1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
##
## 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 encoding'
desc = 'Miller encoding protocol.'
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))
binary = (
('raw', 'Raw binary'),
)
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, [0, bytestring])
def decode(self):
while True:
self.decode_run()
|
