1 files changed, 89 insertions, 0 deletions
diff --git a/apps/systemlib/conversions.c b/apps/systemlib/conversions.c
index 9105d83cb..32df446d9 100644
--- a/apps/systemlib/conversions.c
+++ b/apps/systemlib/conversions.c
@@ -55,3 +55,92 @@ int16_t_from_bytes(uint8_t bytes[])
 
 	return u.w;
 }
+
+void rot2quat(const float R[9], float Q[4])
+{
+  float q0_2;
+  float q1_2;
+  float q2_2;
+  float q3_2;
+  int32_t idx;
+
+  /* conversion of rotation matrix to quaternion
+   * choose the largest component to begin with */
+  q0_2 = (((1.0F + R[0]) + R[4]) + R[8]) / 4.0F;
+  q1_2 = (((1.0F + R[0]) - R[4]) - R[8]) / 4.0F;
+  q2_2 = (((1.0F - R[0]) + R[4]) - R[8]) / 4.0F;
+  q3_2 = (((1.0F - R[0]) - R[4]) + R[8]) / 4.0F;
+
+  idx = 0;
+
+  if (q0_2 < q1_2) {
+    q0_2 = q1_2;
+
+    idx = 1;
+  }
+
+  if (q0_2 < q2_2) {
+    q0_2 = q2_2;
+    idx = 2;
+  }
+
+  if (q0_2 < q3_2) {
+    q0_2 = q3_2;
+    idx = 3;
+  }
+
+  q0_2 = sqrtf(q0_2);
+
+  /* solve for the remaining three components */
+  if (idx == 0) {
+    q1_2 = q0_2;
+    q2_2 = (R[5] - R[7]) / 4.0F / q0_2;
+    q3_2 = (R[6] - R[2]) / 4.0F / q0_2;
+    q0_2 = (R[1] - R[3]) / 4.0F / q0_2;
+  } else if (idx == 1) {
+    q2_2 = q0_2;
+    q1_2 = (R[5] - R[7]) / 4.0F / q0_2;
+    q3_2 = (R[3] + R[1]) / 4.0F / q0_2;
+    q0_2 = (R[6] + R[2]) / 4.0F / q0_2;
+  } else if (idx == 2) {
+    q3_2 = q0_2;
+    q1_2 = (R[6] - R[2]) / 4.0F / q0_2;
+    q2_2 = (R[3] + R[1]) / 4.0F / q0_2;
+    q0_2 = (R[7] + R[5]) / 4.0F / q0_2;
+  } else {
+    q1_2 = (R[1] - R[3]) / 4.0F / q0_2;
+    q2_2 = (R[6] + R[2]) / 4.0F / q0_2;
+    q3_2 = (R[7] + R[5]) / 4.0F / q0_2;
+  }
+
+  /* return values */
+  Q[0] = q1_2;
+  Q[1] = q2_2;
+  Q[2] = q3_2;
+  Q[3] = q0_2;
+}
+
+void quat2rot(const float Q[4], float R[9])
+{
+  float q0_2;
+  float q1_2;
+  float q2_2;
+  float q3_2;
+
+  memset(&R[0], 0, 9U * sizeof(float));
+
+  q0_2 = Q[0] * Q[0];
+  q1_2 = Q[1] * Q[1];
+  q2_2 = Q[2] * Q[2];
+  q3_2 = Q[3] * Q[3];
+
+  R[0] = ((q0_2 + q1_2) - q2_2) - q3_2;
+  R[3] = 2.0F * (Q[1] * Q[2] - Q[0] * Q[3]);
+  R[6] = 2.0F * (Q[1] * Q[3] + Q[0] * Q[2]);
+  R[1] = 2.0F * (Q[1] * Q[2] + Q[0] * Q[3]);
+  R[4] = ((q0_2 + q2_2) - q1_2) - q3_2;
+  R[7] = 2.0F * (Q[2] * Q[3] - Q[0] * Q[1]);
+  R[2] = 2.0F * (Q[1] * Q[3] - Q[0] * Q[2]);
+  R[5] = 2.0F * (Q[2] * Q[3] + Q[0] * Q[1]);
+  R[8] = ((q0_2 + q3_2) - q1_2) - q2_2;
+}
+\ No newline at end of file