気圧センサを使ってみた
RaspberryPi/pigpioでMPL115A1

void SendAndRecvCommand(
	const unsigned int spiHandle,
	const uint8_t command,
	uint8_t* readData)
{
	spiWrite(spiHandle, (char*)(&command), 1);
	spiRead(spiHandle, (char*)(readData), 1);
}
			

/**
 * Convert buffer data, data type is uint8_t, into float.
 *
 * @param[in]   buffer  Pointer to buffer conataining the uint8_t data.
 * @param   msbIndex    Index of buffer of MSB byte.
 * @param   lsbIndex    Index of buffer of LSB byte.
 * @param   floatLsb    LSB of float value.
 * @param   mask        Bit array to mask buffer. Default value is 0xFFFF.
 */
float Buff2Float(
		uint8_t* buffer,
		int msbIndex, int lsbIndex,
		float floatLsb,
		uint16_t mask = 0xFFFF)
{
	float converted = 0.0;

	uint16_t rawData = ((uint16_t)(buffer[msbIndex] << 8) + (uint16_t)(buffer[lsbIndex]));
	rawData &= mask;
	converted = (float)((int16_t)rawData * floatLsb);

	return converted;
}

/**
 * Read coefficient value..
 *
 * @param   spiHandle   SPI handle.
 */
void ReadCoefficient(const unsigned int spiHandle) {

	StartSequence();
	for (int buffIndex = 0; buffIndex < MPL115A1_DATA_INDEX_COEFF_MAX; buffIndex++) {
		SendAndRecvCommand(spiHandle, READ_COEFF_SEQ_COMMAND[buffIndex], &coefficientBuff[buffIndex]);
	}
	SendExtraCommand(spiHandle);
	StopSequence();

	//Setup coefficient from receive data.
	MPL_115A1_a0 = Buff2Float(
			coefficientBuff,
			MPL115A1_DATA_INDEX_COEFF_A0_MSB, MPL115A1_DATA_INDEX_COEFF_A0_LSB,
			MPL115A1_COEFF_A0_LSB);
	MPL_115A1_b1 = Buff2Float(
			coefficientBuff,
			MPL115A1_DATA_INDEX_COEFF_B1_MSB, MPL115A1_DATA_INDEX_COEFF_B1_LSB,
			MPL115A1_COEFF_B1_LSB);
	MPL_115A1_b2 = Buff2Float(
			coefficientBuff,
			MPL115A1_DATA_INDEX_COEFF_B2_MSB, MPL115A1_DATA_INDEX_COEFF_B2_LSB,
			MPL115A1_COEFF_B2_LSB);
	uint16_t rawData_c12 =
			((uint16_t)(coefficientBuff[MPL115A1_DATA_INDEX_COEFF_C12_MSB] << 8) +             (uint16_t)(coefficientBuff[MPL115A1_DATA_INDEX_COEFF_C12_LSB]));     rawData_c12 >>= 2;
	rawData_c12 &= 0x3FFF;
	MPL_115A1_c12 = (float)((int16_t)rawData_c12 * MPL115A1_COEFF_C12_LSB);
}

/**
 * Read pressure and temperature value.
 */
void ReadTempAndPress(const unsigned int spiHandle) {
	StartSequence();
	for (int buffIndex = 0; buffIndex < MPL115A1_DATA_INDEX_MAX; buffIndex++) {
		SendAndRecvCommand(spiHandle,
				READ_PRESS_TEMP_SEQ_COMMAND[buffIndex],
				(uint8_t*)(&dataBuff[buffIndex]));
	}
	SendExtraCommand(spiHandle);
	StopSequence();

	//Get Padc and Tadc value by buffer.
	{
		uint16_t rawData_padc =
				(((uint16_t)dataBuff[MPL115A1_DATA_INDEX_PRESS_MSB]) << 8) +                 dataBuff[MPL115A1_DATA_INDEX_PRESS_LSB];         rawData_padc >>= 6;
		MPL_115A1_padc = (float)((int16_t)rawData_padc);
	}
	{
		uint16_t rawData_tadc =
				(((uint16_t)dataBuff[MPL115A1_DATA_INDEX_TEMP_MSB]) << 8) +                 dataBuff[MPL115A1_DATA_INDEX_TEMP_LSB];         rawData_tadc >>= 6;
		MPL_115A1_tadc = (float)((int16_t)rawData_tadc);
	}
}

/**
 * Get pressure by reading data from the sensor.
 *
 * @return  Pressure specified by kPa.
 */
float GetPress() {
	float MPL_115A1_press_comp =
			MPL_115A1_a0 +
			(MPL_115A1_b1 + MPL_115A1_c12 * MPL_115A1_tadc) * MPL_115A1_padc +
			MPL_115A1_b2 * MPL_115A1_tadc;
	MPL_115A1_press = (MPL_115A1_press_comp * ((115.0 - 50.0) / 1023.0)) + 50.0;

	return MPL_115A1_press;
}