IIC 简介
IIC (Inter－Integrated Circuit) 总线是一种由 NXP (原PHILIPS) 公司开发的两线式串行通信总线，多用于主控制器和从设备之间的主从式通信，且任意时刻只能有一个主机。
IIC 总线由数据线 SDA 和时钟线 SCL 构成，可实现在主控制器与被控设备之间、设备与设备之间双向通信，高速 IIC 总线一般可达 400kbps 以上。
为驱动实验室自研基于 DAC60502 的双通道电流输出模块，基于 ZYNQ 平台，将 PS 端的 GPIO 资源通过 EMIO 引出到 PL 端，使用 PL 端引脚资源连接 IIC 从设备，既使用 EMIO 模拟 IIC 实现主从通信控制。 
模拟 IIC 示例代码
- iic_io.c
/** * Copyright (c) 2022-2023，HelloAlpha * * Change Logs: * Date Author Notes */ #include "iic_io.h" extern XGpioPs GpioPs; void SCL_OUT(void) { XGpioPs_SetDirectionPin(&GpioPs, SCL_PIN, GPIO_MODEL_OUTPUT); XGpioPs_SetOutputEnablePin(&GpioPs, SCL_PIN, GPIO_OUTPUT_ENABLE); } void SCL_HIGH(void) { XGpioPs_WritePin(&GpioPs, SCL_PIN, GPIO_SET); } void SCL_LOW(void) { XGpioPs_WritePin(&GpioPs, SCL_PIN, GPIO_RESET); } void SDA_IN(void) { XGpioPs_SetDirectionPin(&GpioPs, SDA_PIN, GPIO_MODEL_INPUT); } uint32_t SDA_READ(void) { return XGpioPs_ReadPin(&GpioPs, SDA_PIN); } void SDA_OUT(void) { XGpioPs_SetDirectionPin(&GpioPs, SDA_PIN, GPIO_MODEL_OUTPUT); XGpioPs_SetOutputEnablePin(&GpioPs, SDA_PIN, GPIO_OUTPUT_ENABLE); } void SDA_HIGH(void) { XGpioPs_WritePin(&GpioPs, SDA_PIN, GPIO_SET); } void SDA_LOW(void) { XGpioPs_WritePin(&GpioPs, SDA_PIN, GPIO_RESET); } int IIC_Init(void) { SCL_OUT(); SCL_HIGH(); SDA_OUT(); SDA_HIGH(); return 0; }
- iic_io.h
/** * Copyright (c) 2022-2023，HelloAlpha * * Change Logs: * Date Author Notes */ #ifndef __IIC_IO_H__ #define __IIC_IO_H__ #include "xgpiops.h" #define SCL_PIN 54 #define SDA_PIN 55 #define GPIO_MODEL_INPUT 0 #define GPIO_MODEL_OUTPUT 1 #define GPIO_OUTPUT_DISABLE 0 #define GPIO_OUTPUT_ENABLE 1 #define GPIO_RESET 0 #define GPIO_SET 1 void SCL_OUT(void); void SCL_HIGH(void); void SCL_LOW(void); void SDA_IN(void); uint32_t SDA_READ(void); void SDA_OUT(void); void SDA_HIGH(void); void SDA_LOW(void); int IIC_Init(void); #endif
- iic_ctrl.c
/** * Copyright (c) 2022-2023，HelloAlpha * * Change Logs: * Date Author Notes */ #include "iic_ctrl.h" #include "sleep.h" #define I2C_DELAY(...) usleep(__VA_ARGS__) void IIC_Start(void) { SDA_OUT(); SDA_HIGH(); SCL_HIGH(); I2C_DELAY(4); SDA_LOW(); I2C_DELAY(4); SCL_LOW(); I2C_DELAY(2); } void IIC_Stop(void) { SDA_OUT(); SCL_LOW(); SDA_LOW(); I2C_DELAY(4); SCL_HIGH(); SDA_HIGH(); I2C_DELAY(4); } // 1，接收应答失败 // 0，接收应答成功 uint8_t IIC_Wait_Ack(void) { uint8_t ucErrTime=0; SDA_OUT(); SDA_HIGH(); I2C_DELAY(1); SCL_HIGH(); I2C_DELAY(1); SDA_IN(); while(SDA_READ()) { ucErrTime++; if(ucErrTime > 250) { IIC_Stop(); return 1; } } SCL_LOW(); return 0; } //产生ACK应答 void IIC_Ack(void) { SCL_LOW(); SDA_OUT(); SDA_LOW(); I2C_DELAY(2); SCL_HIGH(); I2C_DELAY(2); SCL_LOW(); } //不产生ACK应答 void IIC_NAck(void) { SCL_LOW(); SDA_OUT(); SDA_HIGH(); I2C_DELAY(2); SCL_HIGH(); I2C_DELAY(2); SCL_LOW(); } void IIC_Write_Byte(uint8_t data) { uint8_t i = 0; SDA_OUT(); SCL_LOW(); for(i=0; i<8; i++) { if(data & 0x80 ) SDA_HIGH(); else SDA_LOW(); data <<= 1; I2C_DELAY(2); SCL_HIGH(); I2C_DELAY(2); SCL_LOW(); I2C_DELAY(2); } } // ack = 1，发送 ACK // ack = 0，发送 nACK uint8_t IIC_Read_Byte(uint8_t ack) { uint8_t i = 0, data = 0; SDA_IN(); for(i = 0; i < 8; i++) { SCL_LOW(); I2C_DELAY(2); SCL_HIGH(); data <<= 1; if(SDA_READ()) data++; I2C_DELAY(1); } if(!ack) IIC_NAck(); else IIC_Ack(); return data; } void IIC_Write_UINT16(uint8_t dev_addr, uint8_t wr_addr, uint16_t data) { IIC_Start(); IIC_Write_Byte(dev_addr); IIC_Wait_Ack(); IIC_Write_Byte(wr_addr); IIC_Wait_Ack(); IIC_Write_Byte(data >> 8); IIC_Wait_Ack(); IIC_Write_Byte(data & 0xFF); IIC_Wait_Ack(); IIC_Stop(); I2C_DELAY(800); } uint16_t IIC_Read_UINT16(uint8_t dev_addr, uint8_t rd_addr) { uint16_t data; IIC_Start(); IIC_Write_Byte(dev_addr); IIC_Wait_Ack(); IIC_Write_Byte(rd_addr); IIC_Wait_Ack(); IIC_Start(); IIC_Write_Byte(dev_addr + 1); IIC_Wait_Ack(); data = IIC_Read_Byte(1); data = (data <<8 ) + IIC_Read_Byte(0); IIC_Stop(); return data; }
- iic_ctrl.h
/** * Copyright (c) 2022-2023，HelloAlpha * * Change Logs: * Date Author Notes */ #ifndef __I2C_CTRL_H__ #define __I2C_CTRL_H__ #include "iic_io.h" void IIC_Start(void); void IIC_Stop(void); uint8_t IIC_Wait_Ack(void); void IIC_Ack(void); void IIC_NAck(void); void IIC_Write_Byte(uint8_t value ); uint8_t IIC_Read_Byte(uint8_t addr); void IIC_Write_UINT16(uint8_t dev_addr, uint8_t wr_addr, uint16_t data); uint16_t IIC_Read_UINT16(uint8_t dev_addr, uint8_t rd_addr); #endif
软件模拟 IIC 最大的优点就在于方便移植，但相对于硬件 IIC 来说，模拟 IIC 通信速率要慢得多。
- 自问：那为啥不用硬件 IIC
- 自答：就想用模拟的嘿嘿嘿
