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131 lines
3.2 KiB
131 lines
3.2 KiB
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- |
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/* |
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This program is free software: you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation, either version 3 of the License, or |
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(at your option) any later version. |
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with this program. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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/* |
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backend driver for airspeed from a I2C MS4525D0 sensor |
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*/ |
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#include <AP_Common.h> |
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#include <AP_HAL.h> |
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#include <AP_Math.h> |
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#include <AP_Airspeed_I2C.h> |
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extern const AP_HAL::HAL& hal; |
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#define I2C_ADDRESS_MS4525DO 0x28 |
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// probe and initialise the sensor |
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bool AP_Airspeed_I2C::init(void) |
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{ |
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// get pointer to i2c bus semaphore |
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AP_HAL::Semaphore* i2c_sem = hal.i2c->get_semaphore(); |
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// take i2c bus sempahore |
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if (!i2c_sem->take(200)) |
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return false; |
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_measure(); |
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hal.scheduler->delay(10); |
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_collect(); |
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i2c_sem->give(); |
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if (_last_sample_time_ms != 0) { |
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hal.scheduler->register_timer_process(AP_HAL_MEMBERPROC(&AP_Airspeed_I2C::_timer)); |
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return true; |
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} |
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return false; |
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} |
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// start a measurement |
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void AP_Airspeed_I2C::_measure(void) |
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{ |
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_measurement_started_ms = 0; |
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if (hal.i2c->writeRegisters(I2C_ADDRESS_MS4525DO, 0, 0, NULL) == 0) { |
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_measurement_started_ms = hal.scheduler->millis(); |
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} |
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} |
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// read the values from the sensor |
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void AP_Airspeed_I2C::_collect(void) |
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{ |
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uint8_t data[4]; |
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_measurement_started_ms = 0; |
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if (hal.i2c->read(I2C_ADDRESS_MS4525DO, 4, data) != 0) { |
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return; |
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} |
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uint8_t status = data[0] & 0xC0; |
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if (status == 2) { |
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return; |
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} else if (status == 3) { |
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return; |
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} |
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int16_t dp_raw, dT_raw; |
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dp_raw = (data[0] << 8) + data[1]; |
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dp_raw = 0x3FFF & dp_raw; |
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dT_raw = (data[2] << 8) + data[3]; |
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dT_raw = (0xFFE0 & dT_raw) >> 5; |
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_temperature = ((200 * dT_raw) / 2047) - 50; |
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_pressure = fabs(dp_raw - (16384 / 2.0f)); |
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_last_sample_time_ms = hal.scheduler->millis(); |
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} |
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// 1kHz timer |
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void AP_Airspeed_I2C::_timer(void) |
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{ |
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AP_HAL::Semaphore* i2c_sem = hal.i2c->get_semaphore(); |
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if (!i2c_sem->take_nonblocking()) |
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return; |
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if (_measurement_started_ms == 0) { |
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_measure(); |
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i2c_sem->give(); |
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return; |
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} |
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if ((hal.scheduler->millis() - _measurement_started_ms) > 10) { |
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_collect(); |
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// start a new measurement |
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_measure(); |
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} |
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i2c_sem->give(); |
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} |
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// return the current differential_pressure in Pascal |
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bool AP_Airspeed_I2C::get_differential_pressure(float &pressure) |
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{ |
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if ((hal.scheduler->millis() - _last_sample_time_ms) > 100) { |
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return false; |
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} |
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pressure = _pressure; |
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return true; |
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} |
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// return the current temperature in degrees C, if available |
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bool AP_Airspeed_I2C::get_temperature(float &temperature) |
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{ |
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if ((hal.scheduler->millis() - _last_sample_time_ms) > 100) { |
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return false; |
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} |
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temperature = _temperature; |
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return true; |
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} |
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