移植環境

1，主機環境：VMare下CentOS 5.5 ，1G內存。

2，集成開發環境：Elipse IDE

3，編譯編譯環境：arm-linux-gcc v4.4.3，arm-none-eabi-gcc v4.5.1。

4，開發板：mini2440，2M nor flash，128M nand flash。

5，u-boot版本：u-boot-2009.08

6，參考文章：

10.1，實現u-boot的I2C EEPROM功能

mini2440開發板上的AT24C08A芯片提供了8kbyte的非易失的EEPROM存儲空間，而且是通過I2C協議進行讀寫的，U-boot提供了對I2C和EEPROM的操作支持。

打開/include/configs/mini2440.h，定位到206行附近，加入宏定義：
/*
 * SD Card support
 * */
#if 1
#define CONFIG_CMD_MMC
#define CONFIG_MMC  1
#define CONFIG_MMC_S3C 1 /* Enabling the MMC driver */
#define CFG_MMC_BASE  0xff000000
#endif

/**
 * I2C and EEPROM support
 */
#if 1
#define CONFIG_CMD_EEPROM
#define CONFIG_CMD_I2C

#define CONFIG_DRIVER_S3C24X0_I2C    1    /* we use the buildin I2C controller */
#define CONFIG_HARD_I2C    1        /* I2C with hardware support */

#define CONFIG_SYS_I2C_SPEED        100000    /* I2C speed and slave address */
#define CONFIG_SYS_I2C_SLAVE        0x7F

#define CONFIG_SYS_I2C_EEPROM_ADDR        0x50    /* EEPROM at24c08        */
#define CONFIG_SYS_I2C_EEPROM_ADDR_LEN     1    /* Bytes of address        */
/* mask of address bits that overflow into the 'EEPROM chip address'    */
#define CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW    0x07
#define CONFIG_SYS_EEPROM_PAGE_WRITE_BITS 4    /* The Catalyst CAT24WC08 has    */
                    /* 16 byte page write mode using*/
                    /* last 4 bits of the address    */
#define CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS    10   /* and takes up to 10 msec */
#define CONFIG_SYS_EEPROM_PAGE_WRITE_ENABLE

//#define CONFIG_ENV_IS_IN_EEPROM    1    /* use EEPROM for environment vars */
//#define CONFIG_ENV_OFFSET       0x000    /* environment starts at offset 0 */
//#define CONFIG_ENV_SIZE         0x400    /* 1KB  */

#endif

10.2，重新編譯測試

待編譯完成后，nor檔下載nand檔啟動，操作如下：

[u-boot@MINI2440]# help i2c
i2c - I2C sub-system

Usage:
i2c speed [speed] - show or set I2C bus speed
i2c md chip address[.0, .1, .2] [# of objects] - read from I2C device
i2c mm chip address[.0, .1, .2] - write to I2C device (auto-incrementing)
i2c mw chip address[.0, .1, .2] value [count] - write to I2C device (fill)
i2c nm chip address[.0, .1, .2] - write to I2C device (constant address)
i2c crc32 chip address[.0, .1, .2] count - compute CRC32 checksum
i2c probe - show devices on the I2C bus
i2c reset - re-init the I2C Controller
i2c loop chip address[.0, .1, .2] [# of objects] - looping read of device
[u-boot@MINI2440]# i2c speed
Current bus speed=100000
[u-boot@MINI2440]# i2c probe
Valid chip addresses: 50 51 52 53
[u-boot@MINI2440]# i2c

在上面的mini2440.h文件中， CONFIG_ENV_IS_IN_EEPROM 是注釋掉的，如果想將環境變量保存的位置設置在EEPROM中，需要將nand flash的CONFIG_ENV_IS_IN_NAND  的相關幾行代碼注釋掉，將上面注釋掉的幾行代碼恢復即可。這里先不作修改了。