arm7tdmi的i2c驱动注释

//这个i2c接口只支持主模式 The Master I2C Interface Module supports I2C Master Only mode with

/*

1. 7 bits address DEVICE 7位设备地址

2. 8 bits sub address 8位设备寄存器地址

3. Master write to slave receiver in single or multiple mode (data loop) 写入多个从设备

16 bytes deep transmit FIFO

4. Master simple Read to slave receiver 读入数据

5. Read Combined cycle

6. 3-bit programmable pre-scale internal clock divider and 7-bit programmable SCL clock divider to 

support wide clock frequency range of module input clock signal. The I2C SCL clock

frequency are: I2C Standard Mode: 100 kHz

I2C Fast Mode: 400 kHz

两个时钟模式，100KHZ与400KHZ

7. 3-bit programmable spike filter to provide I2C bus input signal noise filtering ability.

8. Asynchronous Rhea bus access with Zero Wait State Insertion

Except for the synchronization of Rhea read access to STATUS_ACTIVITY.

9. Error Handling Capability during I2C bus access

*/

#include <stdint.h>

#include <stdio.h>

#include <debug.h>

#include <memory.h>

#include <i2c.h>

#define BASE_ADDR_I2C 0xfffe2800
//i2c内存地址

#define I2C_REG(x) (BASE_ADDR_I2C+(x))
//注册函数？

enum i2c_reg { //枚举注册值I2C register mapping
DEVICE_REG
= 0,//DEVICE_REG FFFE:2800 7 bits R/W 1000 0000 
ADDRESS_REG,//ADDRESS_REG FFFE:2801 8 bits R/W 0000 0000  
DATA_WR_REG,//DATA_WR_REG FFFE:2802 8 bits R/W 0000 0000
fifo数据注册
DATA_RD_REG,//DATA_RD_REG FFFE:2803 8 bits R 0000 0000
CMD_REG,//CMD_REG FFFE:2804 6 bits R/W 1101 0001
CONF_FIFO_REG,//CONF_FIFO_REG FFFE:2805 4 bits R/W 1111 1111
fifo数据的长度注册
CONF_CLK_REG,//CONF_CLK_REG FFFE:2806 6 bits R/W 1100 0000
CONF_CLK_FUNC_REF,//CONF_CLK_FUNC_REF FFFE:2807 7 bits R/W 1000 1010
STATUS_FIFO_REG,//STATUS_FIFO_REG FFFE:2808 6 bits R 1100 0010
STATUS_ACTIVITY_REG,//STATUS_ACTIVITY_REG FFFE:2809 4 bits R 1111 0000
i2c激活状态

};

#define I2C_CMD_SOFT_RESET (1 << 0)//软件复位

#define I2C_CMD_EN_CLK (1 << 1)//时钟使能

#define I2C_CMD_START (1 << 2)//开始命令

#define I2C_CMD_RW_READ (1 << 3)//读写控制

#define I2C_CMD_COMP_READ (1 << 4)//comp控制

#define I2C_CMD_IRQ_ENABLE (1 << 5)//中断打开

#define I2C_STATUS_ERROR_DATA (1 << 0)//数据状态错误

#define I2C_STATUS_ERROR_DEV (1 << 1)//驱动状态错

#define I2C_STATUS_IDLE (1 << 2) // idle状态值1: not idle, 0: idle i2c是否处于忙的状态

#define I2C_STATUS_INTERRUPT (1 << 3)//

#define FIFO_SIZE // 填充fifo达到fifo_full状态

#define STATUS_FIFO_REG_FIFO_FULL
1//1表示满，0表示不满

#define STATUS_FIFO_REG_FIFO_EMPTY (1<<2) //0表示非空，1表示空。

#define STATUS_FIFO_REG_READ_CPT  (15<<3)//fifo位0-15，状态标志

/*int i2c_write(u_int8_t chip, //芯片的i2c地址，不包含读写位

u_int32_t addr, //芯片内的读写地址，比如寄存器地址

int alen, //这个要看代码才知道是地址的长度。比如有的flash比较大就有16位地址。

              //uboot支持32位地址，不过要看驱动支不支持。0=8bit,1=16bit,2=32bit地址长度

u_int8_t *buf, //数据

int len)            //数据长度

*/

{
uint8_t cmd;

/* 如果不是8位数据
Calypso I2C controller doesn't support fancy addressing */
if (alen > 1)
return -1;

/*数据长度大于16位也返回错误 FIXME: implement writes longer than fifo size */
if (len > 16)
return -1;
//打印从设备地址寄存器
printd("i2c_write(chip=0x%02u, addr=0x%02u): ", chip, addr);
//注册设备地址值
writeb(chip & 0x7f, I2C_REG(DEVICE_REG));
writeb(addr & 0xff, I2C_REG(ADDRESS_REG));

/*写入数据长度注册 we have to tell the controller how many bits we'll put into the fifo ?!? */
writeb(len-1, I2C_REG(CONF_FIFO_REG));

/* fifo数据注册写入从设备fifo数据
fill the FIFO */
while (len--) {
uint8_t byte = *buffer++;
writeb(byte, I2C_REG(DATA_WR_REG));
printd("%02X ", byte);
}
dputchar('\n');

/*这里是最关键的部分命令写入部分*/

/*开始写入 start the transfer */
cmd = readb(I2C_REG(CMD_REG));
//读取注册命令枚举
cmd |= I2C_CMD_START;
//开始i2c
writeb(cmd, I2C_REG(CMD_REG));//写入注册命令

/* 判断是否传输完成ackwait until transfer completes */
while (1) {
uint8_t reg = readb(I2C_REG(STATUS_ACTIVITY_REG));//读取i2c激活状态
printd("I2C Status: 0x%02x\n", reg & 0xf);
if (!(reg & I2C_STATUS_IDLE)) // 0: idle 1: not idle如果状态是空闲返回，忙继续循环while
break;
}
dputs("I2C transfer completed\n");
//传输完成函数结束
return 0;

}

int i2c_read(uint8_t chip, uint32_t addr, int alen, const uint8_t *buffer, int len)

{
uint8_t cmd0;

/* Calypso I2C controller doesn't support fancy addressing */
if (alen > 1)
return -1;

/* FIXME: implement writes longer than fifo size */
if (len > 16)
return -1;

printd("i2c_write(chip=0x%02u, addr=0x%02u): ", chip, addr);

writeb(chip & 0x7f, I2C_REG(DEVICE_REG));
writeb(addr & 0xff, I2C_REG(ADDRESS_REG));

/* start the transfer */
cmd0 = readb(I2C_REG(CMD_REG));
cmd0 |= I2C_CMD_RW_READ;
cmd0 |= I2C_CMD_START;
writeb(cmd, I2C_REG(CMD_REG));

// if(~(STATUS_FIFO_REG_FIFO_EMPTY&I2C_REG(STATUS_FIFO_REG))){
//读取fifo长度

// len =readb(I2C_REG(CONF_FIFO_REG));

// readb(len+1, I2C_REG(CONF_FIFO_REG));
/* fill the FIFO */

*buffer=readb(I2C_REG(DATA_RD_REG));
printd("%02X ", byte);
dputchar('\n');

// }
/* wait until transfer completes */
while (1) {
uint8_t reg = readb(I2C_REG(STATUS_ACTIVITY_REG));
printd("I2C Status: 0x%02x\n", reg & 0xf);
if (!(reg & I2C_STATUS_IDLE)) // 0: idle 1: not idle
break;
}
dputs("I2C transfer completed\n");
cmd0 |= ~I2C_CMD_RW_READ;
writeb(cmd, I2C_REG(CMD_REG));
return *buffer;

}

void i2c_init(int speed, int slaveadd)

{
/* scl_out = clk_func_ref / 3,
  clk_func_ref = master_clock_freq / (divisor_2 + 1)
  master_clock_freq = ext_clock_freq / divisor_1 */
/* clk_func_ref = scl_out * 3,
  divisor_2 = (master_clock_freq / clk_func_ref) - 1
  divisor_1 = ext_clock_freq / master_clock_freq */
/* for a target freq of 200kHz:
ext_clock_freq = 13MHz
clk_func_ref = 3 * 300kHZ = 600kHz
divisor_1 = 1 => master_clock_freq = ext_clock_freq = 13MHz
divisor_2 = 21 => clk_func_ref = 13MHz / (21+2) = 590.91 kHz
scl_out = clk_func_ref / 3 = 509.91 kHz / 3 = 196.97kHz

这个是时钟设置，根据datesheet这里没法修改 */

writeb(I2C_CMD_SOFT_RESET, I2C_REG(CMD_REG));

writeb(0x00, I2C_REG(CONF_CLK_REG));
writeb(21, I2C_REG(CONF_CLK_FUNC_REF));

writeb(I2C_CMD_EN_CLK, I2C_REG(CMD_REG));

}