[libsigrokdecode.git] / decoders / onewire_link / onewire_link.py

##
## This file is part of the sigrok project.
##
## Copyright (C) 2012 Iztok Jeras <iztok.jeras@gmail.com>
##
## 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
##

# 1-Wire protocol decoder (link layer)

import sigrokdecode as srd

class Decoder(srd.Decoder):
    api_version = 1
    id = 'onewire_link'
    name = '1-Wire link layer'
    longname = '1-Wire serial communication bus (link layer)'
    desc = 'Bidirectional, half-duplex, asynchronous serial bus.'
    license = 'gplv2+'
    inputs = ['logic']
    outputs = ['onewire_link']
    probes = [
        {'id': 'owr', 'name': 'OWR', 'desc': '1-Wire signal line'},
    ]
    optional_probes = [
        {'id': 'pwr', 'name': 'PWR', 'desc': '1-Wire power supply pin'},
    ]
    options = {
        'overdrive': ['Overdrive', 1],
        # Time options (specified in number of samplerate periods):
        'cnt_normal_bit': ['Normal mode sample bit time', 0],
        'cnt_normal_slot': ['Normal mode data slot time', 0],
        'cnt_normal_presence': ['Normal mode sample presence time', 0],
        'cnt_normal_reset': ['Normal mode reset time', 0],
        'cnt_overdrive_bit': ['Overdrive mode sample bit time', 0],
        'cnt_overdrive_slot': ['Overdrive mode data slot time', 0],
        'cnt_overdrive_presence': ['Overdrive mode sample presence time', 0],
        'cnt_overdrive_reset': ['Overdrive mode reset time', 0],
    }
    annotations = [
        ['Text', 'Human-readable text'],
        ['Warnings', 'Human-readable warnings'],
    ]

    def __init__(self, **kwargs):
        self.samplenum = 0
        self.state = 'WAIT FOR FALLING EDGE'
        self.present = 0
        self.bit = 0
        self.bit_cnt = 0
        self.command = 0
        self.overdrive = 0
        self.fall = 0
        self.rise = 0

    def start(self, metadata):
        self.out_proto = self.add(srd.OUTPUT_PROTO, 'onewire_link')
        self.out_ann = self.add(srd.OUTPUT_ANN, 'onewire_link')

        self.samplerate = metadata['samplerate']

        # Check if samplerate is appropriate.
        if self.options['overdrive']:
            if self.samplerate < 2000000:
                self.put(0, 0, self.out_ann, [1,
                    ['ERROR: Sampling rate is too low. Must be above 2MHz ' +
                     'for proper overdrive mode decoding.']])
            elif self.samplerate < 5000000:
                self.put(0, 0, self.out_ann, [1,
                  ['WARNING: Sampling rate is suggested to be above 5MHz ' +
                   'for proper overdrive mode decoding.']])
        else:
            if self.samplerate < 400000:
                self.put(0, 0, self.out_ann, [1,
                    ['ERROR: Sampling rate is too low. Must be above ' +
                     '400kHz for proper normal mode decoding.']])
            elif (self.samplerate < 1000000):
                self.put(0, 0, self.out_ann, [1,
                    ['WARNING: Sampling rate is suggested to be above ' +
                     '1MHz for proper normal mode decoding.']])

        # The default 1-Wire time base is 30us. This is used to calculate
        # sampling times.
        samplerate = float(self.samplerate)
        if self.options['cnt_normal_bit']:
            self.cnt_normal_bit = self.options['cnt_normal_bit']
        else:
            self.cnt_normal_bit = int(samplerate * 0.000015) - 1 # 15ns
        if self.options['cnt_normal_slot']:
            self.cnt_normal_slot = self.options['cnt_normal_slot']
        else:
            self.cnt_normal_slot = int(samplerate * 0.000060) - 1 # 60ns
        if self.options['cnt_normal_presence']:
            self.cnt_normal_presence = self.options['cnt_normal_presence']
        else:
            self.cnt_normal_presence = int(samplerate * 0.000075) - 1 # 75ns
        if self.options['cnt_normal_reset']:
            self.cnt_normal_reset = self.options['cnt_normal_reset']
        else:
            self.cnt_normal_reset = int(samplerate * 0.000480) - 1 # 480ns
        if self.options['cnt_overdrive_bit']:
            self.cnt_overdrive_bit = self.options['cnt_overdrive_bit']
        else:
            self.cnt_overdrive_bit = int(samplerate * 0.000002) - 1 # 2ns
        if self.options['cnt_overdrive_slot']:
            self.cnt_overdrive_slot = self.options['cnt_overdrive_slot']
        else:
            self.cnt_overdrive_slot = int(samplerate * 0.0000073) - 1 # 6ns+1.3ns
        if self.options['cnt_overdrive_presence']:
            self.cnt_overdrive_presence = self.options['cnt_overdrive_presence']
        else:
            self.cnt_overdrive_presence = int(samplerate * 0.000010) - 1 # 10ns
        if self.options['cnt_overdrive_reset']:
            self.cnt_overdrive_reset = self.options['cnt_overdrive_reset']
        else:
            self.cnt_overdrive_reset = int(samplerate * 0.000048) - 1 # 48ns

        # Organize values into lists.
        self.cnt_bit = [self.cnt_normal_bit, self.cnt_overdrive_bit]
        self.cnt_presence = [self.cnt_normal_presence, self.cnt_overdrive_presence]
        self.cnt_reset = [self.cnt_normal_reset, self.cnt_overdrive_reset]
        self.cnt_slot = [self.cnt_normal_slot, self.cnt_overdrive_slot]

        # Check if sample times are in the allowed range.

        time_min = float(self.cnt_normal_bit) / self.samplerate
        time_max = float(self.cnt_normal_bit + 1) / self.samplerate
        if (time_min < 0.000005) or (time_max > 0.000015):
            self.put(0, 0, self.out_ann, [1,
                ['WARNING: The normal mode data sample time interval ' +
                 '(%2.1fus-%2.1fus) should be inside (5.0us, 15.0us).'
                 % (time_min * 1000000, time_max * 1000000)]])

        time_min = float(self.cnt_normal_presence) / self.samplerate
        time_max = float(self.cnt_normal_presence + 1) / self.samplerate
        if (time_min < 0.0000681) or (time_max > 0.000075):
            self.put(0, 0, self.out_ann, [1,
                ['WARNING: The normal mode presence sample time interval ' +
                 '(%2.1fus-%2.1fus) should be inside (68.1us, 75.0us).'
                 % (time_min * 1000000, time_max * 1000000)]])

        time_min = float(self.cnt_overdrive_bit) / self.samplerate
        time_max = float(self.cnt_overdrive_bit + 1) / self.samplerate
        if (time_min < 0.000001) or (time_max > 0.000002):
            self.put(0, 0, self.out_ann, [1,
                ['WARNING: The overdrive mode data sample time interval ' +
                 '(%2.1fus-%2.1fus) should be inside (1.0us, 2.0us).'
                 % (time_min * 1000000, time_max * 1000000)]])

        time_min = float(self.cnt_overdrive_presence) / self.samplerate
        time_max = float(self.cnt_overdrive_presence + 1) / self.samplerate
        if (time_min < 0.0000073) or (time_max > 0.000010):
            self.put(0, 0, self.out_ann, [1,
                ['WARNING: The overdrive mode presence sample time interval ' +
                 '(%2.1fus-%2.1fus) should be inside (7.3us, 10.0us).'
                 % (time_min*1000000, time_max*1000000)]])

    def report(self):
        pass

    def decode(self, ss, es, data):
        for (self.samplenum, (owr, pwr)) in data:
            # State machine.
            if self.state == 'WAIT FOR FALLING EDGE':
                # The start of a cycle is a falling edge.
                if owr != 0:
                    continue
                # Save the sample number for the falling edge.
                self.fall = self.samplenum
                # Go to waiting for sample time.
                self.state = 'WAIT FOR DATA SAMPLE'
            elif self.state == 'WAIT FOR DATA SAMPLE':
                # Sample data bit.
                t = self.samplenum - self.fall
                if t == self.cnt_bit[self.overdrive]:
                    self.bit = owr
                    self.state = 'WAIT FOR DATA SLOT END'
            elif self.state == 'WAIT FOR DATA SLOT END':
                # A data slot ends in a recovery period, otherwise, this is
                # probably a reset.
                t = self.samplenum - self.fall
                if t != self.cnt_slot[self.overdrive]:
                    continue

                if owr == 0:
                    # This seems to be a reset slot, wait for its end.
                    self.state = 'WAIT FOR RISING EDGE'
                    continue

                self.put(self.fall, self.samplenum, self.out_ann,
                         [0, ['Bit: %d' % self.bit]])
                self.put(self.fall, self.samplenum, self.out_proto,
                         ['BIT', self.bit])

                # Checking the first command to see if overdrive mode
                # should be entered.
                if self.bit_cnt <= 8:
                    self.command |= (self.bit << self.bit_cnt)
                elif self.bit_cnt == 8 and self.command in [0x3c, 0x69]:
                    self.put(self.fall, self.cnt_bit[self.overdrive],
                             self.out_ann, [0, ['Entering overdrive mode']])
                # Increment the bit counter.
                self.bit_cnt += 1
                # Wait for next slot.
                self.state = 'WAIT FOR FALLING EDGE'
            elif self.state == 'WAIT FOR RISING EDGE':
                # The end of a cycle is a rising edge.
                if owr != 1:
                    continue

                # Check if this was a reset cycle.
                t = self.samplenum - self.fall
                if t > self.cnt_normal_reset:
                    # Save the sample number for the falling edge.
                    self.rise = self.samplenum
                    self.state = 'WAIT FOR PRESENCE DETECT'
                    # Exit overdrive mode.
                    if self.overdrive:
                        self.put(self.fall, self.cnt_bit[self.overdrive],
                                 self.out_ann, [0, ['Exiting overdrive mode']])
                        self.overdrive = 0
                    # Clear command bit counter and data register.
                    self.bit_cnt = 0
                    self.command = 0
                elif (t > self.cnt_overdrive_reset) and self.overdrive:
                    # Save the sample number for the falling edge.
                    self.rise = self.samplenum
                    self.state = "WAIT FOR PRESENCE DETECT"
                # Otherwise this is assumed to be a data bit.
                else:
                    self.state = "WAIT FOR FALLING EDGE"
            elif self.state == 'WAIT FOR PRESENCE DETECT':
                # Sample presence status.
                t = self.samplenum - self.rise
                if t == self.cnt_presence[self.overdrive]:
                    self.present = owr
                    self.state = 'WAIT FOR RESET SLOT END'
            elif self.state == 'WAIT FOR RESET SLOT END':
                # A reset slot ends in a long recovery period.
                t = self.samplenum - self.rise
                if t != self.cnt_reset[self.overdrive]:
                    continue

                if owr == 0:
                    # This seems to be a reset slot, wait for its end.
                    self.state = 'WAIT FOR RISING EDGE'
                    continue

                self.put(self.fall, self.samplenum, self.out_ann,
                         [0, ['Reset/presence: %s'
                         % ('false' if self.present else 'true')]])
                self.put(self.fall, self.samplenum, self.out_proto,
                         ['RESET/PRESENCE', not self.present])
                # Wait for next slot.
                self.state = 'WAIT FOR FALLING EDGE'
            else:
                raise Exception('Invalid state: %s' % self.state)
Commit	Line	Data
9cfb16e8 IJ	1	##
	2	## This file is part of the sigrok project.
	3	##
	4	## Copyright (C) 2012 Iztok Jeras <iztok.jeras@gmail.com>
	5	##
	6	## This program is free software; you can redistribute it and/or modify
	7	## it under the terms of the GNU General Public License as published by
	8	## the Free Software Foundation; either version 2 of the License, or
	9	## (at your option) any later version.
	10	##
	11	## This program is distributed in the hope that it will be useful,
	12	## but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	## GNU General Public License for more details.
	15	##
	16	## You should have received a copy of the GNU General Public License
	17	## along with this program; if not, write to the Free Software
	18	## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	19	##
	20
e7720d6c	21	# 1-Wire protocol decoder (link layer)
9cfb16e8 IJ	22
	23	import sigrokdecode as srd
	24
	25	class Decoder(srd.Decoder):
	26	api_version = 1
	27	id = 'onewire_link'
	28	name = '1-Wire link layer'
e7720d6c	29	longname = '1-Wire serial communication bus (link layer)'
9cfb16e8 IJ	30	desc = 'Bidirectional, half-duplex, asynchronous serial bus.'
	31	license = 'gplv2+'
	32	inputs = ['logic']
	33	outputs = ['onewire_link']
	34	probes = [
3f302d51	35	{'id': 'owr', 'name': 'OWR', 'desc': '1-Wire signal line'},
9cfb16e8 IJ	36	]
9cfb16e8 IJ	37	optional_probes = [
3f302d51	38	{'id': 'pwr', 'name': 'PWR', 'desc': '1-Wire power supply pin'},
9cfb16e8 IJ	39	]
9cfb16e8 IJ	40	options = {
e7720d6c UH	41	'overdrive': ['Overdrive', 1],
	42	# Time options (specified in number of samplerate periods):
	43	'cnt_normal_bit': ['Normal mode sample bit time', 0],
	44	'cnt_normal_slot': ['Normal mode data slot time', 0],
	45	'cnt_normal_presence': ['Normal mode sample presence time', 0],
	46	'cnt_normal_reset': ['Normal mode reset time', 0],
	47	'cnt_overdrive_bit': ['Overdrive mode sample bit time', 0],
	48	'cnt_overdrive_slot': ['Overdrive mode data slot time', 0],
	49	'cnt_overdrive_presence': ['Overdrive mode sample presence time', 0],
	50	'cnt_overdrive_reset': ['Overdrive mode reset time', 0],
9cfb16e8 IJ	51	}
9cfb16e8 IJ	52	annotations = [
3f302d51 UH	53	['Text', 'Human-readable text'],
3f302d51 UH	54	['Warnings', 'Human-readable warnings'],
9cfb16e8 IJ	55	]
	56
	57	def __init__(self, **kwargs):
9cfb16e8	58	self.samplenum = 0
e7720d6c	59	self.state = 'WAIT FOR FALLING EDGE'
9cfb16e8	60	self.present = 0
e7720d6c	61	self.bit = 0
99f5f3b5 IJ	62	self.bit_cnt = 0
99f5f3b5 IJ	63	self.command = 0
9cfb16e8	64	self.overdrive = 0
e7720d6c UH	65	self.fall = 0
e7720d6c UH	66	self.rise = 0
9cfb16e8 IJ	67
	68	def start(self, metadata):
	69	self.out_proto = self.add(srd.OUTPUT_PROTO, 'onewire_link')
e7720d6c	70	self.out_ann = self.add(srd.OUTPUT_ANN, 'onewire_link')
9cfb16e8	71
9cfb16e8	72	self.samplerate = metadata['samplerate']
e7720d6c UH	73
	74	# Check if samplerate is appropriate.
	75	if self.options['overdrive']:
e7720d6c	76	if self.samplerate < 2000000:
3f302d51	77	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	78	['ERROR: Sampling rate is too low. Must be above 2MHz ' +
	79	'for proper overdrive mode decoding.']])
	80	elif self.samplerate < 5000000:
3f302d51	81	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	82	['WARNING: Sampling rate is suggested to be above 5MHz ' +
e7720d6c UH	83	'for proper overdrive mode decoding.']])
9cfb16e8	84	else:
e7720d6c	85	if self.samplerate < 400000:
3f302d51	86	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	87	['ERROR: Sampling rate is too low. Must be above ' +
e7720d6c UH	88	'400kHz for proper normal mode decoding.']])
9cfb16e8	89	elif (self.samplerate < 1000000):
3f302d51	90	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	91	['WARNING: Sampling rate is suggested to be above ' +
e7720d6c UH	92	'1MHz for proper normal mode decoding.']])
9cfb16e8	93
e7720d6c UH	94	# The default 1-Wire time base is 30us. This is used to calculate
	95	# sampling times.
	96	samplerate = float(self.samplerate)
	97	if self.options['cnt_normal_bit']:
9cfb16e8 IJ	98	self.cnt_normal_bit = self.options['cnt_normal_bit']
9cfb16e8 IJ	99	else:
e7720d6c UH	100	self.cnt_normal_bit = int(samplerate * 0.000015) - 1 # 15ns
e7720d6c UH	101	if self.options['cnt_normal_slot']:
671cc300 IJ	102	self.cnt_normal_slot = self.options['cnt_normal_slot']
671cc300 IJ	103	else:
e7720d6c UH	104	self.cnt_normal_slot = int(samplerate * 0.000060) - 1 # 60ns
e7720d6c UH	105	if self.options['cnt_normal_presence']:
9cfb16e8 IJ	106	self.cnt_normal_presence = self.options['cnt_normal_presence']
9cfb16e8 IJ	107	else:
e7720d6c UH	108	self.cnt_normal_presence = int(samplerate * 0.000075) - 1 # 75ns
e7720d6c UH	109	if self.options['cnt_normal_reset']:
9cfb16e8 IJ	110	self.cnt_normal_reset = self.options['cnt_normal_reset']
9cfb16e8 IJ	111	else:
e7720d6c UH	112	self.cnt_normal_reset = int(samplerate * 0.000480) - 1 # 480ns
e7720d6c UH	113	if self.options['cnt_overdrive_bit']:
9cfb16e8 IJ	114	self.cnt_overdrive_bit = self.options['cnt_overdrive_bit']
9cfb16e8 IJ	115	else:
e7720d6c UH	116	self.cnt_overdrive_bit = int(samplerate * 0.000002) - 1 # 2ns
e7720d6c UH	117	if self.options['cnt_overdrive_slot']:
671cc300 IJ	118	self.cnt_overdrive_slot = self.options['cnt_overdrive_slot']
671cc300 IJ	119	else:
e7720d6c UH	120	self.cnt_overdrive_slot = int(samplerate * 0.0000073) - 1 # 6ns+1.3ns
e7720d6c UH	121	if self.options['cnt_overdrive_presence']:
9cfb16e8 IJ	122	self.cnt_overdrive_presence = self.options['cnt_overdrive_presence']
9cfb16e8 IJ	123	else:
e7720d6c UH	124	self.cnt_overdrive_presence = int(samplerate * 0.000010) - 1 # 10ns
e7720d6c UH	125	if self.options['cnt_overdrive_reset']:
9cfb16e8 IJ	126	self.cnt_overdrive_reset = self.options['cnt_overdrive_reset']
9cfb16e8 IJ	127	else:
e7720d6c	128	self.cnt_overdrive_reset = int(samplerate * 0.000048) - 1 # 48ns
9cfb16e8	129
e7720d6c UH	130	# Organize values into lists.
e7720d6c UH	131	self.cnt_bit = [self.cnt_normal_bit, self.cnt_overdrive_bit]
9cfb16e8	132	self.cnt_presence = [self.cnt_normal_presence, self.cnt_overdrive_presence]
e7720d6c UH	133	self.cnt_reset = [self.cnt_normal_reset, self.cnt_overdrive_reset]
	134	self.cnt_slot = [self.cnt_normal_slot, self.cnt_overdrive_slot]
	135
	136	# Check if sample times are in the allowed range.
	137
	138	time_min = float(self.cnt_normal_bit) / self.samplerate
	139	time_max = float(self.cnt_normal_bit + 1) / self.samplerate
	140	if (time_min < 0.000005) or (time_max > 0.000015):
3f302d51	141	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	142	['WARNING: The normal mode data sample time interval ' +
	143	'(%2.1fus-%2.1fus) should be inside (5.0us, 15.0us).'
	144	% (time_min * 1000000, time_max * 1000000)]])
	145
	146	time_min = float(self.cnt_normal_presence) / self.samplerate
	147	time_max = float(self.cnt_normal_presence + 1) / self.samplerate
	148	if (time_min < 0.0000681) or (time_max > 0.000075):
3f302d51	149	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	150	['WARNING: The normal mode presence sample time interval ' +
	151	'(%2.1fus-%2.1fus) should be inside (68.1us, 75.0us).'
	152	% (time_min * 1000000, time_max * 1000000)]])
	153
	154	time_min = float(self.cnt_overdrive_bit) / self.samplerate
	155	time_max = float(self.cnt_overdrive_bit + 1) / self.samplerate
	156	if (time_min < 0.000001) or (time_max > 0.000002):
3f302d51	157	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	158	['WARNING: The overdrive mode data sample time interval ' +
	159	'(%2.1fus-%2.1fus) should be inside (1.0us, 2.0us).'
	160	% (time_min * 1000000, time_max * 1000000)]])
	161
	162	time_min = float(self.cnt_overdrive_presence) / self.samplerate
	163	time_max = float(self.cnt_overdrive_presence + 1) / self.samplerate
	164	if (time_min < 0.0000073) or (time_max > 0.000010):
3f302d51	165	self.put(0, 0, self.out_ann, [1,
e7720d6c UH	166	['WARNING: The overdrive mode presence sample time interval ' +
	167	'(%2.1fus-%2.1fus) should be inside (7.3us, 10.0us).'
	168	% (time_min1000000, time_max1000000)]])
9cfb16e8 IJ	169
	170	def report(self):
	171	pass
	172
	173	def decode(self, ss, es, data):
	174	for (self.samplenum, (owr, pwr)) in data:
9cfb16e8 IJ	175	# State machine.
	176	if self.state == 'WAIT FOR FALLING EDGE':
	177	# The start of a cycle is a falling edge.
48b59746 UH	178	if owr != 0:
	179	continue
	180	# Save the sample number for the falling edge.
	181	self.fall = self.samplenum
	182	# Go to waiting for sample time.
	183	self.state = 'WAIT FOR DATA SAMPLE'
9cfb16e8	184	elif self.state == 'WAIT FOR DATA SAMPLE':
e7720d6c UH	185	# Sample data bit.
	186	t = self.samplenum - self.fall
	187	if t == self.cnt_bit[self.overdrive]:
	188	self.bit = owr
671cc300 IJ	189	self.state = 'WAIT FOR DATA SLOT END'
671cc300 IJ	190	elif self.state == 'WAIT FOR DATA SLOT END':
e7720d6c UH	191	# A data slot ends in a recovery period, otherwise, this is
	192	# probably a reset.
	193	t = self.samplenum - self.fall
48b59746 UH	194	if t != self.cnt_slot[self.overdrive]:
	195	continue
	196
	197	if owr == 0:
	198	# This seems to be a reset slot, wait for its end.
	199	self.state = 'WAIT FOR RISING EDGE'
	200	continue
	201
	202	self.put(self.fall, self.samplenum, self.out_ann,
3f302d51	203	[0, ['Bit: %d' % self.bit]])
48b59746 UH	204	self.put(self.fall, self.samplenum, self.out_proto,
48b59746 UH	205	['BIT', self.bit])
e7720d6c	206
48b59746 UH	207	# Checking the first command to see if overdrive mode
	208	# should be entered.
	209	if self.bit_cnt <= 8:
	210	self.command \|= (self.bit << self.bit_cnt)
	211	elif self.bit_cnt == 8 and self.command in [0x3c, 0x69]:
	212	self.put(self.fall, self.cnt_bit[self.overdrive],
3f302d51	213	self.out_ann, [0, ['Entering overdrive mode']])
48b59746 UH	214	# Increment the bit counter.
	215	self.bit_cnt += 1
	216	# Wait for next slot.
	217	self.state = 'WAIT FOR FALLING EDGE'
9cfb16e8 IJ	218	elif self.state == 'WAIT FOR RISING EDGE':
9cfb16e8 IJ	219	# The end of a cycle is a rising edge.
48b59746 UH	220	if owr != 1:
	221	continue
	222
	223	# Check if this was a reset cycle.
	224	t = self.samplenum - self.fall
	225	if t > self.cnt_normal_reset:
	226	# Save the sample number for the falling edge.
	227	self.rise = self.samplenum
	228	self.state = 'WAIT FOR PRESENCE DETECT'
	229	# Exit overdrive mode.
	230	if self.overdrive:
	231	self.put(self.fall, self.cnt_bit[self.overdrive],
3f302d51	232	self.out_ann, [0, ['Exiting overdrive mode']])
48b59746 UH	233	self.overdrive = 0
	234	# Clear command bit counter and data register.
	235	self.bit_cnt = 0
	236	self.command = 0
	237	elif (t > self.cnt_overdrive_reset) and self.overdrive:
	238	# Save the sample number for the falling edge.
	239	self.rise = self.samplenum
	240	self.state = "WAIT FOR PRESENCE DETECT"
	241	# Otherwise this is assumed to be a data bit.
	242	else:
	243	self.state = "WAIT FOR FALLING EDGE"
9cfb16e8	244	elif self.state == 'WAIT FOR PRESENCE DETECT':
e7720d6c UH	245	# Sample presence status.
	246	t = self.samplenum - self.rise
	247	if t == self.cnt_presence[self.overdrive]:
671cc300 IJ	248	self.present = owr
	249	self.state = 'WAIT FOR RESET SLOT END'
	250	elif self.state == 'WAIT FOR RESET SLOT END':
48b59746	251	# A reset slot ends in a long recovery period.
e7720d6c	252	t = self.samplenum - self.rise
48b59746 UH	253	if t != self.cnt_reset[self.overdrive]:
	254	continue
	255
	256	if owr == 0:
	257	# This seems to be a reset slot, wait for its end.
	258	self.state = 'WAIT FOR RISING EDGE'
	259	continue
	260
	261	self.put(self.fall, self.samplenum, self.out_ann,
3f302d51 UH	262	[0, ['Reset/presence: %s'
3f302d51 UH	263	% ('false' if self.present else 'true')]])
48b59746 UH	264	self.put(self.fall, self.samplenum, self.out_proto,
	265	['RESET/PRESENCE', not self.present])
	266	# Wait for next slot.
	267	self.state = 'WAIT FOR FALLING EDGE'
9cfb16e8	268	else:
e7720d6c	269	raise Exception('Invalid state: %s' % self.state)