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
54 def bitstr_to_num(bitstr):
59 return int(''.join(l), 2)
61 def packet_decode(packet):
63 '10000111': 'OUT', # Tokens
67 '11000011': 'DATA0', # Data
69 '01001011': 'ACK', # Handshake
77 pid = pids.get(pid, pid)
80 if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
83 data = str(bitstr_to_num(data))
85 dev = bitstr_to_num(data[:7])
86 ep = bitstr_to_num(data[7:])
87 data = 'DEV %d EP %d' % (dev, ep)
89 elif pid in ('DATA0', 'DATA1'):
93 tmp += '%02X ' % bitstr_to_num(data[:8])
99 if sync != '00000001':
100 return 'SYNC INVALID!'
102 return pid + ' ' + data
104 class Decoder(srd.Decoder):
107 longname = '...longname...'
108 desc = 'Universal Serial Bus'
109 longdesc = '...longdesc...'
110 author = 'Gareth McMullin'
111 email = 'gareth@blacksphere.co.nz'
116 {'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
117 {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
125 def start(self, metadata):
126 self.rate = metadata['samplerate']
127 # self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
128 self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
129 if self.rate < 48000000:
130 raise Exception('Sample rate not sufficient for USB decoding')
131 # Initialise decoder state.
136 def decode(self, timeoffset, duration, data):
140 for (samplenum, (dp, dm, x, y, z, a)) in data:
149 # We ignore single sample width pulses.
150 # I sometimes get these with the OLS.
155 # How many bits since the last transition?
156 if self.packet or self.sym != J:
157 bitcount = int((self.scount - 1) * 12000000 / self.rate)
163 # End-Of-Packet (EOP)
164 out += [{'type': 'usb', 'data': self.packet,
165 'display': packet_decode(self.packet)}]
167 # Longer than EOP, assume reset.
168 out += [{'type': 'usb', 'display': 'RESET'}]
174 # Add bits to the packet string.
175 self.packet += '1' * bitcount
176 # Handle bit stuffing.
177 if bitcount < 6 and sym != SE0:
180 out += [{'type': 'usb', 'display': 'BIT STUFF ERROR'}]
186 # self.put(0, 0, self.out_proto, out_proto)
187 self.put(0, 0, self.out_ann, out)