I2C
1 功能概述
I2C 接口可以通过数据引脚 (SDA) 和时钟引脚 (SCL) 连接到 I2C或 SMBus总线。SDA 线和 SCL 线均设置为漏极开漏 (open-drain) 输出，并接上拉电阻 (pull-up resistor)。因此，I2C 和 SMBus 总线上可以挂载多个器件。I2C 接口的每次传输都是由主器件 (Master) 发起和控制，
本章主要介绍通过I2C接口完成对EEPROM芯片的数据读写。目前，cp侧不允许使用I2C，ap侧支持使用I2C0和I2C1。
I2C相关的理论介绍参考: I2C的驱动
备注
1.cp侧不允许使用I2C0和I2C1；
2.ap侧支持使用I2C0和I2C1;
2 代码路径
- demo路径：
components\bk_cli\cli_i2c.c
- 驱动源码路径：
ap\middleware\driver\i2c\i2c_unified.c(统一API层，自动路由到硬件或模拟I2C)ap\middleware\driver\i2c\i2c_driver.c(硬件I2C驱动实现)ap\middleware\driver\i2c\sim_i2c_driver.c(软件模拟I2C驱动实现)I2C相关的api介绍参考: I2C的api介绍
备注
1.i2c_unified.c: 统一API层，根据I2C ID自动路由到硬件或模拟I2C实现
2.i2c_driver.c: 硬件I2C驱动实现，使用硬件中断方式
3.sim_i2c_driver.c: 软件模拟I2C驱动实现，通过GPIO模拟I2C时序
3 cli命令简介
demo运行依赖的宏配置：
NAME
Description
File
value
CONFIG_I2C
support i2c
ap\middleware\soc\bk7258\bk7258.defconfigy
CONFIG_I2C_SUPPORT_ID_BITS
support i2c0 or i2c1
ap\middleware\soc\bk7258\bk7258.defconfig1
CONFIG_SIM_I2C
value y:support software； n: hardware i2c
ap\middleware\soc\bk7258\bk7258.defconfign
CONFIG_SIM_I2C_HW_BOARD_V3
support Touch Screen with i2c
ap\middleware\soc\bk7258\bk7258.defconfigy
demo支持的命令如下表：
Command
Param
Description
i2c_driver init
none
init I2C driver control memory
i2c_driver deinit
none
free all resource related to I2C
i2c {id} init
i2c id number
power up and start the I2C id
i2c {id} deinit
i2c id number
power down and Stop the I2C id
i2c {id} memory_write {data_size} {dev_addr} {mem_addr_size}
id: i2c id number
write data_size bytes of data to the slave device with address dev_id
data_size:size of data written
dev_addr: slave device address
mem_addr_size: size of memory_addr
i2c {id} memory_read {data_size} {dev_addr} {mem_addr_size}
id: i2c id
read data_size bytes of data from slave device
data_size:size of data read
dev_addr: slave device address
mem_addr_size: size of memory_addr
4 I2C PIN脚描述
I2C0对应有1组PIN脚，对应的硬件管脚如下：
I2C0功能
组0
I2C0_CLK
GPIO0
I2C0_SDA
GPIO1
- I2C1对应有1组PIN脚，对应的硬件管脚如下：
I2C1功能
组0
I2C1_CLK
GPIO20
I2C1_SDA
GPIO21
4 演示介绍
demo1执行的步骤如下：
1、准备好EEPROM的模块，型号为ZD24C128A，使用I2C1连接方式如下：
Figure 1. i2c_connect图
2、顺序发送以下命令
cpu1 i2c 1 init
[11:45:42.140]发→◇cpu1 i2c 1 init [11:45:42.145]收←◆cpu1 i2c 1 init os:I(6720):create shell_handle, tcb=28078db0, stack=[28077188-28078d88:7168], prio=5 $ $cpu1:i2c:I(6178):I2C(1) init ok, baud_rate:400000 cpu1:cli:I(6178):i2c(1) initcpu1 i2c 1 memory_write 8 50 1//向EEPROM中写入8字节数据
[11:45:43.027]发→◇cpu1 i2c 1 memory_write 8 50 1 [11:45:43.034]收←◆cpu1 i2c 1 memory_write 8 50 1 os:I(7608):create shell_handle, tcb=28078db0, stack=[28077188-28078d88:7168], prio=5 $ $cpu1:cli:I(7066):i2c(1) memory_write buf_len:8
- cpu1 i2c 1 memory_read 8 50 1 //从EEPROM中读取8字节数据
3、时序图
写时序图
Figure 2. i2c_wr_Sequence_ZD24C128A
读时序图
Figure 3. i2c_rd_Sequence_ZD24C128A
demo2执行的步骤如下：
1、准备好EEPROM的模块，型号为FM24C04B，使用I2C1连接方式如下：
Figure 4. i2c_connect图
2、顺序发送以下命令
cpu1 i2c 1 init
[16:44:55.619]发→◇cpu1 i2c 1 init [16:44:55.622]收←◆cpu1 i2c 1 init os:I(3120):create shell_handle, tcb=28078db0, stack=[28077188-28078d88:7168], prio=5 $ $cpu1:i2c:I(2984):I2C(1) init ok, baud_rate:400000 cpu1:cli:I(2984):i2c(1) initcpu1 i2c 1 memory_write 8 50 0//向EEPROM中写入8字节数据
[16:44:58.285]发→◇cpu1 i2c 1 memory_write 8 50 0 [16:44:58.292]收←◆cpu1 i2c 1 memory_write 8 50 0 os:I(5788):create shell_handle, tcb=28078db0, stack=[28077188-28078d88:7168], prio=5 $ $cpu1:cli:I(5652):i2c(1) memory_write buf_len:8
- cpu1 i2c 1 memory_read 8 50 0 //从EEPROM中读取8字节数据
3、时序图
写时序图
Figure 5. i2c_wr_Sequence_FM24C04B
读时序图
Figure 6. i2c_rd_Sequence_FM24C04B
备注
注意：memory_write命令中的dev_addr 50为16进制，因为i2c驱动中会将dev_addr左移一位，所以传入的dev_addr需要将ZD24C128A的dev_addr（1010b）右移一位。