#include "SHTxx.h"
#include "delay.h"
#include <math.h> //Keil library
#include <stdio.h> //Keil library
//********************************************************************
//产生IIC起始信号
static void IIC_Start(void)
{
SDA_OUT(); //sda线输出
IIC_SDA=1;
IIC_SCL=1;
delay_us(4);
IIC_SDA=0;//START:when CLK is high,DATA change form high to low
delay_us(4);
IIC_SCL=0;//钳住I2C总线，准备发送或接收数据
}
//产生IIC停止信号
static void IIC_Stop(void)
{
SDA_OUT();//sda线输出
IIC_SCL=0;
IIC_SDA=0;//STOP:when CLK is high DATA change form low to high
delay_us(4);
IIC_SCL=1;
IIC_SDA=1;//发送I2C总线结束信号
delay_us(4);
}
//等待应答信号到来
//返回值：1，接收应答失败
// 0，接收应答成功
static u8 IIC_Wait_Ack(void)
{
u16 ucErrTime=0;
SDA_IN(); //SDA设置为输入
IIC_SDA=1;delay_us(1);
IIC_SCL=1;delay_us(1);
while(READ_SDA)
{
ucErrTime++;
if(ucErrTime>60000)
{
IIC_Stop();
return 1;
}
}
IIC_SCL=0;//时钟输出0
return 0;
}
//产生ACK应答
static void IIC_Ack(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=0;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
//不产生ACK应答
static void IIC_NAck(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=1;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
//IIC发送一个字节
//返回从机有无应答
//1，有应答
//0，无应答
static void IIC_Send_Byte(u8 txd)
{
u8 t;
SDA_OUT();
IIC_SCL=0;//拉低时钟开始数据传输
for(t=0;t<8;t++)
{
IIC_SDA=(txd&0x80)>>7;
txd<<=1;
delay_us(2); //对TEA5767这三个延时都是必须的
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
delay_us(2);
}
}
//读1个字节，ack=1时，发送ACK，ack=0，发送nACK
static u8 IIC_Read_Byte(u8 ack)
{
u8 i,receive=0;
SDA_IN();//SDA设置为输入
for(i=0;i<8;i++ )
{
IIC_SCL=0;
delay_us(2);
IIC_SCL=1;
receive<<=1;
if(READ_SDA)receive++;
delay_us(1);
}
if (!ack)
IIC_NAck();//发送nACK
else
IIC_Ack(); //发送ACK
return receive;
}
//**********************************************************************
void SHT3x_Init(void)
{
RCC->APB2ENR|=1<<6; //使能PORTE时钟
GPIOE->CRL&=0XFF00FFFF; //PE4,PE5
GPIOE->CRL|=0X00330000;
GPIOE->ODR|=3<<4;
}
static etError SHT3x_StartWriteAccess(void)
{
u8 err;
IIC_Start();
IIC_Send_Byte(DevAddr<<1);
err=IIC_Wait_Ack();
return err;
}
static etError SHT3x_StartReadAccess(void)
{
u8 err;
IIC_Start();
IIC_Send_Byte((DevAddr<<1)|0x01);
err=IIC_Wait_Ack();
return err;
}
static etError SHT3x_StopAccess(void)
{
IIC_Stop();
return NO_ERROR;
}
//返回正确:0, 错误:非0
static etError SHT3x_WriteCmd(u16 cmd)
{
u8 err;
IIC_Send_Byte(cmd>>8); //写高字节
err=IIC_Wait_Ack();
if(err) return ACK_ERROR;
IIC_Send_Byte(cmd&0xff); //写低字节
err=IIC_Wait_Ack();
if(err) return ACK_ERROR;
else return NO_ERROR;
}
static u8 SHT3X_CalcCrc(u8 data[], u8 nbrOfBytes)
{
u8 bit; // bit mask
u8 crc = 0xFF; // calculated checksum
u8 byteCtr; // byte counter
// calculates 8-Bit checksum with given polynomial
for(byteCtr = 0; byteCtr < nbrOfBytes; byteCtr++)
{
crc ^= (data[byteCtr]);
for(bit = 8; bit > 0; --bit)
{
if(crc & 0x80) crc = (crc << 1) ^ POLYNOMIAL;
else crc = (crc << 1);
}
}
return crc;
}
static etError SHT3X_CheckCrc(u8 data[], u8 nbrOfBytes, u8 checksum)
{
u8 crc; // calculated checksum
// calculates 8-Bit checksum
crc = SHT3X_CalcCrc(data, nbrOfBytes);
// verify checksum
if(crc != checksum)
return CHECKSUM_ERROR;
else
return NO_ERROR;
}
float SHT3X_CalcTemperature(u16 rawValue)
{
// calculate temperature [°C]
// T = -45 + 175 * rawValue / (2^16-1)
return 175.0f * (float)rawValue / 65535.0f - 45.0f;
}
//-----------------------------------------------------------------------------
float SHT3X_CalcHumidity(u16 rawValue)
{
// calculate relative humidity [%RH]
// RH = rawValue / (2^16-1) * 100
return 100.0f * (float)rawValue / 65535.0f;
}
etError SHT3x_Read2ByteAndCrc(u16 *Res,u8 ack)
{
u8 Byte[2];
u8 checksum;
Byte[0]=IIC_Read_Byte(ACK);
Byte[1]=IIC_Read_Byte(ACK);
checksum=IIC_Read_Byte(ack); //读取crc
checksum=SHT3X_CheckCrc(Byte, 2,checksum);
*Res=(Byte[0]<<8)+Byte[1];
return checksum;
}
u8 SHT3x_ReadTempAndHumi(float *Temp,float* Humi)
{
u8 err;
u16 rawTemp,rawHumi;
err = SHT3x_StartWriteAccess();
err<<=2;
err+=SHT3x_WriteCmd(CMD_MEAS_CLOCKSTR_H);
SHT3x_StopAccess();
delay_ms(500);
err=SHT3x_StartReadAccess();
if(err)
SHT3x_StartReadAccess();
SHT3x_Read2ByteAndCrc(&rawTemp,ACK);
SHT3x_Read2ByteAndCrc(&rawHumi,NACK);
SHT3x_StopAccess();
*Temp=SHT3X_CalcTemperature(rawTemp);
*Humi=SHT3X_CalcHumidity(rawHumi);
return err;
}
