PX4-Autopilot/src/modules/uavcan/sensors/baro.cpp

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

#include "baro.hpp"
#include <drivers/device/ringbuffer.h>
#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_pressure_data(node),
	_sub_air_temperature_data(node),
	_reports(nullptr)
{
	last_temperature = 0.0f;
}

int UavcanBarometerBridge::init()
{
	int res = device::CDev::init();

	if (res < 0) {
		return res;
	}

	/* allocate basic report buffers */
	_reports = new RingBuffer(2, sizeof(baro_report));

	if (_reports == nullptr) {
		return -1;
	}

	res = _sub_air_pressure_data.start(AirPressureCbBinder(this, &UavcanBarometerBridge::air_pressure_sub_cb));

	if (res < 0) {
		log("failed to start uavcan sub: %d", res);
		return res;
	}

	res = _sub_air_temperature_data.start(AirTemperatureCbBinder(this, &UavcanBarometerBridge::air_temperature_sub_cb));

	if (res < 0) {
		log("failed to start uavcan sub: %d", res);
		return res;
	}

	return 0;
}

ssize_t UavcanBarometerBridge::read(struct file *filp, char *buffer, size_t buflen)
{
	unsigned count = buflen / sizeof(struct baro_report);
	struct baro_report *baro_buf = reinterpret_cast<struct baro_report *>(buffer);
	int ret = 0;

	/* buffer must be large enough */
	if (count < 1) {
		return -ENOSPC;
	}

	while (count--) {
		if (_reports->get(baro_buf)) {
			ret += sizeof(*baro_buf);
			baro_buf++;
		}
	}

	/* if there was no data, warn the caller */
	return ret ? ret : -EAGAIN;
}

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;
		}

	case SENSORIOCSPOLLRATE: {
			// not supported yet, pretend that everything is ok
			return OK;
		}

	case SENSORIOCSQUEUEDEPTH: {
			/* lower bound is mandatory, upper bound is a sanity check */
			if ((arg < 1) || (arg > 100)) {
				return -EINVAL;
			}

			irqstate_t flags = irqsave();

			if (!_reports->resize(arg)) {
				irqrestore(flags);
				return -ENOMEM;
			}

			irqrestore(flags);

			return OK;
		}

	default: {
			return CDev::ioctl(filp, cmd, arg);
		}
	}
}

void UavcanBarometerBridge::air_temperature_sub_cb(const
		uavcan::ReceivedDataStructure<uavcan::equipment::air_data::StaticTemperature> &msg)
{
	last_temperature = msg.static_temperature;
}

void UavcanBarometerBridge::air_pressure_sub_cb(const
		uavcan::ReceivedDataStructure<uavcan::equipment::air_data::StaticPressure> &msg)
{
	baro_report report;

	report.timestamp   = msg.getMonotonicTimestamp().toUSec();
	report.temperature = last_temperature;
	report.pressure    = msg.static_pressure / 100.0F;  // Convert to millibar
	report.error_count = 0;

	/*
	 * 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;

	// add to the ring buffer
	_reports->force(&report);

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