Hi,
I needed to decode the timing between pin changes for the WS2811 protocol,
it requires some strict timing and my code is not up to it so I needed to
measure it. I could do that manually but it was a pain in the ass and very
slow so I whipped up this protocol decoder to calculate the time between
pin changes.
Baruch
diff --git a/decoders/timing/__init__.py b/decoders/timing/__init__.py
new file mode 100644
index 0000000..628ad3f
--- /dev/null
+++ b/decoders/timing/__init__.py
@@ -0,0 +1,25 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Torsten Duwe <d...@suse.de>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+##
+
+'''
+Timing decoder, find the time between pulses.
+'''
+
+from .pd import Decoder
diff --git a/decoders/timing/pd.py b/decoders/timing/pd.py
new file mode 100644
index 0000000..d62b569
--- /dev/null
+++ b/decoders/timing/pd.py
@@ -0,0 +1,95 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Torsten Duwe <d...@suse.de>
+## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourde...@savoirfairelinux.com>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+##
+
+import sigrokdecode as srd
+
+class SamplerateError(Exception):
+ pass
+
+def normalize_time(t):
+ if t >= 1.0:
+ return '%.3f sec' % t
+ elif t >= 0.001:
+ return '%.3f msec' % (t*1000.0)
+ elif t >= 0.000001:
+ return '%.3f usec' % (t*1000.0*1000.0)
+ elif t >= 0.000000001:
+ return '%.3f nsec' % (t*1000.0 * 1000.0 * 1000.0)
+ else:
+ return '%f' % t
+
+class Decoder(srd.Decoder):
+ api_version = 2
+ id = 'timing'
+ name = 'Timing'
+ longname = 'Timing Finder'
+ desc = 'Calculate time between pulses.'
+ license = 'gplv2+'
+ inputs = ['logic']
+ outputs = ['timing']
+ channels = (
+ {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
+ )
+ annotations = (
+ ('time', 'Time'),
+ )
+ annotation_rows = (
+ ('time', 'Time', (0,)),
+ )
+
+ def __init__(self, **kwargs):
+ self.samplerate = None
+ self.oldpin = None
+ self.last_samplenum = None
+
+ def metadata(self, key, value):
+ if key == srd.SRD_CONF_SAMPLERATE:
+ self.samplerate = value
+
+ def start(self):
+ self.out_ann = self.register(srd.OUTPUT_ANN)
+
+ def decode(self, ss, es, data):
+ if not self.samplerate:
+ raise SamplerateError('Cannot decode without samplerate.')
+
+ # Initialize self.oldpins with the first sample value.
+ for (samplenum, (pin0,)) in data:
+ # Ignore identical samples early on (for performance reasons).
+ if self.oldpin == pin0:
+ continue
+
+ if self.oldpin is None:
+ self.oldpin = pin0
+ self.last_samplenum = samplenum
+ continue
+
+ if self.oldpin != pin0:
+ samples = samplenum - self.last_samplenum
+ t = samples / self.samplerate
+
+ # Report the timing normalized
+ self.put(self.last_samplenum, samplenum, self.out_ann, [0, [normalize_time(t)]])
+
+ # Store data for next round
+ self.last_samplenum = samplenum
+ self.oldpin = pin0
+
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