altos: Calibrate IMU accelerometers too

Average the IMU accelerometer values pointing up and down so that we
have a zero-g offset for all three axes. This can then be used to
compute which direction the rocket is pointing while sitting on the pad.

Signed-off-by: Keith Packard <keithp@keithp.com>

4 files changed, 83 insertions, 10 deletions

diff --git a/src/core/ao.h b/src/core/ao.h
index ea37885e..d12f13a0 100644
--- a/src/core/ao.h
+++ b/src/core/ao.h
@@ -739,7 +739,7 @@ extern __xdata uint8_t ao_force_freq;
 #endif
 
 #define AO_CONFIG_MAJOR	1
-#define AO_CONFIG_MINOR	14
+#define AO_CONFIG_MINOR	15
 
 #define AO_AES_LEN 16
 
@@ -773,6 +773,11 @@ struct ao_config {
 #if HAS_RADIO_AMP
 	uint8_t		radio_amp;		/* minor version 14 */
 #endif
+#if HAS_GYRO
+	uint16_t	accel_zero_along;	/* minor version 15 */
+	uint16_t	accel_zero_across;	/* minor version 15 */
+	uint16_t	accel_zero_through;	/* minor version 15 */
+#endif
 };
 
 #define AO_IGNITE_MODE_DUAL		0
diff --git a/src/core/ao_config.c b/src/core/ao_config.c
index b480e14c..82faf32b 100644
--- a/src/core/ao_config.c
+++ b/src/core/ao_config.c
@@ -156,6 +156,19 @@ _ao_config_get(void)
 		if (minor  < 14)
 			ao_config.radio_amp = AO_CONFIG_DEFAULT_RADIO_AMP;
 #endif
+#if HAS_GYRO
+		if (minor < 15) {
+			ao_config.accel_zero_along = 0;
+			ao_config.accel_zero_across = 0;
+			ao_config.accel_zero_through = 0;
+
+			/* Reset the main accel offsets to force
+			 * re-calibration
+			 */
+			ao_config.accel_plus_g = 0;
+			ao_config.accel_minus_g = 0;
+		}
+#endif
 		ao_config.minor = AO_CONFIG_MINOR;
 		ao_config_dirty = 1;
 	}
@@ -275,17 +288,34 @@ ao_config_accel_calibrate_show(void) __reentrant
 {
 	printf("Accel cal +1g: %d -1g: %d\n",
 	       ao_config.accel_plus_g, ao_config.accel_minus_g);
+#if HAS_GYRO
+	printf ("IMU cal along %d across %d through %d\n",
+		ao_config.accel_zero_along,
+		ao_config.accel_zero_across,
+		ao_config.accel_zero_through);
+#endif
 }
 
 #define ACCEL_CALIBRATE_SAMPLES	1024
 #define ACCEL_CALIBRATE_SHIFT	10
 
+#if HAS_GYRO
+static int16_t accel_cal_along;
+static int16_t accel_cal_across;
+static int16_t accel_cal_through;
+#endif
+
 static int16_t
 ao_config_accel_calibrate_auto(char *orientation) __reentrant
 {
 	uint16_t	i;
 	int32_t		accel_total;
 	uint8_t		cal_data_ring;
+#if HAS_GYRO
+	int32_t		accel_along_total = 0;
+	int32_t		accel_across_total = 0;
+	int32_t		accel_through_total = 0;
+#endif
 
 	printf("Orient antenna %s and press a key...", orientation);
 	flush();
@@ -299,10 +329,20 @@ ao_config_accel_calibrate_auto(char *orientation) __reentrant
 		ao_sleep(DATA_TO_XDATA(&ao_sample_data));
 		while (i && cal_data_ring != ao_sample_data) {
 			accel_total += (int32_t) ao_data_accel(&ao_data_ring[cal_data_ring]);
+#if HAS_GYRO
+			accel_along_total += (int32_t) ao_data_along(&ao_data_ring[cal_data_ring]);
+			accel_across_total += (int32_t) ao_data_across(&ao_data_ring[cal_data_ring]);
+			accel_through_total += (int32_t) ao_data_through(&ao_data_ring[cal_data_ring]);
+#endif
 			cal_data_ring = ao_data_ring_next(cal_data_ring);
 			i--;
 		}
 	}
+#if HAS_GYRO
+	accel_cal_along = accel_along_total >> ACCEL_CALIBRATE_SHIFT;
+	accel_cal_across = accel_across_total >> ACCEL_CALIBRATE_SHIFT;
+	accel_cal_through = accel_through_total >> ACCEL_CALIBRATE_SHIFT;
+#endif
 	return accel_total >> ACCEL_CALIBRATE_SHIFT;
 }
 
@@ -310,12 +350,28 @@ void
 ao_config_accel_calibrate_set(void) __reentrant
 {
 	int16_t	up, down;
+#if HAS_GYRO
+	int16_t	accel_along_up, accel_along_down;
+	int16_t	accel_across_up, accel_across_down;
+	int16_t	accel_through_up, accel_through_down;
+#endif
+	
 	ao_cmd_decimal();
 	if (ao_cmd_status != ao_cmd_success)
 		return;
 	if (ao_cmd_lex_i == 0) {
 		up = ao_config_accel_calibrate_auto("up");
+#if HAS_GYRO
+		accel_along_up = accel_cal_along;
+		accel_across_up = accel_cal_across;
+		accel_through_up = accel_cal_through;
+#endif
 		down = ao_config_accel_calibrate_auto("down");
+#if HAS_GYRO
+		accel_along_down = accel_cal_along;
+		accel_across_down = accel_cal_across;
+		accel_through_down = accel_cal_through;
+#endif
 	} else {
 		up = ao_cmd_lex_i;
 		ao_cmd_decimal();
@@ -331,6 +387,11 @@ ao_config_accel_calibrate_set(void) __reentrant
 	_ao_config_edit_start();
 	ao_config.accel_plus_g = up;
 	ao_config.accel_minus_g = down;
+#if HAS_GYRO
+	ao_config.accel_zero_along = (accel_along_up + accel_along_down) / 2;
+	ao_config.accel_zero_across = (accel_across_up + accel_across_down) / 2;
+	ao_config.accel_zero_through = (accel_through_up + accel_through_down) / 2;
+#endif
 	_ao_config_edit_finish();
 }
 #endif /* HAS_ACCEL */
diff --git a/src/core/ao_sample.c b/src/core/ao_sample.c
index 676e0ffd..a9d50cb2 100644
--- a/src/core/ao_sample.c
+++ b/src/core/ao_sample.c
@@ -139,19 +139,16 @@ ao_sample_preflight_set(void)
 	/* No rotation yet */
 	ao_quaternion_init_zero_rotation(&ao_rotation);
 
-	/* XXX Assume we're pointing straight up for now */
+	/* Take the pad IMU acceleration values and compute our current direction
+	 */
 	ao_quaternion_init_vector(&ao_pad_orientation,
-				  ao_ground_accel_across,
-				  ao_ground_accel_through,
-				  -ao_ground_accel_along);
+				  ao_ground_accel_across - ao_config.accel_zero_across,
+				  ao_ground_accel_through - ao_config.accel_zero_through,
+				  -ao_ground_accel_along - ao_config.accel_zero_along);
+
 	ao_quaternion_normalize(&ao_pad_orientation,
 				&ao_pad_orientation);
 				  
-	printf ("pad r%8.5f x%8.5f y%8.5f z%8.5f\n",
-		ao_pad_orientation.r,
-		ao_pad_orientation.x,
-		ao_pad_orientation.y,
-		ao_pad_orientation.z);
 #endif	
 	nsamples = 0;
 }
diff --git a/src/test/ao_flight_test.c b/src/test/ao_flight_test.c
index e2f63e34..7f18c80e 100644
--- a/src/test/ao_flight_test.c
+++ b/src/test/ao_flight_test.c
@@ -234,6 +234,9 @@ struct ao_config {
 	uint16_t	apogee_lockout;
 #if TELEMEGA
 	struct ao_pyro	pyro[AO_PYRO_NUM];	/* minor version 12 */
+	int16_t		accel_zero_along;
+	int16_t		accel_zero_across;
+	int16_t		accel_zero_through;
 #endif
 };
 
@@ -719,6 +722,13 @@ ao_sleep(void *wchan)
 			} else if (nword >= 6 && strcmp(words[0], "Accel") == 0) {
 				ao_config.accel_plus_g = atoi(words[3]);
 				ao_config.accel_minus_g = atoi(words[5]);
+#ifdef TELEMEGA
+			} else if (nword >= 8 && strcmp(words[0], "IMU") == 0) {
+				ao_config.accel_zero_along = atoi(words[3]);
+				ao_config.accel_zero_across = atoi(words[5]);
+				ao_config.accel_zero_through = atoi(words[7]);
+				printf ("%d %d %d\n", ao_config.accel_zero_along, ao_config.accel_zero_across, ao_config.accel_zero_through);
+#endif
 			} else if (nword >= 4 && strcmp(words[0], "Main") == 0) {
 				ao_config.main_deploy = atoi(words[2]);
 			} else if (nword >= 3 && strcmp(words[0], "Apogee") == 0 &&