Embedded driver transplantation IIC bus driver transplantation

Migration environment

Host development environment: Ubuntu 12.04

BootLoader：u-boot-1.1.6

kernel：linux-2.6.30.4

CPU：s3c2440

Development board: TQ2440

Transplantation steps

The IIC bus driver already exists in the 2.6.30.4 kernel. You only need to configure it and compile the kernel image to use the IIC bus. There is an IIC bus EEPROM (AT24C02) in TQ2440. You can test whether the IIC bus is driven by reading and writing it.

1. Configure the kernel

Device Drivers --->

    <* > I2C support --->

       --- I2C support

   <* > I2C device interface

   I2C Hardware Bus support --->

   *** I2C system bus drivers (mostly embedded / system-on-chip)

        <* > S3C2410 I2C Driver

2. Writing of IIC test program

You only need to complete the operation on the i2c_smbus_ioctl_bus structure, which is defined in the "include/linux/i2c-dev.h" file of the kernel source code.

Write 256 numbers into AT24C02 and then read them out. The written numbers start from 0xFF and end at 0x00.

The source code is as follows:

/*************************************

NAME:i2c_rw.c

*************************************/

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define CHIP_ADDR 0x50 //Device address

#define I2C_DEV "/dev/i2c-0"

struct eeprom

{

char *dev; // device name, i2c-0

int addr; // device address

int fd; // device handle

};

static inline __s32 i2c_smbus_access(int file, char read_write, __u8 command, int size, union i2c_smbus_data *data)

{

struct i2c_smbus_ioctl_data args;

args.read_write = read_write;

args.command = command;

args.size = size;

args.data = data;

return ioctl(file, I2C_SMBUS, &args);

}

int eeprom_read_byte(struct eeprom* e, __u16 mem_addr)

{

int r;

union i2c_smbus_data data;

ioctl(e->fd, BLKFLSBUF);

__u8 buf = mem_addr & 0x0ff;

r = i2c_smbus_access(e->fd, I2C_SMBUS_WRITE, buf, I2C_SMBUS_BYTE, NULL);;

if (r < 0)

  return r;

if (i2c_smbus_access(e->fd, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data))

  return -1;

else

  return 0x0FF & data.byte;

}

int eeprom_write_byte(struct eeprom *e, __u16 mem_addr, __u8 data)

{

int r;

__u8 command = mem_addr & 0x00ff;

union i2c_smbus_data i2cdata;

i2cdata.byte = data;

r = i2c_smbus_access(e->fd, I2C_SMBUS_WRITE, command, I2C_SMBUS_BYTE_DATA, &i2cdata);

if(r < 0)

  printf("iic write error");

usleep(10);

  return r;

}

int eeprom_open(char *dev_name, int addr, struct eeprom *e)

{

int funcs, fd, r;

e->fd = e->addr = 0;

e->dev = 0;

fd = open(dev_name, O_RDWR);

if(fd <= 0)

{

printf("iic open errorn");

return -1;

}

// set working device

ioctl(fd, I2C_TENBIT, 0);

ioctl(fd, I2C_SLAVE, addr);

e->fd = fd;

e->addr = addr;

e->dev = dev_name;

return 0;

}

int eeprom_close(struct eeprom *e)

{

close(e->fd);

e->fd = -1;

e->dev = 0;

return 0;

}

static int read_from_eeprom(struct eeprom *e, int addr, int size)

{

int temp, i, ret;

for(i = 0; i < size; ++i, ++addr)

{

temp = eeprom_read_byte(e, addr);

if(temp < 0)

{

printf("iic read error !");

}

if( (i % 16) == 0 )

printf("n %.4x| ", addr);

else if( (i % 8) == 0 )

printf(" ");

printf("%.2x ", temp);

fflush(stdout);

}

printf("nn");

return 0;

}

static int write_to_eeprom(struct eeprom *e, int addr)

{

int i, ret;

for(i=0, addr=0; i<256; i++, addr++)

{

if( (i % 16) == 0 )

  printf("n %.4x| ", addr);

else if( (i % 8) == 0 )

  printf(" ");

  printf("%.2x ", 255-i);

  fflush(stdout);

ret = eeprom_write_byte(e, addr, 255-i);

if(ret < 0)

{

     printf("iic write error !");

}

}

fprintf(stderr, "nn");

return 0;

}

int main (void)

{

struct eeprom e;

int ret;

ret = eeprom_open(I2C_DEV, CHIP_ADDR, &e);

if(ret < 0)

{

printf("i2c device (AT24C02) open failed !n");

return (-1);

}

printf(" Writing 0x00-0xff into AT24C02 n");

write_to_eeprom(&e, 0);

printf(" Reading 256 bytes from 0x0n");

read_from_eeprom(&e, 0, 256);

eeprom_close(&e);

return(0);

}

The Makefile is as follows:

CROSS=arm-linux-

all: i2c_rw

i2c_rw:i2c_rw.c

$(CROSS)gcc -o i2c_rw i2c_rw.c

$(CROSS)strip i2c_rw

clean:

@rm -vf i2c_rw *.o *~

3. IIC test

After compiling the program "i2c_rw", put it in the "/sbin/" directory of the NFS file system, and then run it. The screenshot is as follows: