2019独角兽企业重金招聘Python工程师标准>>> 
1 在内核中配置I2C 驱动
Linux-2.6.32.2 对S2C2440 的I2C 接口提供了完善的驱动，因此我们只需在内核中配置一下即可使用。
在内核源代码目录执行：make menuconfig，进入内核配置主菜单，依次选择进入如下子菜单：
Device Drivers --->
<*> I2C support --->
I2C Hardware Bus support --->
如图，我们看到这里已经选择好了“<*> S3C2410 I2C Driver”，这里的S3C2410 也可以适用于S3C2440，因为它们的I2C 端口及寄存器定义都是完全相同的。
以上配置所对应的驱动源代码为：linux-2.6.32.2/drivers/i2c/busses/i2c-s3c2410.c
2 、I2C-EEPROM测试源码
gedit eeprog.c#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "24cXX.h"
#define usage_if(a) do { do_usage_if( a , __LINE__); } while(0);
void do_usage_if(int b, int line)
{
const static char *eeprog_usage =
"I2C-24C08(256 bytes) Read/Write Program, ONLY FOR TEST!\n";
if(!b)
return;
fprintf(stderr, "%s\n[line %d]\n", eeprog_usage, line);
exit(1);
}
#define die_if(a, msg) do { do_die_if( a , msg, __LINE__); } while(0);
void do_die_if(int b, char* msg, int line)
{
if(!b)
return;
fprintf(stderr, "Error at line %d: %s\n", line, msg);
fprintf(stderr, " sysmsg: %s\n", strerror(errno));
exit(1);
}
static int read_from_eeprom(struct eeprom *e, int addr, int size)
{
int ch, i;
for(i = 0; i < size; ++i, ++addr)
{
die_if((ch = eeprom_read_byte(e, addr)) < 0, "read error");
if( (i % 16) == 0 )
printf("\n %.4x| ", addr);
else if( (i % 8) == 0 )
printf(" ");
printf("%.2x ", ch);
fflush(stdout);
}
fprintf(stderr, "\n\n");
return 0;
}
static int write_to_eeprom(struct eeprom *e, int addr)
{
int i;
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 ", i);
fflush(stdout);
die_if(eeprom_write_byte(e, addr, i), "write error");
}
fprintf(stderr, "\n\n");
return 0;
}
int main(int argc, char** argv)
{
struct eeprom e;
int op;
op = 0;
usage_if(argc != 2 || argv[1][0] != '-' || argv[1][2] != '\0');
op = argv[1][1];
fprintf(stderr, "Open /dev/i2c/0 with 8bit mode\n");
die_if(eeprom_open("/dev/i2c/0", 0x50, EEPROM_TYPE_8BIT_ADDR, &e) < 0,
"unable to open eeprom device file "
"(check that the file exists and that it's readable)");
switch(op)
{
case 'r':
fprintf(stderr, " Reading 256 bytes from 0x0\n");
read_from_eeprom(&e, 0, 256);
break;
case 'w':
fprintf(stderr, " Writing 0x00-0xff into 24C08 \n");
write_to_eeprom(&e, 0);
break;
default:
usage_if(1);
exit(1);
}
eeprom_close(&e);
return 0;
} gedit 24cXX.h#ifndef _24CXX_H_
#define _24CXX_H_
#include
#include
#define EEPROM_TYPE_UNKNOWN 0
#define EEPROM_TYPE_8BIT_ADDR 1
#define EEPROM_TYPE_16BIT_ADDR 2
struct eeprom
{
char *dev; // device file i.e. /dev/i2c-N
int addr; // i2c address
int fd; // file descriptor
int type; // eeprom type
};
/*
* opens the eeprom device at [dev_fqn] (i.e. /dev/i2c-N) whose address is
* [addr] and set the eeprom_24c32 [e]
*/
int eeprom_open(char *dev_fqn, int addr, int type, struct eeprom*);
/*
* closees the eeprom device [e]
*/
int eeprom_close(struct eeprom *e);
/*
* read and returns the eeprom byte at memory address [mem_addr]
* Note: eeprom must have been selected by ioctl(fd,I2C_SLAVE,address)
*/
int eeprom_read_byte(struct eeprom* e, __u16 mem_addr);
/*
* read the current byte
* Note: eeprom must have been selected by ioctl(fd,I2C_SLAVE,address)
*/
int eeprom_read_current_byte(struct eeprom *e);
/*
* writes [data] at memory address [mem_addr]
* Note: eeprom must have been selected by ioctl(fd,I2C_SLAVE,address)
*/
int eeprom_write_byte(struct eeprom *e, __u16 mem_addr, __u8 data);
#endif gedit 24cXX.c/***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "24cXX.h"
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);
}
static inline __s32 i2c_smbus_write_quick(int file, __u8 value)
{
return i2c_smbus_access(file,value,0,I2C_SMBUS_QUICK,NULL);
}
static inline __s32 i2c_smbus_read_byte(int file)
{
union i2c_smbus_data data;
if (i2c_smbus_access(file,I2C_SMBUS_READ,0,I2C_SMBUS_BYTE,&data))
return -1;
else
return 0x0FF & data.byte;
}
static inline __s32 i2c_smbus_write_byte(int file, __u8 value)
{
return i2c_smbus_access(file,I2C_SMBUS_WRITE,value,
I2C_SMBUS_BYTE,NULL);
}
static inline __s32 i2c_smbus_read_byte_data(int file, __u8 command)
{
union i2c_smbus_data data;
if (i2c_smbus_access(file,I2C_SMBUS_READ,command,
I2C_SMBUS_BYTE_DATA,&data))
return -1;
else
return 0x0FF & data.byte;
}
static inline __s32 i2c_smbus_write_byte_data(int file, __u8 command,
__u8 value)
{
union i2c_smbus_data data;
data.byte = value;
return i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_BYTE_DATA, &data);
}
static inline __s32 i2c_smbus_read_word_data(int file, __u8 command)
{
union i2c_smbus_data data;
if (i2c_smbus_access(file,I2C_SMBUS_READ,command,
I2C_SMBUS_WORD_DATA,&data))
return -1;
else
return 0x0FFFF & data.word;
}
static inline __s32 i2c_smbus_write_word_data(int file, __u8 command,
__u16 value)
{
union i2c_smbus_data data;
data.word = value;
return i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_WORD_DATA, &data);
}
static inline __s32 i2c_smbus_process_call(int file, __u8 command, __u16 value)
{
union i2c_smbus_data data;
data.word = value;
if (i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_PROC_CALL,&data))
return -1;
else
return 0x0FFFF & data.word;
}
/* Returns the number of read bytes */
static inline __s32 i2c_smbus_read_block_data(int file, __u8 command,
__u8 *values)
{
union i2c_smbus_data data;
int i;
if (i2c_smbus_access(file,I2C_SMBUS_READ,command,
I2C_SMBUS_BLOCK_DATA,&data))
return -1;
else {
for (i = 1; i <= data.block[0]; i++)
values[i-1] = data.block[i];
return data.block[0];
}
}
static inline __s32 i2c_smbus_write_block_data(int file, __u8 command,
__u8 length, __u8 *values)
{
union i2c_smbus_data data;
int i;
if (length > 32)
length = 32;
for (i = 1; i <= length; i++)
data.block[i] = values[i-1];
data.block[0] = length;
return i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_BLOCK_DATA, &data);
}
/* Returns the number of read bytes */
static inline __s32 i2c_smbus_read_i2c_block_data(int file, __u8 command,
__u8 *values)
{
union i2c_smbus_data data;
int i;
if (i2c_smbus_access(file,I2C_SMBUS_READ,command,
I2C_SMBUS_I2C_BLOCK_DATA,&data))
return -1;
else {
for (i = 1; i <= data.block[0]; i++)
values[i-1] = data.block[i];
return data.block[0];
}
}
static inline __s32 i2c_smbus_write_i2c_block_data(int file, __u8 command,
__u8 length, __u8 *values)
{
union i2c_smbus_data data;
int i;
if (length > 32)
length = 32;
for (i = 1; i <= length; i++)
data.block[i] = values[i-1];
data.block[0] = length;
return i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_I2C_BLOCK_DATA, &data);
}
/* Returns the number of read bytes */
static inline __s32 i2c_smbus_block_process_call(int file, __u8 command,
__u8 length, __u8 *values)
{
union i2c_smbus_data data;
int i;
if (length > 32)
length = 32;
for (i = 1; i <= length; i++)
data.block[i] = values[i-1];
data.block[0] = length;
if (i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
I2C_SMBUS_BLOCK_PROC_CALL,&data))
return -1;
else {
for (i = 1; i <= data.block[0]; i++)
values[i-1] = data.block[i];
return data.block[0];
}
}
static int i2c_write_1b(struct eeprom *e, __u8 buf)
{
int r;
// we must simulate a plain I2C byte write with SMBus functions
r = i2c_smbus_write_byte(e->fd, buf);
if(r < 0)
fprintf(stderr, "Error i2c_write_1b: %s\n", strerror(errno));
usleep(10);
return r;
}
static int i2c_write_2b(struct eeprom *e, __u8 buf[2])
{
int r;
// we must simulate a plain I2C byte write with SMBus functions
r = i2c_smbus_write_byte_data(e->fd, buf[0], buf[1]);
if(r < 0)
fprintf(stderr, "Error i2c_write_2b: %s\n", strerror(errno));
usleep(10);
return r;
}
static int i2c_write_3b(struct eeprom *e, __u8 buf[3])
{
int r;
// we must simulate a plain I2C byte write with SMBus functions
// the __u16 data field will be byte swapped by the SMBus protocol
r = i2c_smbus_write_word_data(e->fd, buf[0], buf[2] << 8 | buf[1]);
if(r < 0)
fprintf(stderr, "Error i2c_write_3b: %s\n", strerror(errno));
usleep(10);
return r;
}
#define CHECK_I2C_FUNC( var, label ) \
do { if(0 == (var & label)) { \
fprintf(stderr, "\nError: " \
#label " function is required. Program halted.\n\n"); \
exit(1); } \
} while(0);
int eeprom_open(char *dev_fqn, int addr, int type, struct eeprom* e)
{
int funcs, fd, r;
e->fd = e->addr = 0;
e->dev = 0;
fd = open(dev_fqn, O_RDWR);
if(fd <= 0)
{
fprintf(stderr, "Error eeprom_open: %s\n", strerror(errno));
return -1;
}
// get funcs list
if((r = ioctl(fd, I2C_FUNCS, &funcs) < 0))
{
fprintf(stderr, "Error eeprom_open: %s\n", strerror(errno));
return -1;
}
// check for req funcs
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_BYTE );
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_BYTE );
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_BYTE_DATA );
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_BYTE_DATA );
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_READ_WORD_DATA );
CHECK_I2C_FUNC( funcs, I2C_FUNC_SMBUS_WRITE_WORD_DATA );
// set working device
if( ( r = ioctl(fd, I2C_SLAVE, addr)) < 0)
{
fprintf(stderr, "Error eeprom_open: %s\n", strerror(errno));
return -1;
}
e->fd = fd;
e->addr = addr;
e->dev = dev_fqn;
e->type = type;
return 0;
}
int eeprom_close(struct eeprom *e)
{
close(e->fd);
e->fd = -1;
e->dev = 0;
e->type = EEPROM_TYPE_UNKNOWN;
return 0;
}
#if 0
int eeprom_24c32_write_byte(struct eeprom *e, __u16 mem_addr, __u8 data)
{
__u8 buf[3] = { (mem_addr >> 8) & 0x00ff, mem_addr & 0x00ff, data };
return i2c_write_3b(e, buf);
}
int eeprom_24c32_read_current_byte(struct eeprom* e)
{
ioctl(e->fd, BLKFLSBUF); // clear kernel read buffer
return i2c_smbus_read_byte(e->fd);
}
int eeprom_24c32_read_byte(struct eeprom* e, __u16 mem_addr)
{
int r;
ioctl(e->fd, BLKFLSBUF); // clear kernel read buffer
__u8 buf[2] = { (mem_addr >> 8) & 0x0ff, mem_addr & 0x0ff };
r = i2c_write_2b(e, buf);
if (r < 0)
return r;
r = i2c_smbus_read_byte(e->fd);
return r;
}
#endif
int eeprom_read_current_byte(struct eeprom* e)
{
ioctl(e->fd, BLKFLSBUF); // clear kernel read buffer
return i2c_smbus_read_byte(e->fd);
}
int eeprom_read_byte(struct eeprom* e, __u16 mem_addr)
{
int r;
ioctl(e->fd, BLKFLSBUF); // clear kernel read buffer
if(e->type == EEPROM_TYPE_8BIT_ADDR)
{
__u8 buf = mem_addr & 0x0ff;
r = i2c_write_1b(e, buf);
} else if(e->type == EEPROM_TYPE_16BIT_ADDR) {
__u8 buf[2] = { (mem_addr >> 8) & 0x0ff, mem_addr & 0x0ff };
r = i2c_write_2b(e, buf);
} else {
fprintf(stderr, "ERR: unknown eeprom type\n");
return -1;
}
if (r < 0)
return r;
r = i2c_smbus_read_byte(e->fd);
return r;
}
int eeprom_write_byte(struct eeprom *e, __u16 mem_addr, __u8 data)
{
if(e->type == EEPROM_TYPE_8BIT_ADDR) {
__u8 buf[2] = { mem_addr & 0x00ff, data };
return i2c_write_2b(e, buf);
} else if(e->type == EEPROM_TYPE_16BIT_ADDR) {
__u8 buf[3] =
{ (mem_addr >> 8) & 0x00ff, mem_addr & 0x00ff, data };
return i2c_write_3b(e, buf);
}
fprintf(stderr, "ERR: unknown eeprom type\n");
return -1;
} gedit MakefileCFLAGS= -Wall -O2
CC=arm-linux-gcc
i2c: eeprog.o 24cXX.o
$(CC) $(CFLAGS) -o i2c eeprog.o 24cXX.o
clean:
rm -f i2c 24cXX.o eeprog.o3、编译部署
# make生成可执行文件 i2c，上传到开发板
4、查看设备号
[root@MrBenjamin]# cat /proc/devices | grep i2c
89 i2c89 为i2c设备号
5、生成设备文件（如果设备文件已存在，跳过此步）
cd /dev
mkdir i2c
mknod -m 666 /dev/i2c/0 c 89 06、测试，看截图
读测试
写测试
