mirror of
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132 lines
4.1 KiB
Python
132 lines
4.1 KiB
Python
##
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## This file is part of the libsigrokdecode project.
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##
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## Copyright (C) 2019-2020 Philip Åkesson <philip.akesson@gmail.com>
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##
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## This program is free software; you can redistribute it and/or modify
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## it under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 2 of the License, or
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## (at your option) any later version.
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##
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## This program is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU General Public License for more details.
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##
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## You should have received a copy of the GNU General Public License
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## along with this program; if not, see <http://www.gnu.org/licenses/>.
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##
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from common.srdhelper import bitpack
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import sigrokdecode as srd
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class SamplerateError(Exception):
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pass
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class Pin:
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SDQ, = range(1)
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class Ann:
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BIT, BYTE, BREAK, = range(3)
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class Decoder(srd.Decoder):
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api_version = 3
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id = 'sdq'
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name = 'SDQ'
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longname = 'Texas Instruments SDQ'
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desc = 'Texas Instruments SDQ. The SDQ protocol is also used by Apple.'
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license = 'gplv2+'
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inputs = ['logic']
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outputs = []
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tags = ['Embedded/industrial']
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channels = (
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{'id': 'sdq', 'name': 'SDQ', 'desc': 'Single wire SDQ data line.', 'idn':'dec_sdq_chan_sdq'},
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)
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options = (
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{'id': 'bitrate', 'desc': 'Bit rate', 'default': 98425, 'idn':'dec_sdq_opt_bitrate'},
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)
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annotations = (
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('bit', 'Bit'),
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('byte', 'Byte'),
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('break', 'Break'),
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)
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annotation_rows = (
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('bits', 'Bits', (Ann.BIT,)),
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('bytes', 'Bytes', (Ann.BYTE,)),
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('breaks', 'Breaks', (Ann.BREAK,)),
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)
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def puts(self, data):
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self.put(self.startsample, self.samplenum, self.out_ann, data)
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def putetu(self, data):
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self.put(self.startsample, self.startsample + int(self.bit_width), self.out_ann, data)
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def putbetu(self, data):
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self.put(self.bytepos, self.startsample + int(self.bit_width), self.out_ann, data)
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def __init__(self):
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self.reset()
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def reset(self):
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self.samplerate = None
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self.startsample = 0
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self.bits = []
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self.bytepos = 0
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def start(self):
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self.out_ann = self.register(srd.OUTPUT_ANN)
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def metadata(self, key, value):
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if key == srd.SRD_CONF_SAMPLERATE:
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self.samplerate = value
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def handle_bit(self, bit):
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self.bits.append(bit)
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self.putetu([Ann.BIT, [
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'Bit: {:d}'.format(bit),
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'{:d}'.format(bit),
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]])
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if len(self.bits) == 8:
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byte = bitpack(self.bits)
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self.putbetu([Ann.BYTE, [
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'Byte: 0x{:02x}'.format(byte),
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'0x{:02x}'.format(byte),
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]])
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self.bits = []
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self.bytepos = 0
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def handle_break(self):
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self.puts([Ann.BREAK, ['Break', 'BR']])
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self.bits = []
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self.startsample = self.samplenum
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self.bytepos = 0
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def decode(self):
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if not self.samplerate:
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raise SamplerateError('Cannot decode without samplerate.')
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self.bit_width = float(self.samplerate) / float(self.options['bitrate'])
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self.half_bit_width = self.bit_width / 2.0
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# BREAK if the line is low for longer than this.
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break_threshold = self.bit_width * 1.2
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# Wait until the line is high before inspecting input data.
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sdq, = self.wait({Pin.SDQ: 'h'})
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while True:
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# Get the length of a low pulse (falling to rising edge).
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sdq, = self.wait({Pin.SDQ: 'f'})
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self.startsample = self.samplenum
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if self.bytepos == 0:
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self.bytepos = self.samplenum
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sdq, = self.wait({Pin.SDQ: 'r'})
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# Check for 0 or 1 data bits, or the BREAK symbol.
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delta = self.samplenum - self.startsample
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if delta > break_threshold:
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self.handle_break()
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elif delta > self.half_bit_width:
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self.handle_bit(0)
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else:
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self.handle_bit(1)
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