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/
43 import sigrokdecode as srd
46 SE0, J, K, SE1 = 0, 1, 2, 3
58 '10000111': 'OUT', # Tokens
62 '11000011': 'DATA0', # Data
64 '01001011': 'ACK', # Handshake
70 def bitstr_to_num(bitstr):
75 return int(''.join(l), 2)
77 def packet_decode(packet):
80 pid = pids.get(pid, pid)
83 if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
86 data = str(bitstr_to_num(data))
88 dev = bitstr_to_num(data[:7])
89 ep = bitstr_to_num(data[7:])
90 data = 'DEV %d EP %d' % (dev, ep)
92 elif pid in ('DATA0', 'DATA1'):
96 tmp += '%02x ' % bitstr_to_num(data[:8])
102 if sync != '00000001':
103 return 'SYNC INVALID!'
105 return pid + ' ' + data
107 class Decoder(srd.Decoder):
110 longname = 'Universal Serial Bus'
111 desc = 'Universal Serial Bus'
112 longdesc = '...longdesc...'
117 {'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
118 {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
128 def start(self, metadata):
129 self.rate = metadata['samplerate']
131 # self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
132 self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
134 if self.rate < 48000000:
135 raise Exception('Sample rate not sufficient for USB decoding')
137 # Initialise decoder state.
142 def decode(self, ss, es, data):
145 # for (samplenum, (dp, dm, x, y, z, a)) in data:
146 for (samplenum, (dm, dp)) in data:
157 # We ignore single sample width pulses.
158 # I sometimes get these with the OLS.
163 # How many bits since the last transition?
164 if self.packet != '' or self.sym != J:
165 bitcount = int((self.scount - 1) * 12000000 / self.rate)
171 # End-Of-Packet (EOP)
172 self.put(0, 0, self.out_ann,
173 [0, [packet_decode(self.packet), self.packet]])
175 # Longer than EOP, assume reset.
176 self.put(0, 0, self.out_ann, [0, ['RESET']])
182 # Add bits to the packet string.
183 self.packet += '1' * bitcount
185 # Handle bit stuffing.
186 if bitcount < 6 and sym != SE0:
189 self.put(0, 0, self.out_ann, [0, ['BIT STUFF ERROR']])