使用STM32F103 I2C驱动SHT30

SHT30的官方代码见《Sensirion_Humidity_Sensors_SHT3x_Sample_Code_V2》，不过官方是用GPIO模拟的I2C时序，现在修改为STM32F103的硬件I2C驱动SHT30.

使用STM32F103的I2C1实现该功能，相关头文件定义如下：

#define SHT30_I2C                            I2C1#define SHT30_I2C_ADDR                     (0x44) #define SHT30_I2C_SCL_PIN                  (GPIO_Pin_6)           /* PB.06 */
#define SHT30_I2C_SCL_GPIO_PORT            (GPIOB)#define SHT30_I2C_SDA_PIN                  (GPIO_Pin_7)           /* PB.07 */
#define SHT30_I2C_SDA_GPIO_PORT            (GPIOB)#define I2C_SPEED               100000U

官方代码在while(1)里调用SHT3X_GetTempAndHumi函数获取温湿度值（时钟延伸模式）：
//-----------------------------------------------------------------------------

while(1){SHT3X_GetTempAndHumi(&temperature, &humidity, REPEATAB_HIGH, MODE_CLKSTRETCH, 50);printf("temperature=%.1f℃\thumidity=%.1f%%RH\terror=%d\r\n",(float)temperature,(float)humidity,(u8)error);}

根据产品实际需求，在需要获取温湿度时调用SHT3X_GetTempAndHumi()函数即可。

//-----------------------------------------------------------------------------
1:获取温湿度函数SHT3X_GetTempAndHumi()

etError SHT3X_GetTempAndHumi(ft* temperature, ft* humidity,etRepeatability repeatability, etMode mode, u8t timeout)
{etError error;switch(mode){case MODE_CLKSTRETCH: // get temperature with clock stretching mode error = SHT3X_GetTempAndHumiClkStretch(temperature, humidity,repeatability, timeout);break;case MODE_POLLING:  // get temperature with polling mode error = SHT3X_GetTempAndHumiPolling(temperature, humidity,repeatability, timeout);break; default:error = PARM_ERROR; break;}return error;
}

由于我们使用的是MODE_CLKSTRETCH时钟延伸模式，因此只修改SHT3X_GetTempAndHumiClkStretch函数。

2:用时钟延伸模式获取温湿度函数SHT3X_GetTempAndHumiClkStretch();

//-----------------------------------------------------------------------------
etError SHT3X_GetTempAndHumiClkStretch(ft* temperature, ft* humidity,etRepeatability repeatability, u8t timeout)
{etError error; // error codeu16t   rawValueTemp; // temperature raw value from sensor u16t rawValueHumi; // humidity raw value from sensorerror = SHT3X_StartWriteAccess();// if no error ...if(error == NO_ERROR){// start measurement in clock stretching mode// use depending on the required repeatability, the corresponding commandswitch(repeatability){case REPEATAB_LOW:error = SHT3X_WriteCommand(CMD_MEAS_CLOCKSTR_L); break;case REPEATAB_MEDIUM:error = SHT3X_WriteCommand(CMD_MEAS_CLOCKSTR_M); break;case REPEATAB_HIGH:error = SHT3X_WriteCommand(CMD_MEAS_CLOCKSTR_H); break;default:error = PARM_ERROR; break;}}// if no error, start read accessif(error == NO_ERROR) error = SHT3X_StartReadAccess();// if no error, read temperature raw valuesif(error == NO_ERROR) error = SHT3X_Read2BytesAndCrc(&rawValueTemp, ACK, timeout);// if no error, read humidity raw valuesif(error == NO_ERROR) error = SHT3X_Read2BytesAndCrc(&rawValueHumi, NACK, 0); //SHT3X_StopAccess();// if no error, calculate temperature in °C and humidity in %RHif(error == NO_ERROR){*temperature = SHT3X_CalcTemperature(rawValueTemp);*humidity = SHT3X_CalcHumidity(rawValueHumi);}else{SHT3X_StopAccess();}return error;
}

与官方源代码相比，修改了函数SHT3X_StopAccess()的定义及使用方式。官方源代码在接收到6个字节的温湿度数据后，调用SHT3X_StopAccess()模拟产生I2C通信停止条件。而硬件I2C(主接收模式)关闭通信则需要以下操作（RM0008中文参考手册P499）：

  主设备在从 从设备 接收到最后一个字节后发送一个NACK。接收到NACK后，从设备释放对SCL和SDA线的控制;主设备就可以发送一个停止/重起始条件.1:为了在收到最后一个字节后产生NACK脉冲，在读倒数第二个字节之后必须清除ACK位.2:为了产生一个停止/重起始条件,软件必须在读第二个数据字节之后设置STOP/START位.

主接收器传送序列图：

因此，应在接收最后一个字节之前添加通信停止代码，该代码会在I2c_ReadByte()函数里描述。

3:开始写入访问函数SHT3X_StartWriteAccess()。该函数先判断总线是否busy，不忙的话产生开始条件，再发送从机地址，然后等待从机应答。

//-----------------------------------------------------------------------------
static etError SHT3X_StartWriteAccess(void)
{etError error = NO_ERROR; // error code/*!< While the bus is busy */SHT30_Timeout = SHT30_LONG_TIMEOUT;while(I2C_GetFlagStatus(SHT30_I2C, I2C_FLAG_BUSY)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_ERROR;return error;}}I2C_AcknowledgeConfig(SHT30_I2C, ENABLE);//I2c_StartCondition();// write a start condition I2C_GenerateSTART(SHT30_I2C, ENABLE);/*!< Test on EV5 and clear it (cleared by reading SR1 then writing to DR) *//** * @brief  Communication start* * After sending the START condition (I2C_GenerateSTART() function) the master * has to wait for this event. It means that the Start condition has been correctly * released on the I2C bus (the bus is free, no other devices is communicating).* */SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C, I2C_EVENT_MASTER_MODE_SELECT)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV5_ERROR;return error;}}// write the sensor I2C address with the write flag //error = I2c_WriteByte(_i2cAddress << 1);//发送地址后，等待从机确认 EV6I2C_Send7bitAddress(SHT30_I2C, (SHT30_I2C_ADDR << 1), I2C_Direction_Transmitter);/*!< Test on EV6 and clear it */ SHT30_Timeout = SHT30_LONG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV6_ERROR;return error;}}return error;
}//-----------------------------------------------------------------------------

4：写命令函数SHT3X_WriteCommand()
从机应答主机地址后，SHT3X_WriteCommand()函数开始写命令，先发送高字节，再发生低字节。每个字节发送后均要等待从机应答。发送完成后，主机产生停止信号。

//-----------------------------------------------------------------------------
static etError SHT3X_WriteCommand(etCommands command)
{etError error = NO_ERROR; // error code// write the upper 8 bits of the command to the sensor //error = I2c_WriteByte(command >> 8);I2C_SendData(SHT30_I2C,command >> 8);/* --EV8 */SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C,I2C_EVENT_MASTER_BYTE_TRANSMITTED)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV8_ERROR;return error;}}// write the lower 8 bits of the command to the sensor //error |= I2c_WriteByte(command & 0x00FF);I2C_SendData(SHT30_I2C,command & 0x00FF);SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C,I2C_EVENT_MASTER_BYTE_TRANSMITTED))//EV8_2{if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV8_ERROR;return error;}}I2C_GenerateSTOP(SHT30_I2C, ENABLE);//主发送器通信完成return error;
}

5:开始读访问SHT3X_StartReadAccess()

//-----------------------------------------------------------------------------
static etError SHT3X_StartReadAccess(void)
{etError error; // error code// write a start condition //I2c_StartCondition();/*!< While the bus is busy */SHT30_Timeout = SHT30_LONG_TIMEOUT;while(I2C_GetFlagStatus(SHT30_I2C, I2C_FLAG_BUSY)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_ERROR;return error;}}// write a start condition //I2c_StartCondition();//EV5:After sending the START condition (I2C_GenerateSTART() function) the master //has to wait for this event.I2C_GenerateSTART(SHT30_I2C, ENABLE);/*!< Test on EV5 and clear it (cleared by reading SR1 then writing to DR) */SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C, I2C_EVENT_MASTER_MODE_SELECT)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV5_ERROR;return error;}}// write the sensor I2C address with the write flag //error = I2c_WriteByte(_i2cAddress << 1);//发送地址后，等待从机确认 EV6I2C_Send7bitAddress(SHT30_I2C, (SHT30_I2C_ADDR << 1), I2C_Direction_Receiver);/*!< Test on EV6 and clear it */ SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV6_ERROR;return error;}}// write the sensor I2C address with the read flag //error = I2c_WriteByte(_i2cAddress << 1 | 0x01);return error;
}

6:读取两个字节数据和Crc:SHT3X_Read2BytesAndCrc()和官方代码一样。

//-----------------------------------------------------------------------------
static etError SHT3X_Read2BytesAndCrc(u16t* data, etI2cAck finaleAckNack,u8t timeout)
{etError error; // error codeu8t    bytes[2]; // read data array u8t    checksum; // checksum byte// read two data bytes and one checksum byteerror = I2c_ReadByte(&bytes[0], ACK, timeout);if(error == NO_ERROR) error = I2c_ReadByte(&bytes[1], ACK, 0);if(error == NO_ERROR) error = I2c_ReadByte(&checksum, finaleAckNack, 0);// verify checksumif(error == NO_ERROR) error = SHT3X_CheckCrc(bytes, 2, checksum);// combine the two bytes to a 16-bit value*data = (bytes[0] << 8) | bytes[1];return error;
}

7:读去字节I2c_ReadByte()
为了防止读取数据时，任务被中断打断导致数据出错，读取时先关闭中断，读取完成后，再开启中断。

etError I2c_ReadByte(u8t *rxByte, etI2cAck ack, u8t timeout)
{etError error = NO_ERROR; __set_PRIMASK(1);//关总中断if(ack == ACK){I2C_AcknowledgeConfig(SHT30_I2C, ENABLE);}else{//关闭通信:/* 主设备在从 从设备 接收到最后一个字节后发送一个NACK。接收到NACK后，从设备* 释放对SCL和SDA线的控制;主设备就可以发送一个停止/重起始条件.* 1:为了在收到最后一个字节后产生NACK脉冲，在读倒数第二个字节之后必须清除ACK位.* 2:为了产生一个停止/重起始条件,软件必须在读第二个数据字节之后设置STOP/START位.*/I2C_AcknowledgeConfig(SHT30_I2C, DISABLE);(void)SHT30_I2C->SR2;I2C_GenerateSTOP(SHT30_I2C, ENABLE);}//从机端接收到主机地址后，开始向主机发送数据/*!< Test on EV7 */ SHT30_Timeout = SHT30_LONG_TIMEOUT;while(!I2C_CheckEvent(SHT30_I2C, I2C_EVENT_MASTER_BYTE_RECEIVED)){if((SHT30_Timeout--) == 0) {error = TIMEOUT_EV7_ERROR;return error;}}*rxByte  = I2C_ReceiveData(SHT30_I2C);if(ack == NACK){/* Wait to make sure that STOP control bit has been cleared *///STOP位：监测到停止条件时，由硬件清除。SHT30_Timeout = SHT30_FLAG_TIMEOUT;while(SHT30_I2C->CR1 & I2C_CR1_STOP){if((SHT30_Timeout--) == 0) {error = TIMEOUT_ERROR;return error;}}}__set_PRIMASK(0);//开总中断return error;      //return with no error
}

8:SHT3X_CheckCrc()和官方代码一样。

//-----------------------------------------------------------------------------
static etError SHT3X_CheckCrc(u8t data[], u8t nbrOfBytes, u8t checksum)
{u8t crc;   // calculated checksum// calculates 8-Bit checksumcrc = SHT3X_CalcCrc(data, nbrOfBytes);// verify checksumif(crc != checksum) return CHECKSUM_ERROR; else return NO_ERROR;
}

9:SHT3X_StopAccess()
修改了SHT3X_StopAccess函数的内容及使用方式，当检测到有ERROR时，调用该函数，重新初始化I2C。

static void SHT3X_StopAccess(void)
{I2C_DeInit(SHT30_I2C);SHT30_Init(SHT30_I2C_ADDR);
}

10： I2C配置:SHT30_Init()

void SHT30_Init(uint8_t i2cAddress)
{I2C_InitTypeDef  I2C_InitStructure;GPIO_InitTypeDef  GPIO_InitStructure;/*配置时钟*/RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB|RCC_APB2Periph_AFIO, ENABLE);GPIO_InitStructure.GPIO_Pin = SHT30_I2C_SCL_PIN|SHT30_I2C_SDA_PIN;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;GPIO_Init(SHT30_I2C_SCL_GPIO_PORT, &GPIO_InitStructure);/*!< SHT30_I2C Periph clock enable */RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE); I2C_DeInit(I2C1);/*!< I2C configuration */I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;I2C_InitStructure.I2C_OwnAddress1 = i2cAddress;I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;I2C_InitStructure.I2C_ClockSpeed = I2C_SPEED;/* Apply I2C configuration after enabling it */I2C_Init(I2C1, &I2C_InitStructure);/* I2C Peripheral Enable */I2C_Cmd(I2C1, ENABLE);
}

起始条件+地址+写命令+命令码高字节：

命令码低字节+停止条件+起始条件+地址+读命令+时钟延伸(等待转换结果)：

获取的温湿度值：

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使用STM32F103 I2C驱动SHT30

使用STM32F103 I2C驱动SHT30

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