path: root/src/modules/uavcan/sensors/baro.cpp

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/**
 * @author Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#include "baro.hpp"
#include <cmath>

const char *const UavcanBarometerBridge::NAME = "baro";

UavcanBarometerBridge::UavcanBarometerBridge(uavcan::INode& node) :
UavcanCDevSensorBridgeBase("uavcan_baro", "/dev/uavcan/baro", BARO_BASE_DEVICE_PATH, ORB_ID(sensor_baro)),
_sub_air_data(node)
{
}

int UavcanBarometerBridge::init()
{
	int res = device::CDev::init();
	if (res < 0) {
		return res;
	}

	res = _sub_air_data.start(AirDataCbBinder(this, &UavcanBarometerBridge::air_data_sub_cb));
	if (res < 0) {
		log("failed to start uavcan sub: %d", res);
		return res;
	}
	return 0;
}

int UavcanBarometerBridge::ioctl(struct file *filp, int cmd, unsigned long arg)
{
	switch (cmd) {
	case BAROIOCSMSLPRESSURE: {
		if ((arg < 80000) || (arg > 120000)) {
			return -EINVAL;
		} else {
			log("new msl pressure %u", _msl_pressure);
			_msl_pressure = arg;
			return OK;
		}
	}
	case BAROIOCGMSLPRESSURE: {
		return _msl_pressure;
	}
	default: {
		return CDev::ioctl(filp, cmd, arg);
	}
	}
}

void UavcanBarometerBridge::air_data_sub_cb(const uavcan::ReceivedDataStructure<uavcan::equipment::air_data::StaticAirData> &msg)
{
	auto report = ::baro_report();

	report.timestamp   = msg.getMonotonicTimestamp().toUSec();
	report.temperature = msg.static_temperature;
	report.pressure    = msg.static_pressure / 100.0F;  // Convert to millibar

	/*
	 * Altitude computation
	 * Refer to the MS5611 driver for details
	 */
	const double T1 = 15.0 + 273.15; // temperature at base height in Kelvin
	const double a  = -6.5 / 1000;   // temperature gradient in degrees per metre
	const double g  = 9.80665;       // gravity constant in m/s/s
	const double R  = 287.05;        // ideal gas constant in J/kg/K

	const double p1 = _msl_pressure / 1000.0;      // current pressure at MSL in kPa
	const double p = double(msg.static_pressure) / 1000.0; // measured pressure in kPa

	report.altitude = (((std::pow((p / p1), (-(a * R) / g))) * T1) - T1) / a;

	publish(msg.getSrcNodeID().get(), &report);
}