使用STM32F103 I2C驅動SHT30
SHT30的官方代碼見《Sensirion_Humidity_Sensors_SHT3x_Sample_Code_V2》，不過官方是用GPIO模擬的I2C時序，現在修改為STM32F103的硬體I2C驅動SHT30.
使用STM32F103的I2C1實作該功能，相關頭檔案定義如下：
#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
官方代碼在while(1)里呼叫SHT3X_GetTempAndHumi函式獲取溫濕度值（時鐘延伸模式）：
//-----------------------------------------------------------------------------
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);
}
根據產品實際需求，在需要獲取溫濕度時呼叫SHT3X_GetTempAndHumi()函式即可，
//-----------------------------------------------------------------------------
1:獲取溫濕度函式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;
}
由于我們使用的是MODE_CLKSTRETCH時鐘延伸模式，因此只修改SHT3X_GetTempAndHumiClkStretch函式，
2:用時鐘延伸模式獲取溫濕度函式SHT3X_GetTempAndHumiClkStretch();
//-----------------------------------------------------------------------------
etError SHT3X_GetTempAndHumiClkStretch(ft* temperature, ft* humidity,etRepeatability repeatability, u8t timeout)
{
etError error; // error code
u16t rawValueTemp; // temperature raw value from sensor
u16t rawValueHumi; // humidity raw value from sensor
error = SHT3X_StartWriteAccess();
// if no error ...
if(error == NO_ERROR)
{
// start measurement in clock stretching mode
// use depending on the required repeatability, the corresponding command
switch(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 access
if(error == NO_ERROR) error = SHT3X_StartReadAccess();
// if no error, read temperature raw values
if(error == NO_ERROR) error = SHT3X_Read2BytesAndCrc(&rawValueTemp, ACK, timeout);
// if no error, read humidity raw values
if(error == NO_ERROR) error = SHT3X_Read2BytesAndCrc(&rawValueHumi, NACK, 0);
//SHT3X_StopAccess();
// if no error, calculate temperature in °C and humidity in %RH
if(error == NO_ERROR)
{
*temperature = SHT3X_CalcTemperature(rawValueTemp);
*humidity = SHT3X_CalcHumidity(rawValueHumi);
}
else
{
SHT3X_StopAccess();
}
return error;
}
與官方源代碼相比，修改了函式SHT3X_StopAccess()的定義及使用方式，官方源代碼在接收到6個位元組的溫濕度資料后，呼叫SHT3X_StopAccess()模擬產生I2C通信停止條件，而硬體I2C(主接收模式)關閉通信則需要以下操作（RM0008中文參考手冊P499）：
主設備在從 從設備 接收到最后一個位元組后發送一個NACK，接收到NACK后，從設備釋放對SCL和SDA線的控制;主設備就可以發送一個停止/重起始條件.
1:為了在收到最后一個位元組后產生NACK脈沖，在讀倒數第二個位元組之后必須清除ACK位.
2:為了產生一個停止/重起始條件,軟體必須在讀第二個資料位元組之后設定STOP/START位.
主接收器傳送序列圖：
因此，應在接收最后一個位元組之前添加通信停止代碼，該代碼會在I2c_ReadByte()函式里描述，
3:開始寫入訪問函式SHT3X_StartWriteAccess()，該函式先判斷總線是否busy，不忙的話產生開始條件，再發送從機地址，然后等待從機應答，
//-----------------------------------------------------------------------------
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);
//發送地址后，等待從機確認 EV6
I2C_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：寫命令函式SHT3X_WriteCommand()
從機應答主機地址后，SHT3X_WriteCommand()函式開始寫命令，先發送高位元組，再發生低位元組，每個位元組發送后均要等待從機應答，發送完成后，主機產生停止信號，
//-----------------------------------------------------------------------------
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);//主發送器通信完成
return error;
}
5:開始讀訪問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);
//發送地址后，等待從機確認 EV6
I2C_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:讀取兩個位元組資料和Crc:SHT3X_Read2BytesAndCrc()和官方代碼一樣，
//-----------------------------------------------------------------------------
static etError SHT3X_Read2BytesAndCrc(u16t* data, etI2cAck finaleAckNack,u8t timeout)
{
etError error; // error code
u8t bytes[2]; // read data array
u8t checksum; // checksum byte
// read two data bytes and one checksum byte
error = 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 checksum
if(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:讀去位元組I2c_ReadByte()
為了防止讀取資料時，任務被中斷打斷導致資料出錯，讀取時先關閉中斷，讀取完成后，再開啟中斷，
etError I2c_ReadByte(u8t *rxByte, etI2cAck ack, u8t timeout)
{
etError error = NO_ERROR;
__set_PRIMASK(1);//關總中斷
if(ack == ACK)
{
I2C_AcknowledgeConfig(SHT30_I2C, ENABLE);
}
else
{
//關閉通信:
/* 主設備在從 從設備 接收到最后一個位元組后發送一個NACK，接收到NACK后，從設備
* 釋放對SCL和SDA線的控制;主設備就可以發送一個停止/重起始條件.
* 1:為了在收到最后一個位元組后產生NACK脈沖，在讀倒數第二個位元組之后必須清除ACK位.
* 2:為了產生一個停止/重起始條件,軟體必須在讀第二個資料位元組之后設定STOP/START位.
*/
I2C_AcknowledgeConfig(SHT30_I2C, DISABLE);
(void)SHT30_I2C->SR2;
I2C_GenerateSTOP(SHT30_I2C, ENABLE);
}
//從機端接收到主機地址后，開始向主機發送資料
/*!< 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：監測到停止條件時，由硬體清除，
SHT30_Timeout = SHT30_FLAG_TIMEOUT;
while(SHT30_I2C->CR1 & I2C_CR1_STOP)
{
if((SHT30_Timeout--) == 0)
{
error = TIMEOUT_ERROR;
return error;
}
}
}
__set_PRIMASK(0);//開總中斷
return error; //return with no error
}
8:SHT3X_CheckCrc()和官方代碼一樣，
//-----------------------------------------------------------------------------
static etError SHT3X_CheckCrc(u8t data[], u8t nbrOfBytes, u8t checksum)
{
u8t crc; // calculated checksum
// calculates 8-Bit checksum
crc = SHT3X_CalcCrc(data, nbrOfBytes);
// verify checksum
if(crc != checksum) return CHECKSUM_ERROR;
else return NO_ERROR;
}
9:SHT3X_StopAccess()
修改了SHT3X_StopAccess函式的內容及使用方式，當檢測到有ERROR時，呼叫該函式，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;
/*配置時鐘*/
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);
}
起始條件+地址+寫命令+命令碼高位元組：
命令碼低位元組+停止條件+起始條件+地址+讀命令+時鐘延伸(等待轉換結果)：
獲取的溫濕度值：
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