1 files changed, 40 insertions, 5 deletions

diff --git a/apps/plugins/lib/fixedpoint.h b/apps/plugins/lib/fixedpoint.h
index dfabbad8dc..ef50dd0085 100644
--- a/apps/plugins/lib/fixedpoint.h
+++ b/apps/plugins/lib/fixedpoint.h
@@ -21,11 +21,44 @@
  *
  ****************************************************************************/
 
-long fsincos(unsigned long phase, long *cos);
-long fsqrt(long a, unsigned int fracbits);
-long cos_int(int val);
-long sin_int(int val);
-long flog(int x);
+/** PLUGINS - FIXED POINT MATH ROUTINES - USAGE
+ *
+ *  - x and y arguments are fixed point integers
+ *  - fracbits is the number of fractional bits in the argument(s)
+ *  - functions return long fixed point integers with the specified number
+ *    of fractional bits unless otherwise specified
+ *
+ *  Calculate sin and cos of an angle:
+ *      fp_sincos(phase, *cos)
+ *          where phase is a 32 bit unsigned integer with 0 representing 0
+ *          and 0xFFFFFFFF representing 2*pi, and *cos is the address to
+ *          a long signed integer.  Value returned is a long signed integer
+ *          from LONG_MIN to LONG_MAX, representing -1 to 1 respectively.
+ *          That is, value is a fixed point integer with 31 fractional bits.
+ *
+ *  Take square root of a fixed point number:
+ *      fp_sqrt(x, fracbits)
+ *
+ *  Calculate sin or cos of an angle (very fast, from a table):
+ *      fp14_sin(angle)
+ *      fp14_cos(angle)
+ *          where angle is a non-fixed point integer in degrees.  Value
+ *          returned is a fixed point integer with 14 fractional bits.
+ *
+ *  Calculate the natural log of a positive fixed point integer
+ *      fp16_log(x)
+ *          where x and the value returned are fixed point integers
+ *          with 16 fractional bits.
+ */
+
+#ifndef _FIXEDPOINT_H_PLUGINS
+#define _FIXEDPOINT_H_PLUGINS
+
+long fp_sincos(unsigned long phase, long *cos);
+long fp_sqrt(long a, unsigned int fracbits);
+long fp14_cos(int val);
+long fp14_sin(int val);
+long fp16_log(int x);
 
 /* fast unsigned multiplication (16x16bit->32bit or 32x32bit->32bit,
  * whichever is faster for the architecture) */
@@ -34,3 +67,5 @@ long flog(int x);
 #else /* SH1, coldfire */
 #define FMULU(a, b) ((uint32_t) (((uint16_t) (a)) * ((uint16_t) (b))))
 #endif
+
+#endif