I2C是个让人又爱又恨的总线，一方面非常方便，只要上拉电压足够，一个I2C总线可以接多组I2C从机，二来，每个I2C器件对于时序和数据字节的要求又不尽相同，有些器件喜欢延时长一点，有些喜欢延时短一点，有些是8位器件地址+8位寄存器+8位数据，有些是8位器件地址+8位寄存器+16位数据，有些是寄存器不公开，直接是8位器件地址+N*8位数据，整合一个项目里面的所有I2C器件可是非常烦人的事，所以我就简单接个气压传感器BMP280就完事。
- uint8_t msb , lsb , xlsb;
- float var1 , var2;
- bmp280Calib bmp280Cal;
- uint8_t BMP280_Init(void)
- {
- uint8_t bmp280_id;
- uint8_t tmp[1];
- I2C_Read_Datas_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77, BMP280_CHIPID_REG, 1, &bmp280_id);
- printf("bmp280_id = 0x%xn" , bmp280_id);
- I2C_Read_Datas_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77, BMP280_DIG_T1_LSB_REG , 24 , (u8 *)&bmp280Cal);
-
- //printf("%d %d %d %d %d %d %d %d %d %d %d %dn" ,
- // bmp280Cal.dig_T1 , bmp280Cal.dig_T2 , bmp280Cal.dig_T3 ,
- // bmp280Cal.dig_P1 , bmp280Cal.dig_P2 , bmp280Cal.dig_P3 ,
- // bmp280Cal.dig_P4 , bmp280Cal.dig_P5 , bmp280Cal.dig_P6 ,
- // bmp280Cal.dig_P7 , bmp280Cal.dig_P8 , bmp280Cal.dig_P9);
- tmp[0] = BMP280_MODE;
- I2C_Write_Reg_Datas_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_CTRLMEAS_REG , 1 , tmp);
- tmp[0] = 5 << 2;
- I2C_Write_Reg_Datas_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_CONFIG_REG , 1 , tmp);
- return bmp280_id;
- }
- float BMP280PressureToAltitude(float* pressure)
- {
- if (*pressure > 0)
- {
- return ((pow((1015.7f / (*pressure)), CONST_PF) - 1.0f) * (FIX_TEMP + 273.15f)) / 0.0065f;
- }
- else
- {
- return 0;
- }
- }
- void BMP280_Read_Pressure_Tempature(float * pres , float * temp)
- {
- msb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_PRESSURE_MSB_REG);
- lsb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_PRESSURE_LSB_REG);
- xlsb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_PRESSURE_XLSB_REG);
-
- *pres = (msb * 65536 | lsb * 256 | xlsb) >> 4;
- msb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_TEMPERATURE_MSB_REG);
- lsb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_TEMPERATURE_LSB_REG);
- xlsb = I2C_Read_Addr_PB6_PB7(BMP280_SLAVE_ADDRESS_0x77 , BMP280_TEMPERATURE_XLSB_REG);
- *temp = (msb * 65536 | lsb * 256 | xlsb) >> 4;
- var1 = ((*temp) / 16384.0 - bmp280Cal.dig_T1 / 1024.0)*(bmp280Cal.dig_T2);
- var2 = (((*temp) / 131072.0 - bmp280Cal.dig_T1 / 8192.0) *
- ((*temp) / 131072.0 - bmp280Cal.dig_T1 / 8192.0)) * bmp280Cal.dig_T3;
- *temp = var1 + var2;
- *temp /= 5120.0;
- var1 = ((*temp) / 2.0) - 64000.0;
- var2 = var1 * var1*(bmp280Cal.dig_P6) / 32768.0;
- var2 = var2 + var1 * (bmp280Cal.dig_P5)*2.0;
- var2 = (var2 / 4.0) + ((bmp280Cal.dig_P4)*65536.0);
- var1 = (bmp280Cal.dig_P3)*var1*var1 / 524288.0 + (bmp280Cal.dig_P2)*var1 / 524288.0;
- var1 = (1.0 + var1 / 32768.0)*(bmp280Cal.dig_P1);
- *pres = 1048576.0 - (*pres);
- *pres = ((*pres) - (var2 / 4096.0))*6250.0 / var1;
- var1 = (bmp280Cal.dig_P9) * (*pres) * (*pres) / 2147483648.0;
- var2 = (*pres) * (bmp280Cal.dig_P8) / 32768.0;
- *pres = (*pres) + (var1 + var2 + (bmp280Cal.dig_P7)) / 16.0;
- }
