk("read data is 0x%0xn",u_temp);
printk("error status:%dn",u_wait_err);
#endif

copy_to_user(p_buf,p_buffer - len + 1,len);

#if 0
printk("kernel array : n");
for(i = 0 ; i < len ; i ++)
printk("0x%0x n",p_buf[i]);
printk("n");
#endif

kfree(p_buffer);

if(u_wait_err == 0)
return 0;
return 1;
}


int EEPROM_Open(struct inode *p_inode, struct file *p_file)
{
printk("----EEPROM open device-----n");

//本句是將GPIO初始化。
IIC_Init();

return 0;
}


/*
*
* 規(guī)定:
* 在IOCTL中接收應用層傳過來的基本控制命令，包括i2c設備的地址，寄存器地址等。
* 在write,read函數(shù)中，才可以寫入buffer.
*
*/
long EEPROM_Ioctl (struct file *p_file, unsigned int cmd, unsigned long args)
{
switch(cmd)
{
case EEPROM_WRITE:
printk("----ioctl write---n");

copy_from_user(&g_t_iic_struct,(T_IIC_Struct *)args,4);

printk("u_device_address=0x%0xn",g_t_iic_struct.u_device_address);
printk("u_reg_address=0x%0xn",g_t_iic_struct.u_reg_address);

break;
case EEPROM_READ:
printk("----ioctl read---n");

copy_to_user((T_IIC_Struct *)args,&g_t_iic_struct,4);
printk("u_device_address=0x%0xn",g_t_iic_struct.u_device_address);
printk("u_reg_address=0x%0xn",g_t_iic_struct.u_reg_address);

break;
}
return 0;
}


static const struct file_operations EEPROM_File_Ops = {
.owner = THIS_MODULE,
.open = EEPROM_Open,
.read = EEPROM_Read,
.write = EEPROM_Write,
.unlocked_ioctl = EEPROM_Ioctl,

};

static int __init EEPROM_init(void)
{
int ret;
printk("-----EEPROM Init---------n");

g_major = register_chrdev(0,"EEPROM_Chrdev",&EEPROM_File_Ops);
g_p_class = class_create(THIS_MODULE, "EEPROM");
g_p_device = device_create(g_p_class, NULL,MKDEV(g_major, 0), NULL,
"i2c-%d", 1);

GPECON = ioremap(0x56000040,4);
GPEDAT = ioremap(0x56000044,4);

return ret;
}



static void __exit EEPROM_exit(void)
{
printk("-----EEPROM Exit---------n");

iounmap(GPECON);
iounmap(GPEDAT);

device_destroy(g_p_class,MKDEV(g_major, 0));
class_destroy(g_p_class);
unregister_chrdev(g_major,"EEPROM_Chrdev");

}

module_init(EEPROM_init);
module_exit(EEPROM_exit);



MODULE_AUTHOR("wit_yuan");
MODULE_DESCRIPTION("I2C-EEPROM by wit_yuan 2016-09-17 at beijing");
MODULE_LICENSE("GPL");

/*************end of file for EEPROM driver*****************************/

2.EEPROM.h文件:

#ifndef _EEPROM_H_
#define _EEPROM_H_







#endif

第二部分是Makefile文件內容:

obj-m:=EEPROM.o

KERNEL_DIR:= /home/wityuan/Downloads/linux-3.12.57

PWD:=$(shell pwd)

all:
make -C $(KERNEL_DIR) SUBDIRS=$(PWD) modules

clean:
rm *.o *.ko *.mod.clean

第三部分是應用層的測試程序EEPROM_App.c文件:

#include
#include
#include
#include
#include
#include


#define EEPROM_MAGIC m
#define EEPROM_WRITE _IOW(EEPROM_MAGIC,0,int)
#define EEPROM_READ _IOR(EEPROM_MAGIC,1,int)

typedef struct IIC_Struct{
unsigned char u_device_address;
unsigned char u_reg_address;

}T_IIC_Struct;

static T_IIC_Struct g_t_iic_struct;




int main(int argc,char *argv[])
{
int i_fd;
int i = 0;
unsigned char u_array_buf[10];

unsigned char u_array_write_buffer[10];

i_fd = open("/dev/i2c-1",O_RDWR);

if(i_fd < 0)
{
printf("open device errorn");
return -1;
}

printf("----open device ok----n");

g_t_iic_struct.u_device_address = 0x50;
g_t_iic_struct.u_reg_address = 0x0;

//初始化寫數(shù)據的數(shù)組
for(i = 0 ; i < 10 ; i ++)
u_array_write_buffer[i] = i + 1;


ioctl(i_fd,EEPROM_WRITE,&g_t_iic_struct);

//寫數(shù)據內容
write(i_fd,u_array_write_buffer,10);

//讀取EEPROM的數(shù)據

read(i_fd,u_array_buf,10);


printf("nread :n");
for(i = 0; i < 10 ; i ++)
printf("0x%0x ",u_array_buf[i]);

printf("n");

while(1);

return 0;
}

代碼結束了，具體的iic協(xié)議解釋性內容，還是一樣，參考stm32的模擬iic操作EEPROM吧。

這次，貼出一個實現(xiàn)效果圖:

好了，這就是本節(jié)的內容了。