Add a trivial "counter" decoder

This decoder just counts the number of falling and/or rising edges. This
is especially useful for diagnosing protocols with a clock signal or a
fixed number of transitions per bit, e.g. pulse length coded.

It also provides a divider, which can be used to e.g. count the number
of words in I²C or SPI transfers.

2 files changed, 123 insertions, 0 deletions

diff --git a/decoders/counter/__init__.py b/decoders/counter/__init__.py
new file mode 100644
index 0000000..e731311
--- /dev/null
+++ b/decoders/counter/__init__.py
@@ -0,0 +1,28 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2018 Stefan Brüns <stefan.bruens@rwth-aachen.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, see <http://www.gnu.org/licenses/>.
+##
+
+'''
+This PD is a simple counter.
+
+It can count rising and/or falling edges, provides an optional reset
+signal. It can also divide the count to e.g. count the numger of
+fixed length words (where a word corresponds to e.g. 9 clock edges).
+'''
+
+from .pd import Decoder
diff --git a/decoders/counter/pd.py b/decoders/counter/pd.py
new file mode 100644
index 0000000..e32dabd
--- /dev/null
+++ b/decoders/counter/pd.py
@@ -0,0 +1,95 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2018 Stefan Brüns <stefan.bruens@rwth-aachen.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, see <http://www.gnu.org/licenses/>.
+##
+
+import sigrokdecode as srd
+
+class Decoder(srd.Decoder):
+    api_version = 3
+    id = 'counter'
+    name = 'Counter'
+    longname = 'Edge counter'
+    desc = 'Count number of edges.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = []
+    channels = (
+        {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
+    )
+    optional_channels = (
+        {'id': 'reset', 'name': 'Reset', 'desc': 'Reset line'},
+    )
+    annotations = (
+        ('edge_count', 'Edge count'),
+        ('word_count', 'Word count'),
+    )
+    annotation_rows = (
+        ('edge_counts', 'Edges', (0,)),
+        ('word_counts', 'Words', (1,)),
+    )
+    options = (
+        {'id': 'edge', 'desc': 'Edges to check', 'default': 'any', 'values': ('any', 'rising', 'falling')},
+        {'id': 'divider', 'desc': 'Count divider (word width)', 'default': 0},
+    )
+
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.edge_count = 0
+        self.word_count = 0
+        self.have_reset = 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)
+        self.edge = self.options['edge']
+        self.divider = self.options['divider']
+        if self.divider < 0:
+            self.divider = 0
+
+    def put_count(self, ann_class, count):
+        self.put(self.samplenum, self.samplenum, self.out_ann,
+            [ann_class, [str(count)]])
+
+    def decode(self):
+        condition = [{'rising':  {0: 'r'},
+                      'falling': {0: 'f'},
+                      'any':     {0: 'e'},}[self.edge]]
+
+        if self.has_channel(1):
+            self.have_reset = True
+            condition.append({1: 'f'})
+
+        while True:
+            self.wait(condition)
+            if self.have_reset and self.matched[1]:
+                self.edge_count = 0
+                self.word_count = 0
+                self.put_count(1, 'R')
+                continue
+
+            self.edge_count += 1
+
+            self.put_count(0, self.edge_count)
+            if self.divider > 0 and (self.edge_count % self.divider) == 0:
+                self.word_count += 1
+                self.put_count(1, self.word_count)