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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
## Copyright (C) 2012-2013 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.
# Note: Low-speed J and K are inverted compared to the full-speed J and K!
symbols = {
'low-speed': {
# (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'K',
(0, 1): 'J',
(1, 1): 'SE1',
},
'full-speed': {
# (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'J',
(0, 1): 'K',
(1, 1): 'SE1',
},
}
bitrates = {
'low-speed': 1500000, # 1.5Mb/s (+/- 1.5%)
'full-speed': 12000000, # 12Mb/s (+/- 0.25%)
}
class Decoder(srd.Decoder):
api_version = 1
id = 'usb_signalling'
name = 'USB signalling'
longname = 'Universal Serial Bus (LS/FS) signalling'
desc = 'USB (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.oldsym = 'J' # The "idle" state is J.
self.ss_sop = -1
self.samplenum = 0
self.packet = ''
self.syms = []
self.bitrate = None
self.bitwidth = None
self.bitnum = 0
self.samplenum_target = None
self.oldpins = None
self.consecutive_ones = 0
self.state = 'IDLE'
def start(self, metadata):
self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb_signalling')
self.out_ann = self.add(srd.OUTPUT_ANN, 'usb_signalling')
self.bitrate = bitrates[self.options['signalling']]
self.bitwidth = float(metadata['samplerate']) / float(self.bitrate)
def report(self):
pass
def putpx(self, data):
self.put(self.samplenum, self.samplenum, self.out_proto, data)
def putx(self, data):
self.put(self.samplenum, self.samplenum, self.out_ann, data)
def putpb(self, data):
s, halfbit = self.samplenum, int(self.bitwidth / 2)
self.put(s - halfbit, s + halfbit, self.out_proto, data)
def putb(self, data):
s, halfbit = self.samplenum, int(self.bitwidth / 2)
self.put(s - halfbit, s + halfbit, self.out_ann, data)
def set_new_target_samplenum(self):
bitpos = self.ss_sop + (self.bitwidth / 2)
bitpos += self.bitnum * self.bitwidth
self.samplenum_target = int(bitpos)
def wait_for_sop(self, sym):
# Wait for a Start of Packet (SOP), i.e. a J->K symbol change.
if sym != 'K':
self.oldsym = sym
return
self.ss_sop = self.samplenum
self.set_new_target_samplenum()
self.putpx(['SOP', None])
self.putx([0, ['SOP']])
self.state = 'GET BIT'
def handle_bit(self, sym, b):
if self.consecutive_ones == 6 and b == '0':
# Stuff bit. Don't add to the packet, reset self.consecutive_ones.
self.putb([0, ['SB: %s/%s' % (sym, b)]])
self.consecutive_ones = 0
else:
# Normal bit. Add it to the packet, update self.consecutive_ones.
self.putb([0, ['%s/%s' % (sym, b)]])
self.packet += b
if b == '1':
self.consecutive_ones += 1
else:
self.consecutive_ones = 0
def get_eop(self, sym):
# EOP: SE0 for >= 1 bittime (usually 2 bittimes), then J.
self.syms.append(sym)
self.putpb(['SYM', sym])
self.putb([0, ['%s' % sym]])
self.bitnum += 1
self.set_new_target_samplenum()
self.oldsym = sym
if self.syms[-2:] == ['SE0', 'J']:
# Got an EOP, i.e. we now have a full packet.
self.putpb(['PACKET', self.packet])
self.putb([0, ['PACKET: %s' % self.packet]])
self.bitnum, self.packet, self.syms, self.state = 0, '', [], 'IDLE'
self.consecutive_ones = 0
def get_bit(self, sym):
if sym == 'SE0':
# Start of an EOP. Change state, run get_eop() for this bit.
self.state = 'GET EOP'
self.get_eop(sym)
return
self.syms.append(sym)
self.putpb(['SYM', sym])
b = '0' if self.oldsym != sym else '1'
self.handle_bit(sym, b)
self.bitnum += 1
self.set_new_target_samplenum()
self.oldsym = sym
def decode(self, ss, es, data):
for (self.samplenum, pins) in data:
# State machine.
if self.state == 'IDLE':
# Ignore identical samples early on (for performance reasons).
if self.oldpins == pins:
continue
self.oldpins = pins
sym = symbols[self.options['signalling']][tuple(pins)]
self.wait_for_sop(sym)
elif self.state in ('GET BIT', 'GET EOP'):
# Wait until we're in the middle of the desired bit.
if self.samplenum < self.samplenum_target:
continue
sym = symbols[self.options['signalling']][tuple(pins)]
if self.state == 'GET BIT':
self.get_bit(sym)
elif self.state == 'GET EOP':
self.get_eop(sym)
else:
raise Exception('Invalid state: %s' % self.state)
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