common: Add magnetometer online calibration.

Code for hard iron calibration: Every seconds (or faster if enough
samples), find a sphere that fit the compass data.

Based on Android code.

BRANCH=smaug
BUG=chrome-os-partner:39900
TEST=Check hard-iron bias is removed. Works better outside.

Change-Id: Iab479d5113b6560b4f01b0fd87373d2eecdb9b54
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/299583
Reviewed-by: Anton Staaf <robotboy@chromium.org>

5 files changed, 510 insertions, 0 deletions

diff --git a/common/build.mk b/common/build.mk
index cf2e1403a2..2a44c5124b 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -57,6 +57,7 @@ common-$(CONFIG_LID_ANGLE)+=motion_lid.o math_util.o
 common-$(CONFIG_LID_ANGLE_UPDATE)+=lid_angle.o
 common-$(CONFIG_LID_SWITCH)+=lid_switch.o
 common-$(CONFIG_LPC)+=acpi.o port80.o
+common-$(CONFIG_MAG_CALIBRATE)+= mag_cal.o math_util.o vec3.o mat33.o mat44.o
 common-$(CONFIG_MKBP_EVENT)+=mkbp_event.o
 common-$(CONFIG_ONEWIRE)+=onewire.o
 common-$(CONFIG_POWER_BUTTON)+=power_button.o
diff --git a/common/mag_cal.c b/common/mag_cal.c
new file mode 100644
index 0000000000..3ac2a7bcea
--- /dev/null
+++ b/common/mag_cal.c
@@ -0,0 +1,221 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "console.h"
+#include "mag_cal.h"
+#include "mat33.h"
+#include "mat44.h"
+
+#include "math.h"
+#include "math_util.h"
+#include "util.h"
+
+/* Data from sensor is in 16th of uT */
+#define MAG_CAL_RAW_UT      16
+
+#define MAX_EIGEN_RATIO     25.0f
+#define MAX_EIGEN_MAG       (80.0f * MAG_CAL_RAW_UT)
+#define MIN_EIGEN_MAG       (10.0f * MAG_CAL_RAW_UT)
+
+#define MAX_FIT_MAG         MAX_EIGEN_MAG
+#define MIN_FIT_MAG         MIN_EIGEN_MAG
+
+#define CPRINTF(format, args...) cprintf(CC_ACCEL, format, ## args)
+#define PRINTF_FLOAT(x)  ((int)((x) * 100.0f))
+
+/*
+ * eigen value magnitude and ratio test
+ *
+ * Using the magnetometer information, caculate the 3 eigen values/vectors
+ * for the transformation. Check the eigen values are sane.
+ */
+static int moc_eigen_test(struct mag_cal_t *moc)
+{
+	mat33_t S;
+	vec3_t eigenvals;
+	mat33_t eigenvecs;
+	float evmax, evmin, evmag;
+	int eigen_pass;
+
+	/* covariance matrix */
+	S[0][0] = moc->acc[0][0] - moc->acc[0][3] * moc->acc[0][3];
+	S[0][1] = S[1][0] = moc->acc[0][1] - moc->acc[0][3] * moc->acc[1][3];
+	S[0][2] = S[2][0] = moc->acc[0][2] - moc->acc[0][3] * moc->acc[2][3];
+	S[1][1] = moc->acc[1][1] - moc->acc[1][3] * moc->acc[1][3];
+	S[1][2] = S[2][1] = moc->acc[1][2] - moc->acc[1][3] * moc->acc[2][3];
+	S[2][2] = moc->acc[2][2] - moc->acc[2][3] * moc->acc[2][3];
+
+	mat33_get_eigenbasis(S, eigenvals, eigenvecs);
+
+	evmax = (eigenvals[X] > eigenvals[Y]) ? eigenvals[X] : eigenvals[Y];
+	evmax = (eigenvals[Z] > evmax) ? eigenvals[Z] : evmax;
+
+	evmin = (eigenvals[X] < eigenvals[Y]) ? eigenvals[X] : eigenvals[Y];
+	evmin = (eigenvals[Z] < evmin) ? eigenvals[Z] : evmin;
+
+	evmag = sqrtf(eigenvals[X] + eigenvals[Y] + eigenvals[Z]);
+
+	eigen_pass = (evmin * MAX_EIGEN_RATIO > evmax)
+		&& (evmag > MIN_EIGEN_MAG)
+		&& (evmag < MAX_EIGEN_MAG);
+
+#if 0
+	CPRINTF("mag eigenvalues: (%d %d %d), ",
+		PRINTF_FLOAT(eigenvals[X]),
+		PRINTF_FLOAT(eigenvals[Y]),
+		PRINTF_FLOAT(eigenvals[Z]));
+
+	CPRINTF("ratio %d, mag %d: pass %d\r\n",
+		PRINTF_FLOAT(evmax / evmin),
+		PRINTF_FLOAT(evmag),
+		PRINTF_FLOAT(eigen_pass));
+#endif
+
+	return eigen_pass;
+}
+
+/*
+ * Kasa sphere fitting with normal equation
+ */
+static int moc_fit(struct mag_cal_t *moc, vec3_t bias, float *radius)
+{
+	size4_t pivot;
+	vec4_t out;
+	int success = 0;
+
+	/*
+	 * To reduce stack size, moc->acc is A,
+	 * moc->acc_w is b: we are looking for out, where:
+	 *
+	 *    A    *   out   =    b
+	 * (4 x 4)   (4 x 1)   (4 x 1)
+	 */
+	/* complete the matrix: */
+	moc->acc[1][0] = moc->acc[0][1];
+	moc->acc[2][0] = moc->acc[0][2];
+	moc->acc[2][1] = moc->acc[1][2];
+	moc->acc[3][0] = moc->acc[0][3];
+	moc->acc[3][1] = moc->acc[1][3];
+	moc->acc[3][2] = moc->acc[2][3];
+	moc->acc[3][3] = 1.0f;
+
+	moc->acc_w[X] *= -1;
+	moc->acc_w[Y] *= -1;
+	moc->acc_w[Z] *= -1;
+	moc->acc_w[W] *= -1;
+
+	mat44_decompose_lup(moc->acc, pivot);
+
+	mat44_solve(moc->acc, out, moc->acc_w, pivot);
+
+	/*
+	 * spherei is defined by:
+	 * (x - xc)^2 + (y - yc)^2 + (z - zc)^2 = r^2
+	 *
+	 * Where r is:
+	 * xc = -out[X] / 2, yc = -out[Y] / 2, zc = -out[Z] / 2
+	 * r = sqrt(xc^2 + yc^2 + zc^2 - out[W])
+	 */
+
+	memcpy(bias, out, sizeof(vec3_t));
+	vec3_scalar_mul(bias, -0.5f);
+
+	*radius = sqrtf(vec3_dot(bias, bias) - out[W]);
+
+#if 0
+	CPRINTF("mag cal: bias (%d, %d, %d), R %d uT\n",
+		PRINTF_FLOAT(bias[X] / MAG_CAL_RAW_UT),
+		PRINTF_FLOAT(bias[Y] / MAG_CAL_RAW_UT),
+		PRINTF_FLOAT(bias[Z] / MAG_CAL_RAW_UT),
+		PRINTF_FLOAT(*radius / MAG_CAL_RAW_UT));
+#endif
+
+	/* TODO (menghsuan): bound on bias as well? */
+	if (*radius > MIN_FIT_MAG && *radius < MAX_FIT_MAG)
+		success = 1;
+
+	return success;
+}
+
+void init_mag_cal(struct mag_cal_t *moc)
+{
+	memset(moc->acc, 0, sizeof(moc->acc));
+	memset(moc->acc_w, 0, sizeof(moc->acc_w));
+	moc->nsamples = 0;
+}
+
+int mag_cal_update(struct mag_cal_t *moc, const vector_3_t v)
+{
+	int new_bias = 0;
+
+	/* 1. run accumulators */
+	float w = v[X] * v[X] + v[Y] * v[Y] + v[Z] * v[Z];
+
+	moc->acc[0][3] += v[X];
+	moc->acc[1][3] += v[Y];
+	moc->acc[2][3] += v[Z];
+	moc->acc_w[W] += w;
+
+	moc->acc[0][0] += v[X] * v[X];
+	moc->acc[0][1] += v[X] * v[Y];
+	moc->acc[0][2] += v[X] * v[Z];
+	moc->acc_w[X] += v[X] * w;
+
+	moc->acc[1][1] += v[Y] * v[Y];
+	moc->acc[1][2] += v[Y] * v[Z];
+	moc->acc_w[Y] += v[Y] * w;
+
+	moc->acc[2][2] += v[Z] * v[Z];
+	moc->acc_w[Z] += v[Z] * w;
+
+	if (moc->nsamples < MAG_CAL_MAX_SAMPLES)
+		moc->nsamples++;
+
+	/* 2. batch has enough samples? */
+	if (moc->batch_size > 0 && moc->nsamples >= moc->batch_size) {
+		float inv = 1.0f / moc->nsamples;
+
+		moc->acc[0][3] *= inv;
+		moc->acc[1][3] *= inv;
+		moc->acc[2][3] *= inv;
+		moc->acc_w[W] *= inv;
+
+		moc->acc[0][0] *= inv;
+		moc->acc[0][1] *= inv;
+		moc->acc[0][2] *= inv;
+		moc->acc_w[X] *= inv;
+
+		moc->acc[1][1] *= inv;
+		moc->acc[1][2] *= inv;
+		moc->acc_w[Y] *= inv;
+
+		moc->acc[2][2] *= inv;
+		moc->acc_w[Z] *= inv;
+
+		/* 3. eigen test */
+		if (moc_eigen_test(moc)) {
+			vec3_t bias;
+			float radius;
+
+			/* 4. Kasa sphere fitting */
+			if (moc_fit(moc, bias, &radius)) {
+
+				moc->bias[X] = bias[X] * -1;
+				moc->bias[Y] = bias[Y] * -1;
+				moc->bias[Z] = bias[Z] * -1;
+
+				moc->radius = radius;
+
+				new_bias = 1;
+			}
+		}
+		/* 5. reset for next batch */
+		init_mag_cal(moc);
+	}
+
+	return new_bias;
+}
+
diff --git a/common/mat33.c b/common/mat33.c
new file mode 100644
index 0000000000..8317ee8a97
--- /dev/null
+++ b/common/mat33.c
@@ -0,0 +1,170 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "mat33.h"
+#include "math.h"
+#include "util.h"
+
+#define K_EPSILON 1E-5f
+
+void init_zero_matrix(mat33_t A)
+{
+	memset(A, 0, sizeof(mat33_t));
+}
+
+void init_diagonal_matrix(mat33_t A, float x)
+{
+	size_t i;
+	init_zero_matrix(A);
+
+	for (i = 0; i < 3; ++i)
+		A[i][i] = x;
+}
+
+void mat33_scalar_mul(mat33_t A, float c)
+{
+	size_t i;
+	for (i = 0; i < 3; ++i) {
+		size_t j;
+		for (j = 0; j < 3; ++j)
+			A[i][j] *= c;
+	}
+}
+
+void mat33_swap_rows(mat33_t A, const size_t i, const size_t j)
+{
+	const size_t N = 3;
+	size_t k;
+
+	if (i == j)
+		return;
+
+	for (k = 0; k < N; ++k) {
+		float tmp = A[i][k];
+		A[i][k] = A[j][k];
+		A[j][k] = tmp;
+	}
+}
+
+/*
+ * Returns the eigenvalues and corresponding eigenvectors of the _symmetric_
+ * matrix.
+ * The i-th eigenvalue corresponds to the eigenvector in the i-th _row_ of
+ * "eigenvecs".
+ */
+void mat33_get_eigenbasis(mat33_t S, vec3_t e_vals, mat33_t e_vecs)
+{
+	const size_t N = 3;
+	size3_t ind;
+	size_t i, j, k, l, m;
+
+	for (k = 0; k < N; ++k) {
+		ind[k] = mat33_maxind(S, k);
+		e_vals[k] = S[k][k];
+	}
+
+	init_diagonal_matrix(e_vecs, 1.0f);
+
+	for (;;) {
+		float y, t, s, c, p, sum;
+		m = 0;
+		for (k = 1; k + 1 < N; ++k) {
+			if (fabsf(S[k][ind[k]]) >
+			    fabsf(S[m][ind[m]])) {
+				m = k;
+			}
+		}
+
+		k = m;
+		l = ind[m];
+		p = S[k][l];
+
+		if (fabsf(p) < K_EPSILON)
+			break;
+
+		y = (e_vals[l] - e_vals[k]) * 0.5f;
+
+		t = fabsf(y) + sqrtf(p * p + y * y);
+		s = sqrtf(p * p + t * t);
+		c = t / s;
+		s = p / s;
+		t = p * p / t;
+
+		if (y < 0.0f) {
+			s = -s;
+			t = -t;
+		}
+
+		S[k][l] = 0.0f;
+
+		e_vals[k] -= t;
+		e_vals[l] += t;
+
+		for (i = 0; i < k; ++i)
+			mat33_rotate(S, c, s, i, k, i, l);
+
+		for (i = k + 1; i < l; ++i)
+			mat33_rotate(S, c, s, k, i, i, l);
+
+		for (i = l + 1; i < N; ++i)
+			mat33_rotate(S, c, s, k, i, l, i);
+
+		for (i = 0; i < N; ++i) {
+			float tmp = c * e_vecs[k][i] - s * e_vecs[l][i];
+			e_vecs[l][i] = s * e_vecs[k][i] + c * e_vecs[l][i];
+			e_vecs[k][i] = tmp;
+		}
+
+		ind[k] = mat33_maxind(S, k);
+		ind[l] = mat33_maxind(S, l);
+
+		sum = 0.0f;
+		for (i = 0; i < N; ++i)
+			for (j = i + 1; j < N; ++j)
+				sum += fabsf(S[i][j]);
+
+		if (sum < K_EPSILON)
+			break;
+	}
+
+	for (k = 0; k < N; ++k) {
+		m = k;
+		for (l = k + 1; l < N; ++l)
+			if (e_vals[l] > e_vals[m])
+				m = l;
+
+		if (k != m) {
+			float tmp = e_vals[k];
+			e_vals[k] = e_vals[m];
+			e_vals[m] = tmp;
+
+			mat33_swap_rows(e_vecs, k, m);
+		}
+	}
+}
+
+/* index of largest off-diagonal element in row k */
+size_t mat33_maxind(mat33_t A, size_t k)
+{
+	const size_t N = 3;
+	size_t i, m = k + 1;
+
+	for (i = k + 2; i < N; ++i)
+		if (fabsf(A[k][i]) > fabsf(A[k][m]))
+			m = i;
+
+	return m;
+}
+
+void mat33_rotate(mat33_t A, float c, float s,
+		  size_t k, size_t l, size_t i, size_t j)
+{
+	float tmp = c * A[k][l] - s * A[i][j];
+	A[i][j] = s * A[k][l] + c * A[i][j];
+	A[k][l] = tmp;
+}
+
+
diff --git a/common/mat44.c b/common/mat44.c
new file mode 100644
index 0000000000..0f7f371461
--- /dev/null
+++ b/common/mat44.c
@@ -0,0 +1,85 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "mat44.h"
+#include "math.h"
+#include "util.h"
+
+#define K_EPSILON 1E-5f
+
+void mat44_decompose_lup(mat44_t LU, size4_t pivot)
+{
+	const size_t N = 4;
+	size_t i, j, k;
+
+	for (k = 0; k < N; ++k) {
+		float max = fabsf(LU[k][k]);
+		pivot[k] = k;
+		for (j = k + 1; j < N; ++j) {
+			if (max < fabsf(LU[j][k])) {
+				max = fabsf(LU[j][k]);
+				pivot[k] = j;
+			}
+		}
+
+		if (pivot[k] != k)
+			mat44_swap_rows(LU, k, pivot[k]);
+
+		if (fabsf(LU[k][k]) < K_EPSILON)
+			continue;
+
+		for (j = k + 1; j < N; ++j)
+			LU[k][j] /= LU[k][k];
+
+		for (i = k + 1; i < N; ++i)
+			for (j = k + 1; j < N; ++j)
+				LU[i][j] -= LU[i][k] * LU[k][j];
+	}
+}
+
+void mat44_swap_rows(mat44_t A, const size_t i, const size_t j)
+{
+	const size_t N = 4;
+	size_t k;
+
+	if (i == j)
+		return;
+
+	for (k = 0; k < N; ++k) {
+		float tmp = A[i][k];
+		A[i][k] = A[j][k];
+		A[j][k] = tmp;
+	}
+}
+
+void mat44_solve(mat44_t A, vec4_t x, const vec4_t b, const size4_t pivot)
+{
+	const size_t N = 4;
+	vec4_t b_copy;
+	size_t i, k;
+
+	memcpy(b_copy, b, sizeof(vec4_t));
+
+	for (k = 0; k < N; ++k) {
+		if (pivot[k] != k) {
+			float tmp = b_copy[k];
+			b_copy[k] = b_copy[pivot[k]];
+			b_copy[pivot[k]] = tmp;
+		}
+
+		x[k] = b_copy[k];
+		for (i = 0; i < k; ++i)
+			x[k] -= x[i] * A[k][i];
+		x[k] /= A[k][k];
+	}
+
+	for (k = N; k-- > 0;)
+		for (i = k + 1; i < N; ++i)
+			x[k] -= x[i] * A[k][i];
+}
+
+
+
diff --git a/common/vec3.c b/common/vec3.c
new file mode 100644
index 0000000000..12c33179c2
--- /dev/null
+++ b/common/vec3.c
@@ -0,0 +1,33 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "math.h"
+#include "math_util.h"
+#include "vec3.h"
+#include "util.h"
+
+void vec3_scalar_mul(vec3_t v, float c)
+{
+	v[X] *= c;
+	v[Y] *= c;
+	v[Z] *= c;
+}
+
+float vec3_dot(const vec3_t v, const vec3_t w)
+{
+	return v[X] * w[X] + v[Y] * w[Y] + v[Z] * w[Z];
+}
+
+float vec3_norm_squared(const vec3_t v)
+{
+	return vec3_dot(v, v);
+}
+
+float vec3_norm(const vec3_t v)
+{
+	return sqrtf(vec3_norm_squared(v));
+}
+