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
|
##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2023 Eric Anderson <ejona86@gmail.com>
##
## 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 SamplerateError(Exception):
pass
class Decoder(srd.Decoder):
"""
Python protocol: Each datum is a tuple, with the first entry being a string
denoting its type:
- HALFBIT: Contains a second entry of either 0 or 1, the value of one half
of a bitcell
- DISCONT: The data stream dropped and there is a discontinuity
- IDX: Index pulse
"""
api_version = 3
id = 'mfm'
name = 'FM/MFM'
longname = '(Modified) Frequency Modulation'
desc = 'Floppy disk FM/MFM raw half-bits.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['mfm']
tags = ['Encoding', 'PC', 'Retro computing']
channels = (
{'id': 'data', 'name': 'RD/WD', 'desc': 'Flux pulses'},
)
optional_channels = (
{'id': 'idx', 'name': 'IDX', 'desc': 'Index pulses'},
{'id': 'enablelo', 'name': 'Enable low', 'desc': 'Decode when low'},
{'id': 'enablehi', 'name': 'Enable high', 'desc': 'Decode when high'},
)
annotations = (
('halfbit', 'Clock and data'),
('err', 'Clock Error'),
)
annotation_rows = (
('bit', 'Clock and data', (0,)),
('errs', 'Errors', (1,)),
)
options = (
{
'id': 'data_rate',
'desc': 'Data rate (kbps)',
'default': 250,
'values': (
125,
150,
250,
300,
500,
1000,
5000)},
{
'id': 'leading_edge',
'desc': 'Leading edge',
'default': 'falling',
'values': ('falling', 'rising')})
def __init__(self):
self.samplerate = None
self.wait_cond = 'f'
self.data_rate = 0.0 # Hz
def reset(self):
self.__init__()
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
def start(self):
rising = self.options['leading_edge'] == 'rising'
self.wait_cond = 'r' if rising else 'f'
self.data_rate = float(self.options['data_rate']) * 1000
self.out_ann = self.register(srd.OUTPUT_ANN)
self.out_py = self.register(srd.OUTPUT_PYTHON)
def decode(self):
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
window_size = int(self.samplerate / self.data_rate / 2)
window_size_half = int(self.samplerate / self.data_rate / 4)
b = 0
bit_start = self.samplenum
consecutive_zeros = 0
skip = window_size
while True:
last_samplenum = self.samplenum
_, _, enLo, enHi = self.wait([
{0: self.wait_cond},
{'skip': skip},
{1: self.wait_cond}])
if self.matched[2]:
self.put(self.samplenum, self.samplenum, self.out_py, ('IDX',))
if not (self.matched[0] or self.matched[1]):
skip -= self.samplenum - last_samplenum
continue
if enLo == 1:
self.put(self.samplenum, self.samplenum, self.out_py,
('DISCONT',))
self.wait({2: 'l'})
bit_start = self.samplenum
consecutive_zeros = 0
continue
if enHi == 0:
self.put(self.samplenum, self.samplenum, self.out_py,
('DISCONT',))
self.wait({3: 'h'})
bit_start = self.samplenum
consecutive_zeros = 0
continue
b = int(self.matched[0])
bit_end = self.samplenum
skip = window_size
if b:
# Wait returns with zeros aligned to the end of the
# half-bitcell and ones aligned to the center. Add half a
# window for ones to get past the previous half-bitcell.
bit_end += int(.5 * window_size)
skip += window_size_half
consecutive_zeros = 0
else:
consecutive_zeros += 1
if consecutive_zeros > 32:
self.put(bit_start, bit_end, self.out_py, ('DISCONT',))
# Stop decoding until there is another pulse
self.wait({0: self.wait_cond})
bit_start = self.samplenum
consecutive_zeros = 0
continue
if self.samplenum < bit_start:
# Two edges in one half-bitcell
self.put(bit_start, bit_end, self.out_ann,
[1, ['Spurious pulse', 'extra']])
elif consecutive_zeros > 4: # Allow MMFM
self.put(bit_start, bit_end, self.out_ann,
[1, ['No clock', 'clk']])
self.put(bit_start, bit_end, self.out_ann, [0, [str(b)]])
self.put(bit_start, bit_end, self.out_py, ('HALFBIT', b))
bit_start = bit_end
|
