Fix output scaling for the hmc5883 driver. Add data checking, and fix an issue where the ORB topic could not be published due to being advertised in the wrong context.

apps/drivers/drv_mag.h

@@ -48,6 +48,8 @@
 /**
  * mag report structure.  Reads from the device must be in multiples of this
  * structure.
+ *
+ * Output values are in gauss.
  */
 struct mag_report {
 	float x;
@@ -99,4 +101,10 @@ ORB_DECLARE(sensor_mag);
 /** set the mag scaling constants to the structure pointed to by (arg) */
 #define MAGIOCSSCALE		_MAGIOC(5)
 
+/** copy the mag scaling constants to the structure pointed to by (arg) */
+#define MAGIOCGSCALE		_MAGIOC(6)
+
+/** perform self-calibration, update scale factors to canonical units */
+#define MAGIOCCALIBRATE		_MAGIOC(7)
+
 #endif /* _DRV_MAG_H */

apps/drivers/hmc5883/hmc5883.cpp

@@ -43,6 +43,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <stdbool.h>
 #include <semaphore.h>
 #include <string.h>
@@ -63,7 +64,6 @@
 
 #include <drivers/drv_mag.h>
 
-
 /*
  * HMC5883 internal constants and data structures.
  */
@@ -137,14 +137,14 @@ protected:
 	virtual int		probe();
 
 private:
-	struct work_s		_work;
+	work_s			_work;
 	unsigned		_measure_ticks;
 
 	unsigned		_num_reports;
 	volatile unsigned	_next_report;
 	volatile unsigned	_oldest_report;
-	struct mag_report	*_reports;
-
+	mag_report		*_reports;
+	mag_scale		_scale;
 	bool			_collect_phase;
 
 	int			_mag_topic;
@@ -257,6 +257,7 @@ HMC5883::HMC5883(int bus) :
 	_next_report(0),
 	_oldest_report(0),
 	_reports(nullptr),
+	_mag_topic(-1),
 	_reads(0),
 	_measure_errors(0),
 	_read_errors(0),
@@ -266,6 +267,14 @@ HMC5883::HMC5883(int bus) :
 	// enable debug() calls
 	_debug_enabled = true;
 
+	// default scaling
+	_scale.x_offset = 0;
+	_scale.x_scale = 1.0f / 1090.0f;	/* default range scale from counts to gauss */
+	_scale.y_offset = 0;
+	_scale.y_scale = 1.0f / 1090.0f;	/* default range scale from counts to gauss */
+	_scale.z_offset = 0;
+	_scale.z_scale = 1.0f / 1090.0f;	/* default range scale from counts to gauss */
+
 	// work_cancel in the dtor will explode if we don't do this...
 	_work.worker = nullptr;
 }
@@ -290,18 +299,6 @@ HMC5883::init()
 	if (ret != OK)
 		goto out;
 
-	/* assuming we're good, advertise the object */
-	struct mag_report m;
-
-	/* if this fails (e.g. no object in the system) that's OK */
-	memset(&m, 0, sizeof(m));
-	_mag_topic = orb_advertise(ORB_ID(sensor_mag), &m);
-
-	if (_mag_topic < 0) {
-		debug("failed to create sensor_baro object");
-	} else {
-		ret = 0;
-	}
 out:
 	return ret;
 }
@@ -340,7 +337,6 @@ HMC5883::close_last(struct file *filp)
 int
 HMC5883::probe()
 {
-	uint8_t	cmd[] = { ADDR_STATUS };
 	uint8_t data[3];
 
 	if (read_reg(ADDR_ID_A, data[0]) ||
@@ -434,7 +430,7 @@ HMC5883::ioctl(struct file *filp, int cmd, unsigned long arg)
 				_measure_ticks = 0;
 				return OK;
 
-				/* external signalling not supported */
+				/* external signalling (DRDY) not supported */
 			case MAG_POLLRATE_EXTERNAL:
 
 				/* zero would be bad */
@@ -486,7 +482,30 @@ HMC5883::ioctl(struct file *filp, int cmd, unsigned long arg)
 			return OK;
 		}
 
+	case MAGIOCSSCALE:
+		/* set new scale factors */
+		memcpy(&_scale, (mag_scale *)arg, sizeof(_scale));
+		return 0;
+
+	case MAGIOCGSCALE:
+		/* copy out scale factors */
+		memcpy((mag_scale *)arg, &_scale, sizeof(_scale));
+		return 0;
+
+	case MAGIOCCALIBRATE:
+		/* XXX perform auto-calibration */
+		return -EINVAL;
+
+	case MAGIOCSSAMPLERATE:
+		/* not supported, always 1 sample per poll */
+		return -EINVAL;
+
+	case MAGIOCSLOWPASS:
+		/* not supported, no internal filtering */
+		return -EINVAL;
+
 	case MAGIOCSREPORTFORMAT:
+		/* not supported, no custom report format */
 		return -EINVAL;
 
 	default:
@@ -526,6 +545,25 @@ HMC5883::cycle_trampoline(void *arg)
 void
 HMC5883::cycle()
 {
+	/* 
+	 * We have to publish the mag topic in the context of the workq 
+	 * in order to ensure that the descriptor is valid when we go to publish.
+	 *
+	 * @bug	We can't really ever be torn down and restarted, since this
+	 *      descriptor will never be closed and on the restart we will be
+	 *      unable to re-advertise.
+	 */
+	if (_mag_topic == -1) {
+		struct mag_report m;
+
+		/* if this fails (e.g. no object in the system) we will cope */
+		memset(&m, 0, sizeof(m));
+		_mag_topic = orb_advertise(ORB_ID(sensor_mag), &m);
+
+		if (_mag_topic < 0)
+			debug("failed to create sensor_mag object");
+	}
+
 	/* collection phase? */
 	if (_collect_phase) {
 
@@ -591,33 +629,55 @@ HMC5883::collect()
 #pragma pack(push, 1)
 	struct { /* status register and data as read back from the device */
 		uint8_t		x[2];
-		uint8_t		z[2];
 		uint8_t		y[2];
-		uint8_t		status;
+		uint8_t		z[2];
 	}	hmc_report;
 #pragma pack(pop)
+	struct {
+		int16_t		x, y, z;
+	} report;
 	int	ret = -EIO;
-	uint8_t	cmd[1];
+	uint8_t	cmd;
+
 
 	perf_begin(_sample_perf);
 
 	/* this should be fairly close to the end of the measurement, so the best approximation of the time */
 	_reports[_next_report].timestamp = hrt_absolute_time();
 
+	/*
+	 * @note  We could read the status register here, which could tell us that
+	 *        we were too early and that the output registers are still being
+	 *        written.  In the common case that would just slow us down, and 
+	 *        we're better off just never being early.
+	 */
+
 	/* get measurements from the device */
-	cmd[0] = ADDR_DATA_OUT_X_MSB;
-	ret = transfer(&cmd[0], 1, &hmc_report.x[0], sizeof(hmc_report));
+	cmd = ADDR_DATA_OUT_X_MSB;
+	ret = transfer(&cmd, 1, (uint8_t *)&hmc_report, sizeof(hmc_report));
 	if (ret != OK) {
 		debug("data/status read error");
 		goto out;
 	}
 
-	/* XXX check status? */
+	/* swap the data we just received */
+	report.x = ((int16_t)hmc_report.x[0] << 8) + hmc_report.x[1];
+	report.y = ((int16_t)hmc_report.y[0] << 8) + hmc_report.y[1];
+	report.z = ((int16_t)hmc_report.z[0] << 8) + hmc_report.z[1];
+
+	/* 
+	 * If any of the values are -4096, there was an internal math error in the sensor. 
+	 * Generalise this to a simple range check that will also catch some bit errors.
+	 */
+	if ((abs(report.x) > 2048) ||
+	    (abs(report.y) > 2048) ||
+	    (abs(report.z) > 2048))
+		goto out;
 
-	/* XXX scaling */
-	_reports[_next_report].x = meas_to_float(hmc_report.x);
-	_reports[_next_report].y = meas_to_float(hmc_report.y);
-	_reports[_next_report].z = meas_to_float(hmc_report.z);
+	/* scale values for output */
+	_reports[_next_report].x = report.x * _scale.x_scale + _scale.x_offset;
+	_reports[_next_report].y = report.y * _scale.y_scale + _scale.y_offset;
+	_reports[_next_report].z = report.z * _scale.z_scale + _scale.z_offset;
 
 	/* publish it */
 	orb_publish(ORB_ID(sensor_mag), _mag_topic, &_reports[_next_report]);