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##
## This file is part of the sigrok project.
##
## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
#
# USB Full-speed protocol decoder
#
# Full-speed USB signalling consists of two signal lines, both driven at 3.3V
# logic levels. The signals are DP (D+) and DM (D-), and normally operate in
# differential mode.
# The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K.
# A state SE0 is defined where DP=DM=0. This common mode signal is used to
# signal a reset or end of packet.
#
# Data transmitted on the USB is encoded with NRZI. A transition from J to K
# or vice-versa indicates a logic 0, while no transition indicates a logic 1.
# If 6 ones are transmitted consecutively, a zero is inserted to force a
# transition. This is known as bit stuffing. Data is transferred at a rate
# of 12Mbit/s. The SE0 transmitted to signal an end-of-packet is two bit
# intervals long.
#
# Details:
# https://en.wikipedia.org/wiki/USB
# http://www.usb.org/developers/docs/
#
import sigrok
class Sample():
def __init__(self, data):
self.data = data
def probe(self, probe):
s = ord(self.data[int(probe / 8)]) & (1 << (probe % 8))
return True if s else False
def sampleiter(data, unitsize):
for i in range(0, len(data), unitsize):
yield(Sample(data[i:i+unitsize]))
# States
SE0, J, K, SE1 = 0, 1, 2, 3
syms = {
(False, False): SE0,
(True, False): J,
(False, True): K,
(True, True): SE1,
}
def bitstr_to_num(bitstr):
if not bitstr: return 0
l = list(bitstr)
l.reverse()
return int(''.join(l), 2)
def packet_decode(packet):
pids = {
'10000111':'OUT', # Tokens
'10010110':'IN',
'10100101':'SOF',
'10110100':'SETUP',
'11000011':'DATA0', # Data
'11010010':'DATA1',
'01001011':'ACK', # Handshake
'01011010':'NAK',
'01111000':'STALL',
'01101001':'NYET',
}
sync = packet[:8]
pid = packet[8:16]
pid = pids.get(pid, pid)
# Remove CRC.
if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
data = packet[16:-5]
if pid == 'SOF':
data = str(bitstr_to_num(data))
else:
dev = bitstr_to_num(data[:7])
ep = bitstr_to_num(data[7:])
data = "DEV %d EP %d" % (dev, ep)
elif pid in ('DATA0', 'DATA1'):
data = packet[16:-16]
tmp = ""
while data:
tmp += "%02X " % bitstr_to_num(data[:8])
data = data[8:]
data = tmp
else:
data = packet[16:]
if sync != "00000001":
return "SYNC INVALID!"
return pid + ' ' + data
class Decoder(sigrok.Decoder):
id = 'usb'
name = 'USB'
desc = 'Universal Serial Bus'
longname = '...longname...'
longdesc = '...longdesc...'
author = 'Gareth McMullin'
email = 'gareth@blacksphere.co.nz'
license = 'gplv2+'
inputs = ['logic']
outputs = ['usb']
# Probe names with a set of defaults
probes = {'dp':0, 'dm':1}
options = {}
def __init__(self):
self.probes = Decoder.probes.copy()
self.output_protocol = None
self.output_annotation = None
def start(self, metadata):
self.unitsize = metadata['unitsize']
self.rate = metadata['samplerate']
# self.output_protocol = self.output_new(2)
self.output_annotation = self.output_new(1)
if self.rate < 48000000:
raise Exception("Sample rate not sufficient for USB decoding")
# Initialise decoder state.
self.sym = J
self.scount = 0
self.packet = ''
def decode(self, timeoffset, duration, data):
out = []
for sample in sampleiter(data, self.unitsize):
self.scount += 1
sym = syms[sample.probe(self.probes['dp']),
sample.probe(self.probes['dm'])]
if sym == self.sym:
continue
if self.scount == 1:
# We ignore single sample width pulses.
# I sometimes get these with the OLS.
self.sym = sym
self.scount = 0
continue
# How many bits since the last transition?
if self.packet or self.sym != J:
bitcount = int((self.scount - 1) * 12000000 / self.rate)
else:
bitcount = 0
if self.sym == SE0:
if bitcount == 1:
# End-Of-Packet (EOP)
out += [{"type":"usb", "data":self.packet,
"display":packet_decode(self.packet)}]
else:
# Longer than EOP, assume reset.
out += [{"type":"usb", "display":"RESET"}]
self.scount = 0
self.sym = sym
self.packet = ''
continue
# Add bits to the packet string.
self.packet += '1' * bitcount
# Handle bit stuffing.
if bitcount < 6 and sym != SE0:
self.packet += '0'
elif bitcount > 6:
out += [{"type":"usb", "display":"BIT STUFF ERROR"}]
self.scount = 0
self.sym = sym
if out != []:
# self.put(self.output_protocol, 0, 0, out_proto)
self.put(self.output_annotation, 0, 0, out)
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