2 ## This file is part of the sigrok project.
4 ## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
6 ## This program is free software; you can redistribute it and/or modify
7 ## it under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 2 of the License, or
9 ## (at your option) any later version.
11 ## This program is distributed in the hope that it will be useful,
12 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ## GNU General Public License for more details.
16 ## You should have received a copy of the GNU General Public License
17 ## along with this program; if not, write to the Free Software
18 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 # USB Full-speed protocol decoder
24 # Full-speed USB signalling consists of two signal lines, both driven at 3.3V
25 # logic levels. The signals are DP (D+) and DM (D-), and normally operate in
27 # The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K.
28 # A state SE0 is defined where DP=DM=0. This common mode signal is used to
29 # signal a reset or end of packet.
31 # Data transmitted on the USB is encoded with NRZI. A transition from J to K
32 # or vice-versa indicates a logic 0, while no transition indicates a logic 1.
33 # If 6 ones are transmitted consecutively, a zero is inserted to force a
34 # transition. This is known as bit stuffing. Data is transferred at a rate
35 # of 12Mbit/s. The SE0 transmitted to signal an end-of-packet is two bit
39 # https://en.wikipedia.org/wiki/USB
40 # http://www.usb.org/developers/docs/
46 def __init__(self, data):
48 def probe(self, probe):
49 s = ord(self.data[probe / 8]) & (1 << (probe % 8))
50 return True if s else False
52 def sampleiter(data, unitsize):
53 for i in range(0, len(data), unitsize):
54 yield(Sample(data[i:i+unitsize]))
57 SE0, J, K, SE1 = 0, 1, 2, 3
65 def bitstr_to_num(bitstr):
66 if not bitstr: return 0
69 return int(''.join(l), 2)
71 def packet_decode(packet):
73 '10000111':'OUT', # Tokens
77 '11000011':'DATA0', # Data
79 '01001011':'ACK', # Handshake
87 pid = pids.get(pid, pid)
89 if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
92 data = str(bitstr_to_num(data))
94 dev = bitstr_to_num(data[:7])
95 ep = bitstr_to_num(data[7:])
96 data = "DEV %d EP %d" % (dev, ep)
98 elif pid in ('DATA0', 'DATA1'):
102 tmp += "%02X " % bitstr_to_num(data[:8])
108 if sync != "00000001":
109 return "SYNC INVALID!"
111 return pid + ' ' + data
115 desc = 'Universal Serial Bus'
116 longname = '...longname...'
117 longdesc = '...longdesc...'
118 author = 'Gareth McMullin'
119 email = 'gareth@blacksphere.co.nz'
123 # Probe names with a set of defaults
124 probes = {'dp':0, 'dm':1}
128 self.probes = Decoder.probes.copy()
130 def start(self, metadata):
131 self.unitsize = metadata['unitsize']
132 self.rate = metadata['samplerate']
133 if self.rate < 48000000:
134 raise Exception("Sample rate not sufficient for USB decoding")
135 # Initialise decoder state.
140 def decode(self, data):
141 for sample in sampleiter(data['data'], self.unitsize):
145 sym = syms[sample.probe(self.probes['dp']),
146 sample.probe(self.probes['dm'])]
151 # We ignore single sample width pulses.
152 # I sometimes get these with the OLS.
157 # How many bits since the last transition?
158 if self.packet or self.sym != J:
159 bitcount = (self.scount - 1) * 12000000 / self.rate
165 # End-Of-Packet (EOP)
166 sigrok.put({"type":"usb", "data":self.packet,
167 "display":packet_decode(self.packet)})
169 # Longer than EOP, assume reset.
170 sigrok.put({"type":"usb", "display":"RESET"})
176 # Add bits to the packet string.
177 self.packet += '1' * bitcount
178 # Handle bit stuffing.
179 if bitcount < 6 and sym != SE0:
182 sigrok.put({"type":"usb", "display":"BIT STUFF ERROR"})