前言
由于iic协议的通信频率不是特别高, 通过软件模拟的话, 在使用开发上, 整体会更加自由与方便。
更多详情,请直接参考飞利浦的iic协议手册。
代码范例
/**
******************************************************************************
* @file led configure
* @author wallea hu
* @brief
******************************************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "soft_i2c.h"
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define IIC_GPIO_CLK LL_IOP_GRP1_PERIPH_GPIOC
#define IIC_SCL_GPIOx GPIOC
#define SCL_PIN LL_GPIO_PIN_6
#define IIC_SDA_GPIOx GPIOC
#define SDA_PIN LL_GPIO_PIN_9
#define SCL_H LL_GPIO_SetOutputPin(IIC_SCL_GPIOx, SCL_PIN)
#define SCL_L LL_GPIO_ResetOutputPin(IIC_SCL_GPIOx, SCL_PIN)
#define SDA_H LL_GPIO_SetOutputPin(IIC_SDA_GPIOx, SDA_PIN)
#define SDA_L LL_GPIO_ResetOutputPin(IIC_SDA_GPIOx, SDA_PIN)
#define SCL_READ LL_GPIO_IsInputPinSet(IIC_SCL_GPIOx, SCL_PIN)
#define SDA_READ LL_GPIO_IsInputPinSet(IIC_SDA_GPIOx, SDA_PIN)
/* Private variables ---------------------------------------------------------*/
/* Private function -----------------------------------------------*/
/**
* @brief This function configures IIC Delay for multi-NOP
* @param None
* @retval None
*/
#define I2C_DELAY_COUNT 20 // ~= 19.41khz
__STATIC_INLINE void I2C_DELAY(void){
int tmp_i2c_elay_count = I2C_DELAY_COUNT;
do{
__NOP;
__NOP;
}while(tmp_i2c_elay_count--);
}
/**
* @brief This function configures IIC GPIO init
* @param None
* @retval None
*/
void Configure_SOFT_IIC_GPIO()
{
/* Enable the GPIOC Clock */
LL_IOP_GRP1_EnableClock(IIC_GPIO_CLK);
/* Configure SCL Pin as : High Speed, Open drain, Pull up */
LL_GPIO_SetPinMode(IIC_SCL_GPIOx, SCL_PIN, LL_GPIO_MODE_OUTPUT);
LL_GPIO_SetPinSpeed(IIC_SCL_GPIOx, SCL_PIN, LL_GPIO_SPEED_FREQ_HIGH);
LL_GPIO_SetPinOutputType(IIC_SCL_GPIOx, SCL_PIN, LL_GPIO_OUTPUT_OPENDRAIN);
LL_GPIO_SetPinPull(IIC_SCL_GPIOx, SCL_PIN, LL_GPIO_PULL_UP);
/* Configure SDA Pin as : High Speed, Open drain, Pull up */
LL_GPIO_SetPinMode(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_MODE_OUTPUT);
LL_GPIO_SetPinSpeed(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_SPEED_FREQ_HIGH);
LL_GPIO_SetPinOutputType(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_OUTPUT_OPENDRAIN);
LL_GPIO_SetPinPull(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_PULL_UP);
SCL_H;
SDA_H;
I2C_DELAY();
}
/**
* @brief This function configures i2c pin for input or output.
* @param None
* @retval None
*/
#define I2C_SET_SDA_IN LL_GPIO_SetPinMode(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_MODE_INPUT)
#define I2C_SET_SDA_OUT LL_GPIO_SetPinMode(IIC_SDA_GPIOx, SDA_PIN, LL_GPIO_MODE_OUTPUT)
/**
* @brief This function configures IIC Start
* @param None
* @retval None
*/
int I2C_Start(void)
{
I2C_SET_SDA_OUT;
SDA_H;
SCL_H;
I2C_DELAY();
if(!SDA_READ)
{
return 0;
}
SDA_L;
I2C_DELAY();
if(SDA_READ)
{
return 0;
}
SCL_L;
return 1;
}
/**
* @brief This function configures IIC Stop
* @param None
* @retval None
*/
void I2C_Stop(void)
{
I2C_SET_SDA_OUT;
//SCL_L;
SDA_L;
SCL_H;
I2C_DELAY();
SDA_H;
I2C_DELAY();
}
/**
* @brief This function configures IIC Ack
* @param None
* @retval None
*/
static void I2C_Ack()
{
SCL_L;
I2C_SET_SDA_OUT;
SDA_L;
I2C_DELAY();
SCL_H;
I2C_DELAY();
SCL_L;
}
/**
* @brief This function configures IIC NoAck
* @param None
* @retval None
*/
static void I2C_NoAck()
{
SCL_L;
I2C_SET_SDA_OUT;
I2C_DELAY();
SDA_H;
I2C_DELAY();
SCL_H;
I2C_DELAY();
SCL_L;
}
/**
* @brief This function configures IIC getAck
* @param None
* @retval None
*/
uint8_t I2C_GetAck(void)
{
uint8_t times = 0;
I2C_SET_SDA_IN;
SDA_H;
SCL_H;
I2C_DELAY();
while(SDA_READ)
{
times++;
if(times> 250)
{
SCL_L;
return 0;
}
}
SCL_L;
return 1;
}
/**
* @brief This function configures IIC write data.
* @param None
* @retval None
*/
void I2C_WriteByte(uint8_t Data)
{
uint8_t cnt = 0;
I2C_SET_SDA_OUT;
for(cnt=0; cnt<8; cnt++)
{
SCL_L;
I2C_DELAY();
if(Data & 0x80)
{
SDA_H;
}
else
{
SDA_L;
}
Data <<= 1;
SCL_H;
I2C_DELAY();
}
SCL_L;
I2C_DELAY();
}
/**
* @brief This function configures IIC read byte
* @param None
* @retval None
*/
uint8_t I2C_ReadByte(uint8_t ack)
{
uint8_t cnt = 0;
static uint8_t data = 0;
data = 0;
I2C_SET_SDA_IN;
for(cnt=0; cnt<8; cnt++)
{
SCL_L;
I2C_DELAY();
SCL_H;
data <<= 1;
if(SDA_READ)
{
data |= 0x01;
}
I2C_DELAY();
}
if(ack == 1)
{
I2C_NoAck();
}
else
{
I2C_Ack();
}
return data;
}
/**
* @brief a common method for writing device .
* @param None
* @retval None
*/
int Common_WriteByte(uint16_t device, uint16_t addr, uint8_t data)
{
I2C_Start();
I2C_WriteByte(device << 1 | 0x00);
if(!I2C_GetAck())
{
I2C_Stop();
return 0;
}
I2C_WriteByte((uint8_t)(addr&0x00FF));
I2C_GetAck();
I2C_WriteByte(data);
I2C_GetAck();
I2C_Stop();
return 1;
}
/**
* @brief a common method for reading device.
* @param None
* @retval None
*/
int Common_ReadByte(uint16_t device, uint16_t addr, uint8_t *data)
{
I2C_Start();
I2C_WriteByte(device << 1 | 0x00);
if(!I2C_GetAck())
{
I2C_Stop();
return 0;
}
I2C_WriteByte((uint8_t)(addr & 0x00FF));
I2C_GetAck();
I2C_Start();
I2C_WriteByte(device << 1 | 0x01);
if(!I2C_GetAck())
{
I2C_Stop();
return 0;
}
*data = I2C_ReadByte(1);
I2C_Stop();
return 1;
}
/************************ (C) COPYRIGHT wallea Hu *****END OF FILE****/
使用注意点:
- 主机读写从机的时候, 总线的时钟由主机来控制产生。
- iic的引脚使用开漏输出,需要默认上拉,用推挽会导致mos出现短路现象, 上拉的时候,表示总线空闲, 下拉的时候,表示有效电平,
在主从应答的时候,便需要下拉为低电平。 - 在进行读写操作时, 如果主机需要对从机继续操作的时候, 需要对从机进行ack,
而如果不需要的话, 务必先发送nack信号, 再发送stop信号,否则有些从机会莫名死机或者影响后续的读写操作。 - 在写数据的时候, 每写一次,要通过发送时钟, 读一下ack信号, 否则总线容易异常。
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