I2C在U-Boot中的使用

u-boot提供了I2C的接口，驱动程序在 ./cpu/arm920t/s3c24x0/i2c.c 中，在 smdk2440.h 中加入

 

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

 

#define CFG_I2C_SPEED        100000    /* I2C speed and slave address */
#define CFG_I2C_SLAVE        0x50

#define CFG_I2C_EEPROM_ADDR_LEN     1    /* Bytes of address        */
/* mask of address bits that overflow into the "EEPROM chip address"    */
#define CFG_I2C_EEPROM_ADDR_OVERFLOW    0x07

 

在board.c 文件中加入 write_info2eeprom() 将u－boot 生成的日期写入 24c16的 0x50位置中。

 

static void write_info2eeprom()
{
    memset(uboot_info,0,sizeof(uboot_info);
    strcpy(uboot_info, __DATE__);
    i2c_init(CFG_I2C_SPEED, CFG_I2C_SLAVE);
    i2c_write(CFG_I2C_SLAVE, 0x50, 1, uboot_info, 6);
    memset(uboot_info,0,sizeof(uboot_info);
    i2c_read(CFG_I2C_SLAVE, 0x50, 1, uboot_info, 6);
    printf("read back: %s\n", uboot_info);
}

 

其中读/写这2个函数的说明

/*
 * Read/Write interface:
 *   chip:    I2C chip address, range 0..127
 *   addr:    Memory (register) address within the chip
 *   alen:    Number of bytes to use for addr (typically 1, 2 for larger
 *              memories, 0 for register type devices with only one
 *              register)
 *   buffer:  Where to read/write the data
 *   len:     How many bytes to read/write
 *
 *   Returns: 0 on success, not 0 on failure
 */
int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len);
int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len);

其中alen 为1,说明chip是8bit的， 为2则是 16bit的。