diff options
Diffstat (limited to 'src/drivers/meas_airspeed/meas_airspeed.cpp')
-rw-r--r-- | src/drivers/meas_airspeed/meas_airspeed.cpp | 248 |
1 files changed, 195 insertions, 53 deletions
diff --git a/src/drivers/meas_airspeed/meas_airspeed.cpp b/src/drivers/meas_airspeed/meas_airspeed.cpp index 06d89abf7..c0f3c28e0 100644 --- a/src/drivers/meas_airspeed/meas_airspeed.cpp +++ b/src/drivers/meas_airspeed/meas_airspeed.cpp @@ -79,12 +79,15 @@ #include <systemlib/param/param.h> #include <systemlib/perf_counter.h> +#include <mathlib/math/filter/LowPassFilter2p.hpp> + #include <drivers/drv_airspeed.h> #include <drivers/drv_hrt.h> #include <uORB/uORB.h> #include <uORB/topics/differential_pressure.h> #include <uORB/topics/subsystem_info.h> +#include <uORB/topics/system_power.h> #include <drivers/airspeed/airspeed.h> @@ -99,12 +102,14 @@ #define ADDR_READ_MR 0x00 /* write to this address to start conversion */ /* Measurement rate is 100Hz */ +#define MEAS_RATE 100.0f +#define MEAS_DRIVER_FILTER_FREQ 3.0f #define CONVERSION_INTERVAL (1000000 / 100) /* microseconds */ class MEASAirspeed : public Airspeed { public: - MEASAirspeed(int bus, int address = I2C_ADDRESS_MS4525DO, const char* path = PATH_MS4525); + MEASAirspeed(int bus, int address = I2C_ADDRESS_MS4525DO, const char *path = PATH_MS4525); protected: @@ -116,6 +121,15 @@ protected: virtual int measure(); virtual int collect(); + math::LowPassFilter2p _filter; + + /** + * Correct for 5V rail voltage variations + */ + void voltage_correction(float &diff_pres_pa, float &temperature); + + int _t_system_power; + struct system_power_s system_power; }; /* @@ -123,10 +137,12 @@ protected: */ extern "C" __EXPORT int meas_airspeed_main(int argc, char *argv[]); -MEASAirspeed::MEASAirspeed(int bus, int address, const char* path) : Airspeed(bus, address, - CONVERSION_INTERVAL, path) +MEASAirspeed::MEASAirspeed(int bus, int address, const char *path) : Airspeed(bus, address, + CONVERSION_INTERVAL, path), + _filter(MEAS_RATE, MEAS_DRIVER_FILTER_FREQ), + _t_system_power(-1) { - + memset(&system_power, 0, sizeof(system_power)); } int @@ -161,23 +177,25 @@ MEASAirspeed::collect() ret = transfer(nullptr, 0, &val[0], 4); if (ret < 0) { - perf_count(_comms_errors); - perf_end(_sample_perf); + perf_count(_comms_errors); + perf_end(_sample_perf); return ret; } - uint8_t status = val[0] & 0xC0; + uint8_t status = (val[0] & 0xC0) >> 6; - if (status == 2) { - log("err: stale data"); - perf_count(_comms_errors); - perf_end(_sample_perf); - return ret; - } else if (status == 3) { - log("err: fault"); - perf_count(_comms_errors); - perf_end(_sample_perf); - return ret; + switch (status) { + case 0: + break; + + case 1: + /* fallthrough */ + case 2: + /* fallthrough */ + case 3: + perf_count(_comms_errors); + perf_end(_sample_perf); + return -EAGAIN; } int16_t dp_raw = 0, dT_raw = 0; @@ -186,28 +204,67 @@ MEASAirspeed::collect() dp_raw = 0x3FFF & dp_raw; dT_raw = (val[2] << 8) + val[3]; dT_raw = (0xFFE0 & dT_raw) >> 5; - float temperature = ((200 * dT_raw) / 2047) - 50; + float temperature = ((200.0f * dT_raw) / 2047) - 50; - /* calculate differential pressure. As its centered around 8000 - * and can go positive or negative, enforce absolute value - */ + // Calculate differential pressure. As its centered around 8000 + // and can go positive or negative const float P_min = -1.0f; const float P_max = 1.0f; - float diff_press_pa = fabsf( ( ((float)dp_raw - 0.1f*16383.0f) * (P_max-P_min)/(0.8f*16383.0f) + P_min) * 6894.8f) - _diff_pres_offset; - if (diff_press_pa < 0.0f) - diff_press_pa = 0.0f; + const float PSI_to_Pa = 6894.757f; + /* + this equation is an inversion of the equation in the + pressure transfer function figure on page 4 of the datasheet + + We negate the result so that positive differential pressures + are generated when the bottom port is used as the static + port on the pitot and top port is used as the dynamic port + */ + float diff_press_PSI = -((dp_raw - 0.1f*16383) * (P_max-P_min)/(0.8f*16383) + P_min); + float diff_press_pa_raw = diff_press_PSI * PSI_to_Pa; + + // correct for 5V rail voltage if possible + voltage_correction(diff_press_pa_raw, temperature); + float diff_press_pa = fabsf(diff_press_pa_raw - _diff_pres_offset); + + /* + note that we return both the absolute value with offset + applied and a raw value without the offset applied. This + makes it possible for higher level code to detect if the + user has the tubes connected backwards, and also makes it + possible to correctly use offsets calculated by a higher + level airspeed driver. + + With the above calculation the MS4525 sensor will produce a + positive number when the top port is used as a dynamic port + and bottom port is used as the static port + + Also note that the _diff_pres_offset is applied before the + fabsf() not afterwards. It needs to be done this way to + prevent a bias at low speeds, but this also means that when + setting a offset you must set it based on the raw value, not + the offset value + */ + struct differential_pressure_s report; /* track maximum differential pressure measured (so we can work out top speed). */ if (diff_press_pa > _max_differential_pressure_pa) { - _max_differential_pressure_pa = diff_press_pa; + _max_differential_pressure_pa = diff_press_pa; } report.timestamp = hrt_absolute_time(); - report.error_count = perf_event_count(_comms_errors); + report.error_count = perf_event_count(_comms_errors); report.temperature = temperature; report.differential_pressure_pa = diff_press_pa; + report.differential_pressure_filtered_pa = _filter.apply(diff_press_pa); + + /* the dynamics of the filter can make it overshoot into the negative range */ + if (report.differential_pressure_filtered_pa < 0.0f) { + report.differential_pressure_filtered_pa = _filter.reset(diff_press_pa); + } + + report.differential_pressure_raw_pa = diff_press_pa_raw; report.voltage = 0; report.max_differential_pressure_pa = _max_differential_pressure_pa; @@ -231,13 +288,17 @@ MEASAirspeed::collect() void MEASAirspeed::cycle() { + int ret; + /* collection phase? */ if (_collect_phase) { /* perform collection */ - if (OK != collect()) { + ret = collect(); + if (OK != ret) { /* restart the measurement state machine */ start(); + _sensor_ok = false; return; } @@ -261,8 +322,12 @@ MEASAirspeed::cycle() } /* measurement phase */ - if (OK != measure()) - log("measure error"); + ret = measure(); + if (OK != ret) { + debug("measure error"); + } + + _sensor_ok = (ret == OK); /* next phase is collection */ _collect_phase = true; @@ -276,6 +341,62 @@ MEASAirspeed::cycle() } /** + correct for 5V rail voltage if the system_power ORB topic is + available + + See http://uav.tridgell.net/MS4525/MS4525-offset.png for a graph of + offset versus voltage for 3 sensors + */ +void +MEASAirspeed::voltage_correction(float &diff_press_pa, float &temperature) +{ +#ifdef CONFIG_ARCH_BOARD_PX4FMU_V2 + if (_t_system_power == -1) { + _t_system_power = orb_subscribe(ORB_ID(system_power)); + } + if (_t_system_power == -1) { + // not available + return; + } + bool updated = false; + orb_check(_t_system_power, &updated); + if (updated) { + orb_copy(ORB_ID(system_power), _t_system_power, &system_power); + } + if (system_power.voltage5V_v < 3.0f || system_power.voltage5V_v > 6.0f) { + // not valid, skip correction + return; + } + + const float slope = 65.0f; + /* + apply a piecewise linear correction, flattening at 0.5V from 5V + */ + float voltage_diff = system_power.voltage5V_v - 5.0f; + if (voltage_diff > 0.5f) { + voltage_diff = 0.5f; + } + if (voltage_diff < -0.5f) { + voltage_diff = -0.5f; + } + diff_press_pa -= voltage_diff * slope; + + /* + the temperature masurement varies as well + */ + const float temp_slope = 0.887f; + voltage_diff = system_power.voltage5V_v - 5.0f; + if (voltage_diff > 0.5f) { + voltage_diff = 0.5f; + } + if (voltage_diff < -1.0f) { + voltage_diff = -1.0f; + } + temperature -= voltage_diff * temp_slope; +#endif // CONFIG_ARCH_BOARD_PX4FMU_V2 +} + +/** * Local functions in support of the shell command. */ namespace meas_airspeed @@ -303,15 +424,17 @@ start(int i2c_bus) { int fd; - if (g_dev != nullptr) + if (g_dev != nullptr) { errx(1, "already started"); + } /* create the driver, try the MS4525DO first */ g_dev = new MEASAirspeed(i2c_bus, I2C_ADDRESS_MS4525DO, PATH_MS4525); /* check if the MS4525DO was instantiated */ - if (g_dev == nullptr) + if (g_dev == nullptr) { goto fail; + } /* try the MS5525DSO next if init fails */ if (OK != g_dev->Airspeed::init()) { @@ -319,22 +442,26 @@ start(int i2c_bus) g_dev = new MEASAirspeed(i2c_bus, I2C_ADDRESS_MS5525DSO, PATH_MS5525); /* check if the MS5525DSO was instantiated */ - if (g_dev == nullptr) + if (g_dev == nullptr) { goto fail; + } /* both versions failed if the init for the MS5525DSO fails, give up */ - if (OK != g_dev->Airspeed::init()) + if (OK != g_dev->Airspeed::init()) { goto fail; + } } /* set the poll rate to default, starts automatic data collection */ fd = open(AIRSPEED_DEVICE_PATH, O_RDONLY); - if (fd < 0) + if (fd < 0) { goto fail; + } - if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) + if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) { goto fail; + } exit(0); @@ -345,7 +472,7 @@ fail: g_dev = nullptr; } - errx(1, "driver start failed"); + errx(1, "no MS4525 airspeed sensor connected"); } /** @@ -379,21 +506,24 @@ test() int fd = open(AIRSPEED_DEVICE_PATH, O_RDONLY); - if (fd < 0) + if (fd < 0) { err(1, "%s open failed (try 'meas_airspeed start' if the driver is not running", AIRSPEED_DEVICE_PATH); + } /* do a simple demand read */ sz = read(fd, &report, sizeof(report)); - if (sz != sizeof(report)) + if (sz != sizeof(report)) { err(1, "immediate read failed"); + } warnx("single read"); - warnx("diff pressure: %8.4f pa", (double)report.differential_pressure_pa); + warnx("diff pressure: %d pa", (int)report.differential_pressure_pa); /* start the sensor polling at 2Hz */ - if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) + if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) { errx(1, "failed to set 2Hz poll rate"); + } /* read the sensor 5x and report each value */ for (unsigned i = 0; i < 5; i++) { @@ -404,23 +534,26 @@ test() fds.events = POLLIN; ret = poll(&fds, 1, 2000); - if (ret != 1) + if (ret != 1) { errx(1, "timed out waiting for sensor data"); + } /* now go get it */ sz = read(fd, &report, sizeof(report)); - if (sz != sizeof(report)) + if (sz != sizeof(report)) { err(1, "periodic read failed"); + } warnx("periodic read %u", i); - warnx("diff pressure: %8.4f pa", (double)report.differential_pressure_pa); + warnx("diff pressure: %d pa", (int)report.differential_pressure_pa); warnx("temperature: %d C (0x%02x)", (int)report.temperature, (unsigned) report.temperature); } /* reset the sensor polling to its default rate */ - if (OK != ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT)) + if (OK != ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT)) { errx(1, "failed to set default rate"); + } errx(0, "PASS"); } @@ -433,14 +566,17 @@ reset() { int fd = open(AIRSPEED_DEVICE_PATH, O_RDONLY); - if (fd < 0) + if (fd < 0) { err(1, "failed "); + } - if (ioctl(fd, SENSORIOCRESET, 0) < 0) + if (ioctl(fd, SENSORIOCRESET, 0) < 0) { err(1, "driver reset failed"); + } - if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) + if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) { err(1, "driver poll restart failed"); + } exit(0); } @@ -451,8 +587,9 @@ reset() void info() { - if (g_dev == nullptr) + if (g_dev == nullptr) { errx(1, "driver not running"); + } printf("state @ %p\n", g_dev); g_dev->print_info(); @@ -491,32 +628,37 @@ meas_airspeed_main(int argc, char *argv[]) /* * Start/load the driver. */ - if (!strcmp(argv[1], "start")) + if (!strcmp(argv[1], "start")) { meas_airspeed::start(i2c_bus); + } /* * Stop the driver */ - if (!strcmp(argv[1], "stop")) + if (!strcmp(argv[1], "stop")) { meas_airspeed::stop(); + } /* * Test the driver/device. */ - if (!strcmp(argv[1], "test")) + if (!strcmp(argv[1], "test")) { meas_airspeed::test(); + } /* * Reset the driver. */ - if (!strcmp(argv[1], "reset")) + if (!strcmp(argv[1], "reset")) { meas_airspeed::reset(); + } /* * Print driver information. */ - if (!strcmp(argv[1], "info") || !strcmp(argv[1], "status")) + if (!strcmp(argv[1], "info") || !strcmp(argv[1], "status")) { meas_airspeed::info(); + } meas_airspeed_usage(); exit(0); |