ir_nec: concentrate timing at the top of the source file

Move IR NEC protocol timing details to the top of the source file, for
raised awareness and easier adjustment. Specs are "unit-less" (only have
comments), but are scaled for improved readability. Values are copies of
the previous implementation.

1 files changed, 19 insertions, 8 deletions

diff --git a/decoders/ir_nec/pd.py b/decoders/ir_nec/pd.py
index 3c272db..ecd2b7a 100644
--- a/decoders/ir_nec/pd.py
+++ b/decoders/ir_nec/pd.py
@@ -21,6 +21,17 @@ from common.srdhelper import bitpack
 from .lists import *
 import sigrokdecode as srd
 
+# Concentrate all timing constraints of the IR protocol here in a single
+# location at the top of the source, to raise awareness and to simplify
+# review and adjustment.
+_TIME_TOL  =  5 # tolerance, in percent
+_TIME_LC   = 13.5 # leader code, in ms
+_TIME_RC   = 11.25 # repeat code, in ms
+_TIME_ZERO =  1.125 # zero data bit, in ms
+_TIME_ONE  =  2.25 # one data bit, in ms
+_TIME_STOP =  0.652 # stop bit, in ms
+_TIME_IDLE = 20.0 # inter frame timeout, in ms, arbitrary choice
+
 class SamplerateError(Exception):
     pass
 
@@ -48,7 +59,7 @@ class Decoder(srd.Decoder):
     options = (
         {'id': 'polarity', 'desc': 'Polarity', 'default': 'active-low',
             'values': ('auto', 'active-low', 'active-high')},
-        {'id': 'tolerance', 'desc': 'Timing tolerance (%)', 'default': 5},
+        {'id': 'tolerance', 'desc': 'Timing tolerance (%)', 'default': _TIME_TOL},
         {'id': 'cd_freq', 'desc': 'Carrier Frequency', 'default': 0},
         {'id': 'extended', 'desc': 'Extended NEC Protocol',
             'default': 'no', 'values': ('yes', 'no')},
@@ -137,13 +148,13 @@ class Decoder(srd.Decoder):
             self.samplerate = value
 
     def calc_rate(self):
-        self.tolerance = self.options['tolerance'] / 100 # 5% by default
-        self.lc = int(self.samplerate * 0.0135) - 1 # 13.5ms
-        self.rc = int(self.samplerate * 0.01125) - 1 # 11.25ms
-        self.dazero = int(self.samplerate * 0.001125) - 1 # 1.125ms
-        self.daone = int(self.samplerate * 0.00225) - 1 # 2.25ms
-        self.stop = int(self.samplerate * 0.000652) - 1 # 0.652ms
-        self.idle_to = int(self.samplerate * 0.020) - 1 # 20ms, arbitrary choice
+        self.tolerance = self.options['tolerance'] / 100
+        self.lc = int(self.samplerate * _TIME_LC / 1000) - 1
+        self.rc = int(self.samplerate * _TIME_RC / 1000) - 1
+        self.dazero = int(self.samplerate * _TIME_ZERO / 1000) - 1
+        self.daone = int(self.samplerate * _TIME_ONE / 1000) - 1
+        self.stop = int(self.samplerate * _TIME_STOP / 1000) - 1
+        self.idle_to = int(self.samplerate * _TIME_IDLE / 1000) - 1
 
     def compare_with_tolerance(self, measured, base):
         return (measured >= base * (1 - self.tolerance)