Add a gray code and rotary encoder protocol decoder.

2 files changed, 230 insertions, 0 deletions

diff --git a/decoders/graycode/__init__.py b/decoders/graycode/__init__.py
new file mode 100644
index 0000000..90ef824
--- /dev/null
+++ b/decoders/graycode/__init__.py
@@ -0,0 +1,24 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2017 Christoph Rackwitz <christoph.rackwitz@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/>.
+##
+
+'''
+Gray code and rotary encoder protocol.
+'''
+
+from .pd import Decoder
diff --git a/decoders/graycode/pd.py b/decoders/graycode/pd.py
new file mode 100644
index 0000000..2edc837
--- /dev/null
+++ b/decoders/graycode/pd.py
@@ -0,0 +1,206 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2017 Christoph Rackwitz <christoph.rackwitz@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 math
+import sigrokdecode as srd
+from collections import deque
+
+def bitpack(bits):
+    res = 0
+    for i, b in enumerate(bits):
+        res |= b << i
+    return res
+
+def bitunpack(num, minbits=0):
+    res = []
+    while num or minbits > 0:
+        res.append(num & 1)
+        num >>= 1
+        minbits -= 1
+    return tuple(res)
+
+def gray_encode(plain):
+    return plain & (plain >> 1)
+
+def gray_decode(gray):
+    temp = gray
+    temp ^= (temp >> 8)
+    temp ^= (temp >> 4)
+    temp ^= (temp >> 2)
+    temp ^= (temp >> 1)
+    return temp
+
+def prefix_fmt(value, emin=None):
+    sgn = (value > 0) - (value < 0)
+    value = abs(value)
+    p = math.log10(value) if value else 0
+    value = sgn * math.floor(value * 10**int(3 - p)) * 10**-int(3 - p)
+    e = p // 3 * 3
+    if emin is not None and e < emin:
+        e = emin
+    value *= 10**-e
+    p -= e
+    decimals = 2 - int(p)
+    prefixes = {-9: 'n', -6: 'µ', -3: 'm', 0: '', 3: 'k', 6: 'M', 9: 'G'}
+    return '{0:.{1}f} {2}'.format(value, decimals, prefixes[e])
+
+class ChannelMapError(Exception):
+    pass
+
+class Value:
+    def __init__(self, onchange):
+        self.onchange = onchange
+        self.timestamp = None
+        self.value = None
+
+    def get(self):
+        return self.value
+
+    def set(self, timestamp, newval):
+        if newval != self.value:
+            if self.value is not None:
+                self.onchange(self.timestamp, self.value, timestamp, newval)
+
+            self.value = newval
+            self.timestamp = timestamp
+        elif False:
+            if self.value is not None:
+                self.onchange(self.timestamp, self.value, timestamp, newval)
+
+MAX_CHANNELS = 8 # 10 channels causes some weird problems...
+
+class Decoder(srd.Decoder):
+    api_version = 3
+    id = 'graycode'
+    name = 'Gray code'
+    longname = 'Gray code and rotary encoder'
+    desc = 'Accumulate rotary encoder increments, provide timing statistics.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['graycode']
+    optional_channels = tuple(
+        {'id': 'd{}'.format(i), 'name': 'D{}'.format(i), 'desc': 'Data line {}'.format(i)}
+        for i in range(MAX_CHANNELS)
+    )
+    options = (
+        {'id': 'edges', 'desc': 'Edges per rotation', 'default': 0},
+        {'id': 'avg_period', 'desc': 'Averaging period', 'default': 10},
+    )
+    annotations = (
+        ('phase', 'Phase'),
+        ('increment', 'Increment'),
+        ('count', 'Count'),
+        ('turns', 'Turns'),
+        ('interval', 'Interval'),
+        ('average', 'Average'),
+        ('rpm', 'Rate'),
+    )
+    annotation_rows = tuple((u, v, (i,)) for i, (u, v) in enumerate(annotations))
+
+    def __init__(self):
+        self.num_channels = 0
+        self.samplerate = None
+        self.last_n = deque()
+
+        self.phase = Value(self.on_phase)
+        self.increment = Value(self.on_increment)
+        self.count = Value(self.on_count)
+        self.turns = Value(self.on_turns)
+
+    def on_phase(self, told, vold, tnew, vnew):
+        self.put(told, tnew, self.out_ann, [0, ['{}'.format(vold)]])
+
+    def on_increment(self, told, vold, tnew, vnew):
+        if vold == 0:
+            message = '0'
+        elif abs(vold) == self.ENCODER_STEPS // 2:
+            message = '±π'
+        else:
+            message = '{:+d}'.format(vold)
+        self.put(told, tnew, self.out_ann, [1, [message]])
+
+    def on_count(self, told, vold, tnew, vnew):
+        self.put(told, tnew, self.out_ann, [2, ['{}'.format(vold)]])
+
+    def on_turns(self, told, vold, tnew, vnew):
+        self.put(told, tnew, self.out_ann, [3, ['{:+d}'.format(vold)]])
+
+    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):
+        chmask = [self.has_channel(i) for i in range(MAX_CHANNELS)]
+        self.num_channels = sum(chmask)
+        if chmask != [i < self.num_channels for i in range(MAX_CHANNELS)]:
+            raise ChannelMapError('Assigned channels need to be contiguous')
+
+        self.ENCODER_STEPS = 1 << self.num_channels
+
+        startbits = self.wait()
+        curtime = self.samplenum
+
+        self.turns.set(self.samplenum, 0)
+        self.count.set(self.samplenum, 0)
+        self.phase.set(self.samplenum, gray_decode(bitpack(startbits[:self.num_channels])))
+
+        while True:
+            prevtime = curtime
+            bits = self.wait([{i: 'e'} for i in range(self.num_channels)])
+            curtime = self.samplenum
+
+            oldcount = self.count.get()
+            oldphase = self.phase.get()
+
+            newphase = gray_decode(bitpack(bits[:self.num_channels]))
+            self.phase.set(self.samplenum, newphase)
+
+            phasedelta_raw = (newphase - oldphase + (self.ENCODER_STEPS // 2 - 1)) % self.ENCODER_STEPS - (self.ENCODER_STEPS // 2 - 1)
+            phasedelta = phasedelta_raw
+            self.increment.set(self.samplenum, phasedelta)
+            if abs(phasedelta) == self.ENCODER_STEPS // 2:
+                phasedelta = 0
+
+            self.count.set(self.samplenum, self.count.get() + phasedelta)
+
+            if self.options['edges']:
+                self.turns.set(self.samplenum, self.count.get() // self.options['edges'])
+
+            if self.samplerate is not None:
+                period = (curtime - prevtime) / self.samplerate
+                freq = abs(phasedelta_raw) / period
+
+                self.put(prevtime, curtime, self.out_ann, [4, [
+                    '{}s, {}Hz'.format(prefix_fmt(period), prefix_fmt(freq))]])
+
+                if self.options['avg_period']:
+                    self.last_n.append((abs(phasedelta_raw), period))
+                    if len(self.last_n) > self.options['avg_period']:
+                        self.last_n.popleft()
+
+                    avg_period = sum(v for u, v in self.last_n) / (sum(u for u, v in self.last_n) or 1)
+                    self.put(prevtime, curtime, self.out_ann, [5, [
+                        '{}s, {}Hz'.format(prefix_fmt(avg_period),
+                            prefix_fmt(1 / avg_period))]])
+
+                if self.options['edges']:
+                    self.put(prevtime, curtime, self.out_ann, [6, ['{}rpm'.format(prefix_fmt(60 * freq / self.options['edges'], emin=0))]])