Add a PWM decoder.

2 files changed, 122 insertions, 0 deletions

diff --git a/decoders/pwm/__init__.py b/decoders/pwm/__init__.py
new file mode 100644
index 0000000..096e077
--- /dev/null
+++ b/decoders/pwm/__init__.py
@@ -0,0 +1,25 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Torsten Duwe <duwe@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
+##
+
+'''
+Pulse-width modulation (a.k.a pulse-duration modulation, PDM) decoder.
+'''
+
+from .pd import Decoder
diff --git a/decoders/pwm/pd.py b/decoders/pwm/pd.py
new file mode 100644
index 0000000..999b496
--- /dev/null
+++ b/decoders/pwm/pd.py
@@ -0,0 +1,97 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Torsten Duwe <duwe@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
+##
+
+import sigrokdecode as srd
+
+class Decoder(srd.Decoder):
+    api_version = 2
+    id = 'pwm'
+    name = 'PWM'
+    longname = 'Pulse-width modulation'
+    desc = 'Analog level encoded in duty cycle percentage.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['pwm']
+    channels = (
+        {'id': 'pwm', 'name': 'PWM in', 'desc': 'Modulation pulses'},
+    )
+    options = (
+        {'id': 'new_cycle_edge', 'desc': 'New cycle on which edge',
+            'default': 'rising', 'values': ('rising', 'falling')},
+    )
+    annotations = (
+        ('value', 'PWM value'),
+    )
+    binary = (
+        ('raw', 'RAW file'),
+    )
+
+    def __init__(self, **kwargs):
+        self.ss = self.es = -1
+        self.high = 1
+        self.low = 1
+        self.lastedge = 0
+        self.oldpin = 0
+        self.startedge = 0
+        self.num_cycles = 0
+
+    def start(self):
+        self.out_python = self.register(srd.OUTPUT_PYTHON)
+        self.out_ann = self.register(srd.OUTPUT_ANN)
+        self.out_bin = self.register(srd.OUTPUT_BINARY)
+        self.out_freq = self.register(srd.OUTPUT_META,
+            meta=(int, 'Frequency', 'PWM base (cycle) frequency'))
+        self.startedge = 0
+        if self.options['new_cycle_edge'] == 'falling':
+            self.startedge = 1
+
+    def putx(self, data):
+        self.put(self.ss, self.es, self.out_ann, data)
+
+    def putp(self, data):
+        self.put(self.ss, self.es, self.out_python, data)
+
+    def putb(self, data):
+        self.put(self.num_cycles, self.num_cycles, self.out_bin, data)
+
+    def decode(self, ss, es, data):
+        for (self.samplenum, pins) in data:
+            # Ignore identical samples early on (for performance reasons).
+            if self.oldpin == pins[0]:
+                continue
+
+            if self.oldpin == 0: # Rising edge.
+                self.low = self.samplenum - self.lastedge
+            else:
+                self.high = self.samplenum - self.lastedge
+
+            if self.oldpin == self.startedge:
+                self.es = self.samplenum # This interval ends at this edge.
+                if self.ss >= 0: # Have we completed a hi-lo sequence?
+                    self.putx([0, ["%d%%" % ((100 * self.high) // (self.high + self.low))]])
+                    self.putb((0, bytes([(256 * self.high) // (self.high + self.low)])))
+                self.num_cycles += 1
+            else:
+                # Mid-interval.
+                # This interval started at the previous edge.
+                self.ss = self.lastedge
+
+            self.lastedge = self.samplenum
+            self.oldpin = pins[0]