--- /dev/null
+##
+## 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 singalling consists of two signal lines, both driven at 3.3V
+# logic levels. The signals are DP and DM, 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 transision from J to K
+# or vice-versa indicates a logic 0, while no transision 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.
+
+import sigrok
+
+class Sample():
+ def __init__(self, data):
+ self.data = data
+ def probe(self, probe):
+ s = ord(self.data[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]))
+
+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():
+ 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()
+
+ def start(self, metadata):
+ self.unitsize = metadata['unitsize']
+ self.rate = metadata['samplerate']
+ 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, data):
+ for sample in sampleiter(data['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 = (self.scount - 1) * 12000000 / self.rate
+ else:
+ bitcount = 0
+
+ if self.sym == SE0:
+ if bitcount == 1:
+ # End-Of-Packet
+ sigrok.put({"type":"usb", "data":self.packet,
+ "display":packet_decode(self.packet)})
+ else:
+ # Longer than EOP, assume reset
+ sigrok.put({"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:
+ sigrok.put({"type":"usb", "display":"BIT STUFF ERROR"})
+
+ self.scount = 0
+ self.sym = sym
+
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