Hi everyone, Measuring the simple timing of a pulse edge is the kind of thing I'd usually just do some quick scripting for, but I figured it's nice to be able to look at the data directly in pulseview as well so I wrote a very simple encoder.
Here's a shot of pulseview with two of these decoders loaded: http://i.imgur.com/ZfsZ2pg.png Can measure across high/low/edge-to-edge/falling-to-falling or rising-to-rising. I've attached a patch. Happy to change/cleanup it in any way if necessary, or be told that this isn't the right approach for this kind of thing. I haven't written any tests, but I can easily make some from existing dumps if it's useful to have them. Angus
>From 057317c216b1d8116b57a31db19cf01a1aaf8f89 Mon Sep 17 00:00:00 2001 From: Angus Gratton <[email protected]> Date: Wed, 29 Oct 2014 09:19:38 +1100 Subject: [PATCH] pulsewidth: Add a simple decoder for measuring timing of pulses. Can measure duration of an edge, or time between edge transitions --- decoders/pulsewidth/__init__.py | 25 +++++++++ decoders/pulsewidth/pd.py | 115 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 140 insertions(+) create mode 100644 decoders/pulsewidth/__init__.py create mode 100644 decoders/pulsewidth/pd.py diff --git a/decoders/pulsewidth/__init__.py b/decoders/pulsewidth/__init__.py new file mode 100644 index 0000000..0238108 --- /dev/null +++ b/decoders/pulsewidth/__init__.py @@ -0,0 +1,25 @@ +## +## This file is part of the libsigrokdecode project. +## +## Copyright (C) 2014 Angus Gratton <[email protected]> +## +## 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 +## + +''' +Simple decoder of pulse width times (either duration of an edge, or time between edge transitions.) +''' + +from .pd import Decoder diff --git a/decoders/pulsewidth/pd.py b/decoders/pulsewidth/pd.py new file mode 100644 index 0000000..a08f3e5 --- /dev/null +++ b/decoders/pulsewidth/pd.py @@ -0,0 +1,115 @@ +## encoding: utf-8 +## +## This file is part of the libsigrokdecode project. +## +## Copyright (C) 2014 Angus Gratton <[email protected]> +## +## 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 +import re + +''' +OUTPUT_PYTHON format: + +Packet: +[<width>] (seconds of pulse width, floating point) +''' + +class Decoder(srd.Decoder): + api_version = 2 + id = 'pulsewidth' + name = 'Pulse Width' + longname = 'Pulse Width' + desc = 'Simple measurement of pulse durations.' + license = 'gplv2+' + inputs = ['logic'] + outputs = ['pulsewidth'] + channels = ( + {'id': 'pulse', 'name': 'Pulse', 'desc': 'Data pulse to measure'}, + ) + options = ( + {'id': 'pulse_type', + 'desc': 'Pulse type to measure', + 'default': 'low', 'values': ('low', 'high', 'edge_to_edge', 'falling_to_falling', 'rising_to_rising')}, + ) + annotations = ( + ('low', 'LOW'), + ('high', 'HIGH'), + ) + + def __init__(self, **kwargs): + self.last_pulse = -1 + self.samplerate = None + self.start_sample = None + self.start_pol = -1 + self.last_sample = None + + def start(self): + self.out_ann = self.register(srd.OUTPUT_ANN) + self.out_python = self.register(srd.OUTPUT_PYTHON) + + def metadata(self, key, value): + if key == srd.SRD_CONF_SAMPLERATE: + self.samplerate = value + + def decode(self, ss, es, data): + if self.samplerate is None: + raise Exception('Cannot decode without samplerate.') + pulse_type = self.options['pulse_type'] + for (samplenum, (pulse,)) in data: + if self.start_sample is not None: + # currently measuring a pulse + is_end = { + 'low' : pulse == 1, + 'high' : pulse == 0, + 'edge_to_edge' : pulse != self.last_pulse, + 'falling_to_falling' : pulse == 0 and self.last_pulse == 1, + 'rising_to_rising' : pulse == 1 and self.last_pulse == 0 }[pulse_type] + if is_end: + self.put_pulse(self.start_sample, self.last_sample) + self.start_sample = None + else: + self.last_sample = samplenum + if self.start_sample is None: + # not currently measuring a pulse + is_start = { + 'low' : pulse == 0, + 'high' : pulse == 1, + 'edge_to_edge' : pulse != self.last_pulse, + 'falling_to_falling' : pulse == 0 and self.last_pulse == 1, + 'rising_to_rising' : pulse ==1 and self.last_pulse == 0 }[pulse_type] + if is_start: + self.start_sample = samplenum + self.start_pol = pulse + self.last_sample = samplenum + self.last_pulse = pulse + + def put_pulse(self, start, end): + start_ts = float(start) / self.samplerate + end_ts = float(end) / self.samplerate + delta = end_ts - start_ts + if delta <= 1e-6: + delta_s = u"%.1fns" % (delta * 1e9) + elif delta <= 1e-3: + delta_s = u"%.1fμs" % (delta * 1e6) + elif delta <= 1: + delta_s = u"%.1fms" % (delta * 1e3) + else: + delta_s = u"%.1s" % (delta) + # self.start_pol 0,1 maps to annotation 0,1 for annotating lows/highs differently + self.put(start, end, self.out_ann, [self.start_pol, [delta_s]]) + self.put(start, end, self.out_python, [delta]) -- 2.1.0
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