Miller encoding PD

2 files changed, 209 insertions, 0 deletions

diff --git a/decoders/miller/__init__.py b/decoders/miller/__init__.py
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+++ b/decoders/miller/__init__.py
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+##
+## 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/>.
+##
+
+'''
+The Miller protocol decoder supports (modified) Miller encoded data.
+
+Used in NFC communication at 106 kbaud.
+'''
+
+from .pd import Decoder
diff --git a/decoders/miller/pd.py b/decoders/miller/pd.py
new file mode 100644
index 0000000..7ccd75e
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+++ b/decoders/miller/pd.py
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+##
+## 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/>.
+##
+
+# http://www.gorferay.com/type-a-communications-interface/
+# https://resources.infosecinstitute.com/introduction-rfid-security/
+# https://www.radio-electronics.com/info/wireless/nfc/near-field-communications-modulation-rf-signal-interface.php
+# https://www.researchgate.net/figure/Modified-Miller-Code_fig16_283498836
+
+# Miller: either edge
+# modified Miller: falling edge
+
+import sigrokdecode as srd
+
+def roundto(x, k=1.0):
+    return round(x / k) * k
+
+class Decoder(srd.Decoder):
+    api_version = 3
+    id = 'miller'
+    name = 'Miller'
+    longname = 'Miller decoder for NFC'
+    desc = 'Decodes (modified) Miller encoding as used in NFC communication.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['miller']
+    channels = (
+        {'id': 'data', 'name': 'Data', 'desc': 'Data signal'},
+    )
+    options = (
+        {'id': 'baudrate', 'desc': 'Baud rate', 'default': 106000},
+        {'id': 'edge', 'desc': 'Edge', 'default': 'falling', 'values': ('rising', 'falling', 'either')},
+    )
+    annotations = (
+        ('bit', 'Bit'),
+        ('bitstring', 'Bitstring'),
+    )
+    annotation_rows = tuple((u, v, (i,)) for i, (u, v) in enumerate(annotations))
+
+    def __init__(self):
+        self.samplerate = 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.out_binary = self.register(srd.OUTPUT_BINARY)
+
+    def decode_bits(self):
+        timeunit = self.samplerate / self.options['baudrate']
+        edgetype = self.options['edge'][0]
+
+        self.wait({0: edgetype}) # first symbol, beginning of unit
+        prevedge = self.samplenum
+
+        # start of message: '0'
+        prevbit = 0
+        yield (0, prevedge, prevedge + timeunit)
+        expectedstart = self.samplenum + timeunit
+
+        # end of message: '0' followed by one idle symbol
+
+        while True:
+            self.wait([{0: edgetype}, {'skip': int(3 * timeunit)}])
+            got_timeout = self.matched[1]
+            sampledelta = (self.samplenum - prevedge)
+            prevedge = self.samplenum
+            timedelta = roundto(sampledelta / timeunit, 0.5)
+
+            # a mark stands for a 1 bit
+            # a mark has an edge in the middle
+
+            # a space stands for a 0 bit
+            # a space either has an edge at the beginning or no edge at all
+            # after a mark, a space is edge-less
+            # after a space, a space has an edge
+
+            # we get 1.0, 1.5, 2.0 times between edges
+
+            # end of transmission is always a space, either edged or edge-less
+
+            if prevbit == 0: # space -> ???
+                if timedelta == 1.0: # 1.0 units -> space
+                    yield (0, self.samplenum, self.samplenum + timeunit)
+                    prevbit = 0
+                    expectedstart = self.samplenum + timeunit
+                elif timedelta == 1.5: # 1.5 units -> mark
+                    yield (1, expectedstart, self.samplenum + 0.5*timeunit)
+                    prevbit = 1
+                    expectedstart = self.samplenum + timeunit*0.5
+                elif timedelta >= 2.0:
+                    # idle symbol (end of message)
+                    yield None
+                else:
+                    # assert timedelta >= 2.0
+                    yield (False, self.samplenum - sampledelta, self.samplenum)
+                    break
+            else: # mark -> ???
+                if timedelta <= 0.5:
+                    yield (False, self.samplenum - sampledelta, self.samplenum)
+                    break
+                if timedelta == 1.0: # 1.0 units -> mark again (1.5 from start)
+                    yield (1, expectedstart, self.samplenum + 0.5*timeunit)
+                    prevbit = 1
+                    expectedstart = self.samplenum + 0.5*timeunit
+                elif timedelta == 1.5: # 1.5 units -> space (no pulse) and space (pulse)
+                    yield (0, expectedstart, self.samplenum)
+                    yield (0, self.samplenum, self.samplenum + timeunit)
+                    prevbit = 0
+                    expectedstart = self.samplenum + timeunit
+                elif timedelta == 2.0: # 2.0 units -> space (no pulse) and mark (pulse)
+                    yield (0, expectedstart, expectedstart + timeunit)
+                    yield (1, self.samplenum - 0.5*timeunit, self.samplenum + 0.5*timeunit)
+                    prevbit = 1
+                    expectedstart = self.samplenum + timeunit*0.5
+                else: # longer -> space and end of message
+                    yield (0, expectedstart, expectedstart + timeunit)
+                    yield None
+                    break
+
+    def decode_run(self):
+        numbits = 0
+        bitvalue = 0
+        bitstring = ''
+        stringstart = None
+        stringend = None
+
+        for bit in self.decode_bits():
+            if bit is None:
+                break
+
+            (value, ss, es) = bit
+
+            if value is False:
+                self.put(int(ss), int(es), self.out_ann, [1, ['ERROR']])
+            else:
+                self.put(int(ss), int(es), self.out_ann, [0, ['{}'.format(value)]])
+
+            if value is False:
+                numbits = 0
+                break
+
+            if stringstart is None:
+                stringstart = ss
+
+            stringend = es
+
+            bitvalue |= value << numbits
+            numbits += 1
+
+            bitstring += '{}'.format(value)
+            if numbits % 4 == 0:
+                bitstring += ' '
+
+        if not numbits:
+            return
+
+        self.put(int(stringstart), int(stringend), self.out_ann, [1, ['{}'.format(bitstring)]])
+
+        numbytes = numbits // 8 + (numbits % 8 > 0)
+        bytestring = bitvalue.to_bytes(numbytes, 'little')
+        self.put(int(stringstart), int(stringend), self.out_binary, [1, bytestring])
+
+    def decode(self):
+        while True:
+            self.decode_run()