From befc6b7b9be2fdc4de1f0756f4d257ac0dd44503 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Wed, 16 Jan 2013 09:15:22 +1100
Subject: [PATCH] Filter: fixed butter filter build on px4

---
 libraries/Filter/Butter.h | 56 ++++++++++++++++++++-------------------
 1 file changed, 29 insertions(+), 27 deletions(-)

diff --git a/libraries/Filter/Butter.h b/libraries/Filter/Butter.h
index face55fcd1..b72938aa6c 100644
--- a/libraries/Filter/Butter.h
+++ b/libraries/Filter/Butter.h
@@ -2,6 +2,8 @@
 #ifndef __FILTER_BUTTER_H__
 #define __FILTER_BUTTER_H__
 
+#include <AP_HAL.h>
+
 template <typename Coefficients>
 class Butter2
 {
@@ -19,9 +21,9 @@ private:
 
 struct butter100_025_coeffs
 {
-  static const float A1 = 1.9777864838;
-  static const float A2 = -0.9780305085;
-  static const float GAIN = 1.639178228e+04;
+  static constexpr float A1 = 1.9777864838;
+  static constexpr float A2 = -0.9780305085;
+  static constexpr float GAIN = 1.639178228e+04;
 };
 typedef Butter2<butter100_025_coeffs> butter100hz0_25; //100hz sample, 0.25hz fcut
 typedef Butter2<butter100_025_coeffs> butter50hz0_125; //50hz sample, 0.125hz fcut
@@ -29,9 +31,9 @@ typedef Butter2<butter100_025_coeffs> butter10hz0_025; //10hz sample, 0.025hz fc
 
 struct butter100_05_coeffs
 {
-  static const float A1 = 1.9555782403;
-  static const float A2 = -0.9565436765;
-  static const float GAIN = 4.143204922e+03;
+  static constexpr float A1 = 1.9555782403;
+  static constexpr float A2 = -0.9565436765;
+  static constexpr float GAIN = 4.143204922e+03;
 };
 typedef Butter2<butter100_05_coeffs> butter100hz0_5; //100hz sample, 0.5hz fcut
 typedef Butter2<butter100_05_coeffs> butter50hz0_25; //50hz sample, 0.25hz fcut
@@ -39,9 +41,9 @@ typedef Butter2<butter100_05_coeffs> butter10hz0_05; //10hz sample, 0.05hz fcut
 
 struct butter100_1_coeffs
 {
-  static const float A1 = 1.9111970674;
-  static const float A2 = -0.9149758348;
-  static const float GAIN = 1.058546241e+03;
+  static constexpr float A1 = 1.9111970674;
+  static constexpr float A2 = -0.9149758348;
+  static constexpr float GAIN = 1.058546241e+03;
 };
 typedef Butter2<butter100_1_coeffs> butter100hz1_0; //100hz sample, 1hz fcut
 typedef Butter2<butter100_1_coeffs> butter50hz0_5; //50hz sample, 0.5hz fcut
@@ -49,9 +51,9 @@ typedef Butter2<butter100_1_coeffs> butter10hz0_1; //10hz sample, 0.1hz fcut
 
 struct butter100_1_5_coeffs
 {
-  static const float A1 = 1.8668922797;
-  static const float A2 = -0.8752145483;
-  static const float GAIN = 4.806381793e+02;
+  static constexpr float A1 = 1.8668922797;
+  static constexpr float A2 = -0.8752145483;
+  static constexpr float GAIN = 4.806381793e+02;
 };
 typedef Butter2<butter100_1_5_coeffs> butter100hz1_5; //100hz sample, 1.5hz fcut
 typedef Butter2<butter100_1_5_coeffs> butter50hz0_75; //50hz sample, 0.75hz fcut
@@ -59,9 +61,9 @@ typedef Butter2<butter100_1_5_coeffs> butter10hz0_15; //10hz sample, 0.15hz fcut
 
 struct butter100_2_coeffs
 {
-  static const float A1 = 1.8226949252;
-  static const float A2 = -0.8371816513;
-  static const float GAIN = 2.761148367e+02;
+  static constexpr float A1 = 1.8226949252;
+  static constexpr float A2 = -0.8371816513;
+  static constexpr float GAIN = 2.761148367e+02;
 };
 typedef Butter2<butter100_2_coeffs> butter100hz2_0; //100hz sample, 2hz fcut
 typedef Butter2<butter100_2_coeffs> butter50hz1_0; //50hz sample, 1hz fcut
@@ -69,9 +71,9 @@ typedef Butter2<butter100_2_coeffs> butter10hz0_2; //10hz sample, 0.2hz fcut
 
 struct butter100_3_coeffs
 {
-  static const float A1 = 1.7347257688;
-  static const float A2 = -0.7660066009;
-  static const float GAIN = 1.278738361e+02;
+  static constexpr float A1 = 1.7347257688;
+  static constexpr float A2 = -0.7660066009;
+  static constexpr float GAIN = 1.278738361e+02;
 };
 typedef Butter2<butter100_3_coeffs> butter100hz3_0; //100hz sample, 3hz fcut
 typedef Butter2<butter100_3_coeffs> butter50hz1_5; //50hz sample, 1.5hz fcut
@@ -79,9 +81,9 @@ typedef Butter2<butter100_3_coeffs> butter10hz0_3; //10hz sample, 0.3hz fcut
 
 struct butter100_4_coeffs
 {
-  static const float A1 = 1.6474599811;
-  static const float A2 = -0.7008967812;
-  static const float GAIN = 7.485478157e+01;
+  static constexpr float A1 = 1.6474599811;
+  static constexpr float A2 = -0.7008967812;
+  static constexpr float GAIN = 7.485478157e+01;
 };
 typedef Butter2<butter100_4_coeffs> butter100hz4_0; //100hz sample, 4hz fcut
 typedef Butter2<butter100_4_coeffs> butter50hz2_0; //50hz sample, 2hz fcut
@@ -89,9 +91,9 @@ typedef Butter2<butter100_4_coeffs> butter10hz0_4; //10hz sample, .4hz fcut
 
 struct butter100_8_coeffs
 {
-  static const float A1 = 1.3072850288;
-  static const float A2 = -0.4918122372;
-  static const float GAIN = 2.167702007e+01;
+  static constexpr float A1 = 1.3072850288;
+  static constexpr float A2 = -0.4918122372;
+  static constexpr float GAIN = 2.167702007e+01;
 };
 typedef Butter2<butter100_8_coeffs> butter100hz8_0; //100hz sample, 8hz fcut
 typedef Butter2<butter100_8_coeffs> butter50hz4_0; //50hz sample, 4hz fcut
@@ -99,9 +101,9 @@ typedef Butter2<butter100_8_coeffs> butter10hz0_8; //10hz sample, .8hz fcut
 
 struct butter50_8_coeffs
 {
-  static const float A1 = 0.6710290908;
-  static const float A2 = -0.2523246263;
-  static const float GAIN = 6.881181354e+00;
+  static constexpr float A1 = 0.6710290908;
+  static constexpr float A2 = -0.2523246263;
+  static constexpr float GAIN = 6.881181354e+00;
 };
 typedef Butter2<butter50_8_coeffs> butter50hz8_0; //50hz sample, 8hz fcut
 typedef Butter2<butter50_8_coeffs> butter10hz1_6; //10hz sample, 1.6hz fcut