--- /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 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 sigrokdecode as srd
+
+# States
+SE0, J, K, SE1 = 0, 1, 2, 3
+
+# ...
+syms = {
+ (0, 0): SE0,
+ (1, 0): J,
+ (0, 1): K,
+ (1, 1): SE1,
+}
+
+# ...
+pids = {
+ '10000111': 'OUT', # Tokens
+ '10010110': 'IN',
+ '10100101': 'SOF',
+ '10110100': 'SETUP',
+ '11000011': 'DATA0', # Data
+ '11010010': 'DATA1',
+ '01001011': 'ACK', # Handshake
+ '01011010': 'NAK',
+ '01111000': 'STALL',
+ '01101001': 'NYET',
+}
+
+def bitstr_to_num(bitstr):
+ if not bitstr:
+ return 0
+ l = list(bitstr)
+ l.reverse()
+ return int(''.join(l), 2)
+
+def packet_decode(packet):
+ 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(srd.Decoder):
+ id = 'usb'
+ name = 'USB'
+ longname = 'Universal Serial Bus'
+ desc = 'Universal Serial Bus'
+ longdesc = '...longdesc...'
+ author = 'Gareth McMullin'
+ email = 'gareth@blacksphere.co.nz'
+ license = 'gplv2+'
+ inputs = ['logic']
+ outputs = ['usb']
+ probes = [
+ {'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
+ {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
+ ]
+ options = {}
+ annotations = [
+ ['TODO', 'TODO']
+ ]
+
+ def __init__(self):
+ pass
+
+ def start(self, metadata):
+ self.rate = metadata['samplerate']
+
+ # self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
+ self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
+
+ 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, ss, es, data):
+
+ # FIXME
+ # for (samplenum, (dp, dm, x, y, z, a)) in data:
+ for (samplenum, (dm, dp)) in data:
+
+ self.scount += 1
+
+ sym = syms[dp, 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)
+ self.put(0, 0, self.out_ann,
+ [0, [packet_decode(self.packet), self.packet]])
+ else:
+ # Longer than EOP, assume reset.
+ self.put(0, 0, self.out_ann, [0, ['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:
+ self.put(0, 0, self.out_ann, [0, ['BIT STUFF ERROR']])
+
+ self.scount = 0
+ self.sym = sym
+
projects / libsigrokdecode.git / blobdiff