2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
5 ## Copyright (C) 2012-2013 Uwe Hermann <uwe@hermann-uwe.de>
7 ## This program is free software; you can redistribute it and/or modify
8 ## it under the terms of the GNU General Public License as published by
9 ## the Free Software Foundation; either version 2 of the License, or
10 ## (at your option) any later version.
12 ## This program is distributed in the hope that it will be useful,
13 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
14 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 ## GNU General Public License for more details.
17 ## You should have received a copy of the GNU General Public License
18 ## along with this program; if not, write to the Free Software
19 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 # USB signalling (low-speed and full-speed) protocol decoder
24 import sigrokdecode as srd
26 # Low-/full-speed symbols (used as states of our state machine, too).
27 # Note: Low-speed J and K are inverted compared to the full-speed J and K!
29 # (<dp>, <dm>): <symbol/state>
36 # (<dp>, <dm>): <symbol/state>
44 'low-speed': 1500000, # 1.5Mb/s (+/- 1.5%)
45 'full-speed': 12000000, # 12Mb/s (+/- 0.25%)
48 class Decoder(srd.Decoder):
51 name = 'USB signalling'
52 longname = 'Universal Serial Bus (LS/FS) signalling'
53 desc = 'USB (low-speed and full-speed) signalling protocol.'
56 outputs = ['usb_signalling']
58 {'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
59 {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
63 'signalling': ['Signalling', 'full-speed'],
66 ['Text', 'Human-readable text']
70 self.sym = 'J' # The "idle" state is J.
79 def start(self, metadata):
80 self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb_signalling')
81 self.out_ann = self.add(srd.OUTPUT_ANN, 'usb_signalling')
82 self.bitrate = bitrates[self.options['signalling']]
83 self.bitwidth = float(metadata['samplerate']) / float(self.bitrate)
89 self.put(self.samplenum, self.samplenum, self.out_proto, data)
92 self.put(self.samplenum, self.samplenum, self.out_ann, data)
94 def decode(self, ss, es, data):
95 for (self.samplenum, pins) in data:
97 # Note: self.samplenum is the absolute sample number, whereas
98 # self.scount only counts the number of samples since the
99 # last change in the D+/D- lines.
102 # Ignore identical samples early on (for performance reasons).
103 if self.oldpins == pins:
105 self.oldpins, (dp, dm) = pins, pins
107 if self.options['signalling'] == 'low-speed':
108 sym = symbols_ls[dp, dm]
109 elif self.options['signalling'] == 'full-speed':
110 sym = symbols_fs[dp, dm]
112 self.putx([0, [sym]])
113 self.putp(['SYM', sym])
115 # Wait for a symbol change (i.e., change in D+/D- lines).
120 ## self.syms.append(sym + ' ')
121 ## if len(self.syms) == 16:
122 ## self.putx([0, [''.join(self.syms)]])
126 # How many bits since the last transition?
127 if self.packet != '' or self.sym != 'J':
128 bitcount = int((self.scount - 1) / self.bitwidth)
132 if self.sym == 'SE0':
134 # End-Of-Packet (EOP)
135 # self.putx([0, [packet_decode(self.packet), self.packet]])
136 if self.packet != '': # FIXME?
137 self.putx([0, ['PACKET: %s' % self.packet]])
138 self.putp(['PACKET', self.packet])
140 # Longer than EOP, assume reset.
141 self.putx([0, ['RESET']])
142 self.putp(['RESET', None])
143 # self.putx([0, [self.packet]])
149 # Add bits to the packet string.
150 self.packet += '1' * bitcount
152 # Handle bit stuffing.
153 if bitcount < 6 and sym != 'SE0':
156 self.putx([0, ['BIT STUFF ERROR']])
157 self.putp(['BIT STUFF ERROR', None])