diff --git a/sw/airborne/math/pprz_algebra_double.h b/sw/airborne/math/pprz_algebra_double.h
index dec0c22006..5b7c8752ec 100644
--- a/sw/airborne/math/pprz_algebra_double.h
+++ b/sw/airborne/math/pprz_algebra_double.h
@@ -136,6 +136,18 @@ static inline void double_quat_normalize(struct DoubleQuat* q)
   }
 }
 
+/** Rotation matrix from 321 Euler angles (double).
+ * The Euler angles are interpreted as zy'x'' (intrinsic) rotation.
+ * First rotate around z with psi, then around the new y' with theta,
+ * then around new x'' with phi.
+ * This is the same as a xyz (extrinsic) rotation,
+ * rotating around the fixed x, then y then z axis.
+ * - psi range: -pi < psi <= pi
+ * - theta range: -pi/2 <= theta <= pi/2
+ * - phi range: -pi < phi <= pi
+ * @param[out] rm pointer to rotation matrix
+ * @param[in]  e pointer to Euler angles
+ */
 extern void double_rmat_of_eulers_321(struct DoubleRMat* rm, struct DoubleEulers* e);
 extern void double_quat_of_eulers(struct DoubleQuat* q, struct DoubleEulers* e);
 extern void double_eulers_of_quat(struct DoubleEulers* e, struct DoubleQuat* q);
diff --git a/sw/airborne/math/pprz_algebra_float.h b/sw/airborne/math/pprz_algebra_float.h
index 11a1a60318..1728064e99 100644
--- a/sw/airborne/math/pprz_algebra_float.h
+++ b/sw/airborne/math/pprz_algebra_float.h
@@ -285,6 +285,18 @@ extern void float_rmat_transp_ratemult(struct FloatRates* rb, struct FloatRMat*
 /** initialises a rotation matrix from unit vector axis and angle */
 extern void float_rmat_of_axis_angle(struct FloatRMat* rm, struct FloatVect3* uv, float angle);
 
+/** Rotation matrix from 321 Euler angles (float).
+ * The Euler angles are interpreted as zy'x'' (intrinsic) rotation.
+ * First rotate around z with psi, then around the new y' with theta,
+ * then around new x'' with phi.
+ * This is the same as a xyz (extrinsic) rotation,
+ * rotating around the fixed x, then y then z axis.
+ * - psi range: -pi < psi <= pi
+ * - theta range: -pi/2 <= theta <= pi/2
+ * - phi range: -pi < phi <= pi
+ * @param[out] rm pointer to rotation matrix
+ * @param[in]  e pointer to Euler angles
+ */
 extern void float_rmat_of_eulers_321(struct FloatRMat* rm, struct FloatEulers* e);
 extern void float_rmat_of_eulers_312(struct FloatRMat* rm, struct FloatEulers* e);
 #define float_rmat_of_eulers float_rmat_of_eulers_321
diff --git a/sw/airborne/math/pprz_algebra_int.h b/sw/airborne/math/pprz_algebra_int.h
index 6c21786756..837ac2b73e 100644
--- a/sw/airborne/math/pprz_algebra_int.h
+++ b/sw/airborne/math/pprz_algebra_int.h
@@ -382,7 +382,18 @@ extern void int32_rmat_transp_ratemult(struct Int32Rates* rb, struct Int32RMat*
 /// Convert unit quaternion to rotation matrix.
 extern void int32_rmat_of_quat(struct Int32RMat* rm, struct Int32Quat* q);
 
-/// Rotation matrix from 321 Euler angles.
+/** Rotation matrix from 321 Euler angles (int).
+ * The Euler angles are interpreted as zy'x'' (intrinsic) rotation.
+ * First rotate around z with psi, then around the new y' with theta,
+ * then around new x'' with phi.
+ * This is the same as a xyz (extrinsic) rotation,
+ * rotating around the fixed x, then y then z axis.
+ * - psi range: -pi < psi <= pi
+ * - theta range: -pi/2 <= theta <= pi/2
+ * - phi range: -pi < phi <= pi
+ * @param[out] rm pointer to rotation matrix
+ * @param[in]  e pointer to Euler angles
+ */
 extern void int32_rmat_of_eulers_321(struct Int32RMat* rm, struct Int32Eulers* e);
 
 /// Rotation matrix from 312 Euler angles.