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##
## This file is part of the sigrok project.
##
## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
##
## 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 signalling (low-speed and full-speed) protocol decoder
import sigrokdecode as srd
# Low-/full-speed symbols (used as states of our state machine, too).
# Note: Low-speed J and K are inverted compared to the full-speed J and K!
symbols_ls = {
# (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'K',
(0, 1): 'J',
(1, 1): 'SE1',
}
symbols_fs = {
# (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'J',
(0, 1): 'K',
(1, 1): 'SE1',
}
class Decoder(srd.Decoder):
api_version = 1
id = 'usb_signalling'
name = 'USB signalling'
longname = 'Universal Serial Bus (LS/FS) signalling'
desc = 'USB 1.x (low-speed and full-speed) signalling protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['usb_signalling']
probes = [
{'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
{'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
]
optional_probes = []
options = {
'signalling': ['Signalling', 'full-speed'],
}
annotations = [
['Text', 'Human-readable text']
]
def __init__(self):
self.sym = 'J' # The "idle" state is J.
self.samplenum = 0
self.scount = 0
self.packet = ''
self.syms = []
def start(self, metadata):
self.samplerate = metadata['samplerate']
self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb_signalling')
self.out_ann = self.add(srd.OUTPUT_ANN, 'usb_signalling')
def report(self):
pass
def decode(self, ss, es, data):
for (self.samplenum, (dp, dm)) in data:
# Note: self.samplenum is the absolute sample number, whereas
# self.scount only counts the number of samples since the
# last change in the D+/D- lines.
self.scount += 1
if self.options['signalling'] == 'low-speed':
sym = symbols_ls[dp, dm]
elif self.options['signalling'] == 'full-speed':
sym = symbols_fs[dp, dm]
self.put(0, 0, self.out_ann, [0, [sym]])
self.put(0, 0, self.out_proto, ['SYM', sym])
# Wait for a symbol change (i.e., change in D+/D- lines).
if sym == self.sym:
continue
## # Debug code:
## self.syms.append(sym + ' ')
## if len(self.syms) == 16:
## self.put(0, 0, self.out_ann, [0, [''.join(self.syms)]])
## self.syms = []
# continue
# How many bits since the last transition?
if self.packet != '' or self.sym != 'J':
if self.options['signalling'] == 'low-speed':
bitrate = 1500000 # 1.5Mb/s (+/- 1.5%)
elif self.options['signalling'] == 'full-speed':
bitrate = 12000000 # 12Mb/s (+/- 0.25%)
bitcount = int((self.scount - 1) * bitrate / self.samplerate)
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]])
if self.packet != '': # FIXME?
self.put(0, 0, self.out_ann, [0, ['PACKET: %s' % self.packet]])
self.put(0, 0, self.out_proto, ['PACKET', self.packet])
else:
# Longer than EOP, assume reset.
self.put(0, 0, self.out_ann, [0, ['RESET']])
self.put(0, 0, self.out_proto, ['RESET', None])
# self.put(0, 0, self.out_ann, [0, [self.packet]])
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.put(0, 0, self.out_proto, ['BIT STUFF ERROR', None])
self.scount = 0
self.sym = sym
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