##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2018 Mike Jagdis <mjagdis@eris-associates.co.uk>
##
## 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
##
import math
import sigrokdecode as srd
class SamplerateError(Exception):
pass
class Decoder(srd.Decoder):
api_version = 3
id = 'swim'
name = 'SWIM'
longname = 'STM8 SWIM bus'
desc = 'STM8 Single Wire Interface Module (SWIM) protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = []
tags = ['Debug/trace']
options = (
{'id': 'debug', 'desc': 'Debug', 'default': 'no', 'values': ('yes', 'no') },
)
channels = (
{'id': 'swim', 'name': 'SWIM', 'desc': 'SWIM data line'},
)
annotations = (
('bit', 'Bit'),
('enterseq', 'SWIM enter sequence'),
('start-host', 'Start bit (host)'),
('start-target', 'Start bit (target)'),
('parity', 'Parity bit'),
('ack', 'Acknowledgement'),
('nack', 'Negative acknowledgement'),
('byte-write', 'Byte write'),
('byte-read', 'Byte read'),
('cmd-unknown', 'Unknown SWIM command'),
('cmd', 'SWIM command'),
('bytes', 'Byte count'),
('address', 'Address'),
('data-write', 'Data write'),
('data-read', 'Data read'),
('debug', 'Debug'),
)
annotation_rows = (
('bits', 'Bits', (0,)),
('framing', 'Framing', (2, 3, 4, 5, 6, 7, 8)),
('protocol', 'Protocol', (1, 9, 10, 11, 12, 13, 14)),
('debug', 'Debug', (15,)),
)
binary = (
('tx', 'Dump of data written to target'),
('rx', 'Dump of data read from target'),
)
def __init__(self):
# SWIM clock for the target is normally HSI/2 where HSI is 8MHz +- 5%
# although the divisor can be removed by setting the SWIMCLK bit in
# the CLK_SWIMCCR register. There is no standard for the host so we
# will be generous and assume it is using an 8MHz +- 10% oscillator.
# We do not need to be accurate. We just need to avoid treating enter
# sequence pulses as bits. A synchronization frame will cause this
# to be adjusted.
self.HSI = 8000000
self.HSI_min = self.HSI * 0.9
self.HSI_max = self.HSI * 1.1
self.swim_clock = self.HSI_min / 2
self.eseq_edge = [[-1, None], [-1, None]]
self.eseq_pairnum = 0
self.eseq_pairstart = None
self.reset()
def reset(self):
self.bit_edge = [[-1, None], [-1, None]]
self.bit_maxlen = -1
self.bitseq_len = 0
self.bitseq_end = None
self.proto_state = 'CMD'
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
def adjust_timings(self):
# A low-speed bit is 22 SWIM clocks long.
# There are options to shorten bits to 10 clocks or use HSI rather
# than HSI/2 as the SWIM clock but the longest valid bit should be no
# more than this many samples. This does not need to be accurate.
# It exists simply to prevent bits extending unecessarily far into
# trailing bus-idle periods. This will be adjusted every time we see
# a synchronization frame or start bit in order to show idle periods
# as accurately as possible.
self.bit_reflen = math.ceil(self.samplerate * 22 / self.swim_clock)
def start(self):
self.out_ann = self.register(srd.OUTPUT_ANN)
self.out_binary = self.register(srd.OUTPUT_BINARY)
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
# A synchronization frame is a low that lasts for more than 64 but no
# more than 128 SWIM clock periods based on the standard SWIM clock.
# Note: we also allow for the possibility that the SWIM clock divisor
# has been disabled here.
self.sync_reflen_min = math.floor(self.samplerate * 64 / self.HSI_max)
self.sync_reflen_max = math.ceil(self.samplerate * 128 / (self.HSI_min / 2))
self.debug = True if self.options['debug'] == 'yes' else False
# The SWIM entry sequence is 4 pulses at 2kHz followed by 4 at 1kHz.
self.eseq_reflen = math.ceil(self.samplerate / 2048)
self.adjust_timings()
def protocol(self):
if self.proto_state == 'CMD':
# Command
if self.bitseq_value == 0x00:
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [10, ['system reset', 'SRST', '!']])
elif self.bitseq_value == 0x01:
self.proto_state = 'N'
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [10, ['read on-the-fly', 'ROTF', 'r']])
elif self.bitseq_value == 0x02:
self.proto_state = 'N'
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [10, ['write on-the-fly', 'WOTF', 'w']])
else:
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [9, ['unknown', 'UNK']])
elif self.proto_state == 'N':
# Number of bytes
self.proto_byte_count = self.bitseq_value
self.proto_state = '@E'
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [11, ['byte count 0x%02x' % self.bitseq_value, 'bytes 0x%02x' % self.bitseq_value, '0x%02x' % self.bitseq_value, '%02x' % self.bitseq_value, '%x' % self.bitseq_value]])
elif self.proto_state == '@E':
# Address byte 1
self.proto_addr = self.bitseq_value
self.proto_addr_start = self.bitseq_start
self.proto_state = '@H'
elif self.proto_state == '@H':
# Address byte 2
self.proto_addr = (self.proto_addr << 8) | self.bitseq_value
self.proto_state = '@L'
elif self.proto_state == '@L':
# Address byte 3
self.proto_addr = (self.proto_addr << 8) | self.bitseq_value
self.proto_state = 'D'
self.put(self.proto_addr_start, self.bitseq_end, self.out_ann, [12, ['address 0x%06x' % self.proto_addr, 'addr 0x%06x' % self.proto_addr, '0x%06x' % self.proto_addr, '%06x' %self.proto_addr, '%x' % self.proto_addr]])
else:
if self.proto_byte_count > 0:
self.proto_byte_count -= 1
if self.proto_byte_count == 0:
self.proto_state = 'CMD'
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [13 + self.bitseq_dir, ['0x%02x' % self.bitseq_value, '%02x' % self.bitseq_value, '%x' % self.bitseq_value]])
self.put(self.bitseq_start, self.bitseq_end, self.out_binary, [0 + self.bitseq_dir, bytes([self.bitseq_value])])
if self.debug:
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [15, ['%d more' % self.proto_byte_count, '%d' % self.proto_byte_count]])
def bitseq(self, bitstart, bitend, bit):
if self.bitseq_len == 0:
# Looking for start of a bit sequence (command or byte).
self.bit_reflen = bitend - bitstart
self.bitseq_value = 0
self.bitseq_dir = bit
self.bitseq_len = 1
self.put(bitstart, bitend, self.out_ann, [2 + self.bitseq_dir, ['start', 's']])
elif (self.proto_state == 'CMD' and self.bitseq_len == 4) or (self.proto_state != 'CMD' and self.bitseq_len == 9):
# Parity bit
self.bitseq_end = bitstart
self.bitseq_len += 1
self.put(bitstart, bitend, self.out_ann, [4, ['parity', 'par', 'p']])
# The start bit is not data but was used for parity calculation.
self.bitseq_value &= 0xff
self.put(self.bitseq_start, self.bitseq_end, self.out_ann, [7 + self.bitseq_dir, ['0x%02x' % self.bitseq_value, '%02x' % self.bitseq_value, '%x' % self.bitseq_value]])
elif (self.proto_state == 'CMD' and self.bitseq_len == 5) or (self.proto_state != 'CMD' and self.bitseq_len == 10):
# ACK/NACK bit.
if bit:
self.put(bitstart, bitend, self.out_ann, [5, ['ack', 'a']])
else:
self.put(bitstart, bitend, self.out_ann, [6, ['nack', 'n']])
# We only pass data that was ack'd up the stack.
if bit:
self.protocol()
self.bitseq_len = 0
else:
if self.bitseq_len == 1:
self.bitseq_start = bitstart
self.bitseq_value = (self.bitseq_value << 1) | bit
self.bitseq_len += 1
def bit(self, start, mid, end):
if mid - start >= end - mid:
self.put(start, end, self.out_ann, [0, ['0']])
bit = 0
else:
self.put(start, end, self.out_ann, [0, ['1']])
bit = 1
self.bitseq(start, end, bit)
def detect_synchronize_frame(self, start, end):
# Strictly speaking, synchronization frames are only recognised when
# SWIM is active. A falling edge on reset disables SWIM and an enter
# sequence is needed to re-enable it. However we do not want to be
# reliant on seeing the NRST pin just for that and we also want to be
# able to decode SWIM even if we just sample parts of the dialogue.
# For this reason we limit ourselves to only recognizing
# synchronization frames that have believable lengths based on our
# knowledge of the range of possible SWIM clocks.
if self.samplenum - self.eseq_edge[1][1] >= self.sync_reflen_min and self.samplenum - self.eseq_edge[1][1] <= self.sync_reflen_max:
self.put(self.eseq_edge[1][1], self.samplenum, self.out_ann, [1, ['synchronization frame', 'synchronization', 'sync', 's']])
# A low that lasts for more than 64 SWIM clock periods causes a
# reset of the SWIM communication state machine and will switch
# the SWIM to low-speed mode (SWIM_CSR.HS is cleared).
self.reset()
# The low SHOULD last 128 SWIM clocks. This is used to
# resynchronize in order to allow for variation in the frequency
# of the internal RC oscillator.
self.swim_clock = 128 * (self.samplerate / (self.samplenum - self.eseq_edge[1][1]))
self.adjust_timings()
def eseq_potential_start(self, start, end):
self.eseq_pairstart = start
self.eseq_reflen = end - start
self.eseq_pairnum = 1
def detect_enter_sequence(self, start, end):
# According to the spec the enter sequence is four pulses at 2kHz
# followed by four at 1kHz. We do not check the frequency but simply
# check the lengths of successive pulses against the first. This means
# we have no need to account for the accuracy (or lack of) of the
# host's oscillator.
if self.eseq_pairnum == 0 or abs(self.eseq_reflen - (end - start)) > 2:
self.eseq_potential_start(start, end)
elif self.eseq_pairnum < 4:
# The next three pulses should be the same length as the first.
self.eseq_pairnum += 1
if self.eseq_pairnum == 4:
self.eseq_reflen /= 2
else:
# The final four pulses should each be half the length of the
# initial pair. Again, a mismatch causes us to reset and use the
# current pulse as a new potential enter sequence start.
self.eseq_pairnum += 1
if self.eseq_pairnum == 8:
# Four matching pulses followed by four more that match each
# other but are half the length of the first 4. SWIM is active!
self.put(self.eseq_pairstart, end, self.out_ann, [1, ['enter sequence', 'enter seq', 'enter', 'ent', 'e']])
self.eseq_pairnum = 0
def decode(self):
while True:
if self.bit_maxlen >= 0:
(swim,) = self.wait()
self.bit_maxlen -= 1
else:
(swim,) = self.wait({0: 'e'})
if swim != self.eseq_edge[1][0]:
if swim == 1 and self.eseq_edge[1][1] is not None:
self.detect_synchronize_frame(self.eseq_edge[1][1], self.samplenum)
if self.eseq_edge[0][1] is not None:
self.detect_enter_sequence(self.eseq_edge[0][1], self.samplenum)
self.eseq_edge.pop(0)
self.eseq_edge.append([swim, self.samplenum])
if (swim != self.bit_edge[1][0] and (swim != 1 or self.bit_edge[1][0] != -1)) or self.bit_maxlen == 0:
if self.bit_maxlen == 0 and self.bit_edge[1][0] == 1:
swim = -1
if self.bit_edge[1][0] != 0 and swim == 0:
self.bit_maxlen = self.bit_reflen
if self.bit_edge[0][0] == 0 and self.bit_edge[1][0] == 1 and self.samplenum - self.bit_edge[0][1] <= self.bit_reflen + 2:
self.bit(self.bit_edge[0][1], self.bit_edge[1][1], self.samplenum)
self.bit_edge.pop(0)
self.bit_edge.append([swim, self.samplenum])