MPL3115A2 I2C Communication Flow

Startup Flow

1. main() initializes GPIO, I2C1, and USART1.
2. main() calls MPL3115A2_Init().
3. The driver calls HAL_I2C_IsDeviceReady().
4. If the sensor does not respond, reset_I2C() clocks SCL manually and reinitializes I2C1.
5. The driver reads WHO_AM_I and expects 0xC4.
6. The driver places the sensor in standby before configuration changes.
7. The driver enables pressure and temperature data-ready flags.
8. The driver enables active barometer mode with OSR=128.

Measurement Flow

Temperature:

• main() polls the STATUS register for the temperature data-ready bit.
• MPL3115A2_ReadTemperature() reads OUT_T_MSB and OUT_T_LSB.
• The raw signed 12-bit fixed-point value is converted to degrees Celsius.
• main() converts Celsius to Fahrenheit for serial output.

Pressure:

• main() polls the STATUS register for the pressure/temperature data-ready bit.
• MPL3115A2_ReadPressure() reads OUT_P_MSB, OUT_P_CSB, and OUT_P_LSB.
• The raw Q18.2 pressure value is converted from pascals to inches of mercury.