【CW32饭盒派开发板试用体验】+温度大气压检测

BMP085是一种用于温度、大气压检测的传感器，它采用I2C接口的方式来工作，可借助板载的I2C接口来直接进行插接，所使用的接口为J9，见图2所示。

图1传感器

图2 传感器接口

BMP085与开发板的连接关系为：

SCL---PB6

SDA---PB7

为便于引脚来输出高低电平及读取引脚的状态，为其引脚所作的相应定义为：

#define SCL_Set1() GPIO_WritePin(CW_GPIOB,
GPIO_PIN_6,GPIO_Pin_SET)

#define SCL_Clr1() GPIO_WritePin(CW_GPIOB,
GPIO_PIN_6,GPIO_Pin_RESET)

#define SDA_Set1() GPIO_WritePin(CW_GPIOB,
GPIO_PIN_7,GPIO_Pin_SET)

#define SDA_Clr1() GPIO_WritePin(CW_GPIOB, GPIO_PIN_7,GPIO_Pin_RESET)

#define SDA_IN GPIO_ReadPin(CW_GPIOB, GPIO_PIN_7)

配置所用引脚工作模式的函数为：

void BMP085_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStruct;
    __RCC_GPIOB_CLK_ENABLE();
    GPIO_InitStruct.IT = GPIO_IT_NONE; 
    GPIO_InitStruct.Mode= GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pins = GPIO_PIN_6| GPIO_PIN_7;
    GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
    GPIO_Init(CW_GPIOB,&GPIO_InitStruct);
}

BMP085的初始化函数为：

void Init_BMP085()
{    
ac1 = Multiple_read(0xAA);    
ac2 = Multiple_read(0xAC);    
ac3 = Multiple_read(0xAE);    
ac4 = Multiple_read(0xB0);    
ac5 = Multiple_read(0xB2);    
ac6 = Multiple_read(0xB4);    
b1 = Multiple_read(0xB6);    
b2 = Multiple_read(0xB8);    
mb = Multiple_read(0xBA);    
mc = Multiple_read(0xBC);
md = Multiple_read(0xBE);
}

以GPIO口实现字节数据发送的函数为：

void BMP085_Send_Byte(char txd)
{   
char t;   
OUTPUT_MODE_SET();   
SCL_Clr1();   
for(t=0;t<8;t++)
{       
if((txd&0x80)>>7)           
SDA_Set1();       
else           
SDA_Clr1();       
txd<<=1;       
SCL_Set1();       
SCL_Clr1();
}
}

以GPIO口实现字节数据接收的函数为：

char BMP085_Read_Byte(unsigned char ack)
{     
unsigned char i,receive=0;     
INPUT_MODE_SET();     
for(i=0;i<8;i++)     
{       
SCL_Clr1();       
SCL_Set1();       
receive<<=1;       
if(SDA_IN) receive++;
}   
if(!ack)       
BMP085_NAck();   
else       
BMP085_Ack();   
return receive;
}

BMP085读取温度的函数为：

long bmp085ReadTemp(void)
{   
BMP085_Start();   
BMP085_Send_Byte(BMP085_SlaveAddress);   
while(BMP085_Wait_Ack());   
BMP085_Send_Byte(0xF4);   
while(BMP085_Wait_Ack());   
BMP085_Send_Byte(0x2E);   
while(BMP085_Wait_Ack());   
BMP085_Stop();   
Delay(0xFFF);   
return (long) Multiple_read(0xF6);
}

BMP085读取大气压的函数为：

long bmp085ReadPressure(void)
{   
long pressure = 0;   
BMP085_Start();   
BMP085_Send_Byte(BMP085_SlaveAddress);   
while(BMP085_Wait_Ack()){}   
BMP085_Send_Byte(0xF4);   
while(BMP085_Wait_Ack()){}   
BMP085_Send_Byte(0x34);   
while(BMP085_Wait_Ack()){}
BMP085_Stop();   
Delay(0xFFF);   
pressure = Multiple_read(0xF6);   
pressure &= 0x0000FFFF;   
return pressure;
}

将检测值转化为实际物理单位的函数为：

void bmp085Convert()
{     
unsigned int ut;     
unsigned long up;     
long x1, x2, b5, b6, x3, b3, p;     
unsigned long b4, b7;     
ut = bmp085ReadTemp();     
up = bmp085ReadPressure();     
x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;     
x2 = ((long) mc << 11) / (x1 + md);     
b5 = x1 + x2;     
temperature1 = ((b5 + 8) >> 4);     
b6 = b5 - 4000;     
x1 = (b2 * (b6 * b6)>>12)>>11;     
x2 = (ac2 * b6)>>11;     
x3 = x1 + x2;     
b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;     
x1 = (ac3 * b6)>>13;     
x2 = (b1 * ((b6 * b6)>>12))>>16;     
x3 = ((x1 + x2) + 2)>>2;     
b4 = (ac4 * (unsigned long)(x3 + 32768))>>15;     
b7 = ((unsigned long)(up - b3) * (50000>>OSS));     
if (b7 < 0x80000000)       
p = (b7<<1)/b4;     
else       
p = (b7/b4)<<1;     
x1 = (p>>8) * (p>>8);     
x1 = (x1 * 3038)>>16;     
x2 = (-7357 * p)>>16;     
pressure = p+((x1 + x2 + 3791)>>4);
}

在TFT显示屏的配合下，实现温度与大气压检测的主程序为：

int32_t main(void)
{   
             RCC_HSI_Enable(RCC_HSIOSC_DIV6);
             Lcd_Init();
             Lcd_Clear(RED);
             Gui_DrawFont_GBK16(20,20,GRAY0,RED,"BMP085
Test");
             Gui_DrawFont_GBK16(20,60,GRAY0,RED,"Temp:(C)");
             Gui_DrawFont_GBK16(20,100,GRAY0,RED,"Pres:(KP)"); 
             Gui_DrawFont_GBK16(20,140,GRAY0,RED,"jinglixixi");
             Gui_DrawLine(0,136,127,136,GRAY0);
             BMP085_Init();  
             Init_BMP085();
             Delay(0xFFFF);
             Delay(0xFFFF);
             while(1)   
             {
                    bmp085Convert();  
                    ShowNum(20,80,GRAY0,RED,temperature1/10,3);       
                    ShowNum(20,120,GRAY0,RED,pressure/100,4);
                    Delay(0xFFFF);
                    Delay(0xFFFF);      
             }
}

经程序的编译和下载，其运行效果如图3所示。至此，就实现了对所处环境下的温度与大气压的检测功能。

图3 检测效果