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
21 # USB Full-speed protocol decoder
23 # Full-speed usb singalling consists of two signal lines, both driven at 3.3V
24 # logic levels. The signals are DP and DM, and normally operate in
26 # The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K.
27 # A state SE0 is defined where DP=DM=0. This common mode signal is used to
28 # signal a reset or end of packet.
30 # Data transmitted on the USB is encoded with NRZI. A transision from J to K
31 # or vice-versa indicates a logic 0, while no transision indicates a logic 1.
32 # If 6 ones are transmitted consecutively, a zero is inserted to force a
33 # transition. This is known as bit stuffing. Data is transferred at a rate
34 # of 12Mbit/s. The SE0 transmitted to signal an end-of-packet is two bit
40 def __init__(self, data):
42 def probe(self, probe):
43 s = ord(self.data[probe / 8]) & (1 << (probe % 8))
44 return True if s else False
46 def sampleiter(data, unitsize):
47 for i in range(0, len(data), unitsize):
48 yield(Sample(data[i:i+unitsize]))
50 SE0, J, K, SE1 = 0, 1, 2, 3
58 def bitstr_to_num(bitstr):
59 if not bitstr: return 0
62 return int(''.join(l), 2)
64 def packet_decode(packet):
65 pids = {'10000111':'OUT', #Tokens
69 '11000011':'DATA0', #Data
71 '01001011':'ACK', #Handshake
79 pid = pids.get(pid, pid)
81 if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
84 data = str(bitstr_to_num(data))
86 dev = bitstr_to_num(data[:7])
87 ep = bitstr_to_num(data[7:])
88 data = "DEV %d EP %d" % (dev, ep)
90 elif pid in ('DATA0', 'DATA1'):
94 tmp += "%02X " % bitstr_to_num(data[:8])
100 if sync != "00000001":
101 return "SYNC INVALID!"
103 return pid + ' ' + data
107 desc = 'Universal Serial Bus'
108 longname = '...longname...'
109 longdesc = '...longdesc...'
110 author = 'Gareth McMullin'
111 email = 'gareth@blacksphere.co.nz'
115 # Probe names with a set of defaults
116 probes = {'dp':0, 'dm':1}
120 self.probes = Decoder.probes.copy()
122 def start(self, metadata):
123 self.unitsize = metadata['unitsize']
124 self.rate = metadata['samplerate']
125 if self.rate < 48000000:
126 raise Exception("Sample rate not sufficient for USB decoding")
127 # initialise decoder state
132 def decode(self, data):
133 for sample in sampleiter(data['data'], self.unitsize):
137 sym = syms[sample.probe(self.probes['dp']),
138 sample.probe(self.probes['dm'])]
143 # We ignore single sample width pulses.
144 # I sometimes get these with the OLS
149 # how many bits since the last transition?
150 if self.packet or self.sym != J:
151 bitcount = (self.scount - 1) * 12000000 / self.rate
158 sigrok.put({"type":"usb", "data":self.packet,
159 "display":packet_decode(self.packet)})
161 # Longer than EOP, assume reset
162 sigrok.put({"type":"usb", "display":"RESET"})
168 # Add bits to the packet string.
169 self.packet += '1' * bitcount
170 # Handle bit stuffing
171 if bitcount < 6 and sym != SE0:
174 sigrok.put({"type":"usb", "display":"BIT STUFF ERROR"})