ir_nec: sort and comment timing specs, drop tolerance option

Extend comments on the IR NEC timing details. Sort the symbols by their
width to reflect their relation (ONE to ZERO to STOP is each half of
their predecessor's width).

Increase the open coded tolerance percentage, and remove the option for
the value. Make sure leader and repeat codes still can be told from each
other.

diff --git a/decoders/ir_nec/pd.py b/decoders/ir_nec/pd.py
index ecd2b7a170fce1a5580273944585f450280e4c4a..f5c479913c0258dcdba26dd6ef3391e2974e546c 100644 (file)
--- a/decoders/ir_nec/pd.py
+++ b/decoders/ir_nec/pd.py
@@ -23,14 +23,16 @@ 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
+# review and adjustment. The tolerance is an arbitrary choice, available
+# literature does not mention any. The inter-frame timeout is not a part
+# of the protocol, but an implementation detail of this sigrok decoder.
+_TIME_TOL  =  8     # tolerance, in percent
+_TIME_IDLE = 20.0   # inter-frame timeout, in ms
+_TIME_LC   = 13.5   # leader code, in ms
+_TIME_RC   = 11.25  # repeat code, in ms
+_TIME_ONE  =  2.25  # one data bit, 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
@@ -59,7 +61,6 @@ class Decoder(srd.Decoder):
     options = (
         {'id': 'polarity', 'desc': 'Polarity', 'default': 'active-low',
             'values': ('auto', 'active-low', 'active-high')},
-        {'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')},
@@ -148,7 +149,7 @@ class Decoder(srd.Decoder):
             self.samplerate = value
 
     def calc_rate(self):
-        self.tolerance = self.options['tolerance'] / 100
+        self.tolerance = _TIME_TOL / 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