測試基于linux-2.6.27的9G9260開發板I2C驅動

1，找到drivers/i2c/busses/i2c-at91.c文件

root@yuanxh-desktop:/home/yuanxh/sam9260/linux-2.6.27-9g9260# vi drivers/i2c/busses/Makefile

在第28行看到：

obj-$(CONFIG_I2C_AT91) += i2c-at91.o

2， 找到drivers/i2c/busses/Kconfig文件

root@yuanxh-desktop:/home/yuanxh/sam9260/linux-2.6.27-9g9260# vi drivers/i2c/busses/Kconfig

在第259行看到：

config I2C_AT91

tristate Atmel AT91 I2C Two-Wire interface (TWI)

depends on ARCH_AT91 EXPERIMENTAL BROKEN

help

This supports the use of the I2C interface on Atmel AT91

processors.

This driver is BROKEN because the controller which it uses

will easily trigger RX overrun and TX underrun errors. Using

low I2C clock rates may partially work around those issues

on some systems. Another serious problem is that there is no

documented way to issue repeated START conditions, as needed

to support combined I2C messages. Use the i2c-gpio driver

unless your system can cope with those limitations.

說明AT91 I2C標準驅動不穩定，需要用GPIO模擬!!!

3，編譯配置內核

root@yuanxh-desktop:/home/yuanxh/sam9260/linux-2.6.27-9g9260# make menuconfig

進入配置菜單添加驅動到內核：

Device Drivers --->

*> I2C support --->

*> I2C device interface

I2C Hardware Bus support --->

*> GPIO-based bitbanging I2C

4, 編譯內核生成驅動

root@yuanxh-desktop:/home/yuanxh/sam9260/linux-2.6.27-9g9260# make

5, 查看內核啟動信息

i2c /dev entries driver

i2c-gpio i2c-gpio: using pins 55 (SDA) and 56 (SCL)

6，查看內核系統信息

# cat /proc/devices

會看到

Character devices:

...

89 i2c

...

# cat /sys/devices/platform/i2c-gpio/i2c-adapter:i2c-0/name

i2c-gpio-1

7，建立設備結點

mknod /dev/i2c-0 c 89 0

8，編譯測試代碼

root@yuanxh-desktop:/home/yuanxh/sam9260/i2ctest-1.0-9g9260# arm-linux-gcc -o i2ctest i2ctest.c

root@yuanxh-desktop:/home/yuanxh/sam9260/i2ctest-1.0-9g9260# cp i2ctest /nfsboot/rootfs/app

9，運行測試代碼

# /app/i2ctest

I2C Test version 1.0-9g9260 (yuanxihua@21cn.com) Buile on Jan 5 2009 00:54:45

buf[0x00] = 0x46

...

附件：

//i2ctest.c

#include

#include

#include

#include

#include

#include

#define CHIP_ADDR 0x50 //24C64

#define PAGE_SIZE 32

#define I2C_DEV /dev/i2c-0

static int read_eeprom(int fd,char buff[],int addr,int count)

{

int res;

if (write(fd,addr,1)!=1)

{

printf(Can't write %s's addr %dn,I2C_DEV,addr);

return -1;

}

res = read(fd,buff,count);

printf(read %d bytes at 0x%02xnr,res,addr);

return res;

}

static int write_eeprom(int fd,char buff[],int addr,int count)

{

int res;

int i;

static char sendbuffer[PAGE_SIZE+1];

memcpy(sendbuffer+1,buff,count);

sendbuffer[0]=addr;

res = write(fd,addr,count+1);

printf(write %d bytes at 0x%02xnr,res,addr);

return res;

}

int main(void)

{

int fd,i,res;

unsigned char buf[PAGE_SIZE];

printf(I2C Test version 1.0-9g9260 (yuanxihua@21cn.com) Buile on %s %snr,__DATE__,__TIME__);

fd=open(I2C_DEV,O_RDWR);

if(fd0)

{

printf(Can't Open %s !!!nr,I2C_DEV);

return -1;

}

res = ioctl(fd,I2C_TENBIT,0);

res = ioctl(fd,I2C_SLAVE,CHIP_ADDR);

for(i=0;i

{

// write_eeprom(fd,buf,i,1);

}

for(i=0;i

{

read_eeprom (fd,buf+i,i,1);

printf(buf[0x%02x] = 0x%02xnr,i,buf[i]);

}

close(fd);

return 0;

}