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 SE0, J, K, SE1 = 0, 1, 2, 3
54 def bitstr_to_num(bitstr):
55 if not bitstr: return 0
58 return int(''.join(l), 2)
60 def packet_decode(packet):
62 '10000111':'OUT', # Tokens
66 '11000011':'DATA0', # Data
68 '01001011':'ACK', # Handshake
76 pid = pids.get(pid, pid)
78 if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
81 data = str(bitstr_to_num(data))
83 dev = bitstr_to_num(data[:7])
84 ep = bitstr_to_num(data[7:])
85 data = "DEV %d EP %d" % (dev, ep)
87 elif pid in ('DATA0', 'DATA1'):
91 tmp += "%02X " % bitstr_to_num(data[:8])
97 if sync != "00000001":
98 return "SYNC INVALID!"
100 return pid + ' ' + data
102 class Decoder(sigrokdecode.Decoder):
105 desc = 'Universal Serial Bus'
106 longname = '...longname...'
107 longdesc = '...longdesc...'
108 author = 'Gareth McMullin'
109 email = 'gareth@blacksphere.co.nz'
113 # Probe names with a set of defaults
115 {'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
116 {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
121 self.output_protocol = None
122 self.output_annotation = None
124 def start(self, metadata):
125 self.rate = metadata['samplerate']
126 # self.output_protocol = self.output_new(2)
127 self.output_annotation = self.output_new(1)
128 if self.rate < 48000000:
129 raise Exception("Sample rate not sufficient for USB decoding")
130 # Initialise decoder state.
135 def decode(self, timeoffset, duration, data):
139 for (samplenum, (dp, dm, x, y, z, a)) in data:
148 # We ignore single sample width pulses.
149 # I sometimes get these with the OLS.
154 # How many bits since the last transition?
155 if self.packet or self.sym != J:
156 bitcount = int((self.scount - 1) * 12000000 / self.rate)
162 # End-Of-Packet (EOP)
163 out += [{"type":"usb", "data":self.packet,
164 "display":packet_decode(self.packet)}]
166 # Longer than EOP, assume reset.
167 out += [{"type":"usb", "display":"RESET"}]
173 # Add bits to the packet string.
174 self.packet += '1' * bitcount
175 # Handle bit stuffing.
176 if bitcount < 6 and sym != SE0:
179 out += [{"type":"usb", "display":"BIT STUFF ERROR"}]
185 # self.put(0, 0, self.output_protocol, out_proto)
186 self.put(0, 0, self.output_annotation, out)