From b4d5293d045d68822ad5b2d0a7a5f392c596a0ba Mon Sep 17 00:00:00 2001
From: jaseg <git-bigdata-wsl-arch@jaseg.de>
Date: Mon, 9 Mar 2020 10:17:14 +0100
Subject: decoding WIP

---
 controller/fw/tools/butter_filter_gen.py | 35 +++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

(limited to 'controller/fw/tools')

diff --git a/controller/fw/tools/butter_filter_gen.py b/controller/fw/tools/butter_filter_gen.py
index c77a6ec..0bb81bc 100644
--- a/controller/fw/tools/butter_filter_gen.py
+++ b/controller/fw/tools/butter_filter_gen.py
@@ -18,11 +18,21 @@ def wrap(left='{', right='}', file=None, end=''):
 def print_include_guards(macro_name):
     print(f'#ifndef {macro_name}')
     print(f'#define {macro_name}')
+    print()
     yield
+    print()
     print(f'#endif /* {macro_name} */')
 
 macro_float = lambda f: f'{f}'.replace('.', 'F').replace('-', 'N').replace('+', 'P')
 
+ordinal = lambda n: "%d%s" % (n,"tsnrhtdd"[(n//10%10!=1)*(n%10<4)*n%10::4])
+
+SI_TABLE = {-18: 'a', -15: 'f', -12: 'p', -9: 'n', -6: 'µ', -3: 'm', 0: '', 3: 'k', 6: 'M', 9: 'G', 12: 'T', 15: 'P', 18: 'E'}
+def siprefix(x, space=' ', unit=''):
+    l = math.log10(x)//3*3
+    if l in SI_TABLE:
+        return f'{x/10**l}{space}{SI_TABLE[l]}{unit}'
+    return f'{x}{space}{unit}'
 
 if __name__ == '__main__':
     import argparse
@@ -36,10 +46,17 @@ if __name__ == '__main__':
     sos = sig.butter(args.n, args.fc, fs=args.fs, output='sos')
 
     print('/* THIS IS A GENERATED FILE. DO NOT EDIT! */')
+    print()
     with print_include_guards(f'__BUTTER_FILTER_GENERATED_{args.n}_{macro_float(args.fc)}_{macro_float(args.fs)}__'):
+
+        print(f'/* {ordinal(args.n)} order Butterworth IIR filter coefficients')
+        print(f' *')
+        print(f' * corner frequency f_c = {siprefix(args.fc)}Hz')
+        print(f' * sampling rate f_s = {siprefix(args.fs)}Hz')
+        print(f' */')
+        print()
         print(f'#define {args.macro_name.upper()}_ORDER {args.n}')
         print(f'#define {args.macro_name.upper()}_CLEN {(args.n+1)//2}')
-        print(f'#define {args.macro_name.upper()}_COEFF ', end='')
 
         # scipy.signal.butter by default returns extremely small bs for the first biquad and large ones for subsequent
         # sections. Balance magnitudes to reduce possible rounding errors.
@@ -48,10 +65,14 @@ if __name__ == '__main__':
         mags = [approx_mag // len(sos)] * len(sos)
         mags[0] += approx_mag - sum(mags)
         sos[0][:3] /= 10**approx_mag
+        sos = np.array([ sec * np.array([10**mag, 10**mag, 10**mag, 1, 1, 1]) for mag, sec in zip(mags, sos) ])
+
+        ones = np.ones([100000])
+        _, steady_state = sig.sosfilt(sos, ones, zi=np.zeros([(args.n+1)//2, 2]))
 
-        for mag, sec in zip(mags, sos):
+        print(f'#define {args.macro_name.upper()}_COEFF ', end='')
+        for sec in sos:
             bs, ases = sec[:3], sec[4:6]
-            bs *= 10**mag
 
             with wrap():
                 print('.b=', end='')
@@ -62,3 +83,11 @@ if __name__ == '__main__':
                     print(', '.join(f'{v}' for v in ases), end='')
             print(', ', end='')
         print()
+
+        print(f'#define {args.macro_name.upper()}_STEADY_STATE ', end='')
+        for sec in steady_state:
+            with wrap():
+                print(', '.join(f'{v}' for v in sec), end='')
+            print(', ', end='')
+        print()
+
-- 
cgit