parallel: rephrase handling of data lines, symbolic upper bound

[libsigrokdecode.git] / decoders / parallel / pd.py

##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2013-2016 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, see <http://www.gnu.org/licenses/>.
##

import sigrokdecode as srd
from common.srdhelper import bitpack

'''
OUTPUT_PYTHON format:

Packet:
[<ptype>, <pdata>]

<ptype>, <pdata>
 - 'ITEM', [<item>, <itembitsize>]
 - 'WORD', [<word>, <wordbitsize>, <worditemcount>]

<item>:
 - A single item (a number). It can be of arbitrary size. The max. number
   of bits in this item is specified in <itembitsize>.

<itembitsize>:
 - The size of an item (in bits). For a 4-bit parallel bus this is 4,
   for a 16-bit parallel bus this is 16, and so on.

<word>:
 - A single word (a number). It can be of arbitrary size. The max. number
   of bits in this word is specified in <wordbitsize>. The (exact) number
   of items in this word is specified in <worditemcount>.

<wordbitsize>:
 - The size of a word (in bits). For a 2-item word with 8-bit items
   <wordbitsize> is 16, for a 3-item word with 4-bit items <wordbitsize>
   is 12, and so on.

<worditemcount>:
 - The size of a word (in number of items). For a 4-item word (no matter
   how many bits each item consists of) <worditemcount> is 4, for a 7-item
   word <worditemcount> is 7, and so on.
'''

NUM_CHANNELS = 8

class Pin:
    CLOCK = 0
    DATA_0 = CLOCK + 1
    DATA_N = DATA_0 + NUM_CHANNELS

class Ann:
    ITEM, WORD = range(2)

class ChannelError(Exception):
    pass

class Decoder(srd.Decoder):
    api_version = 3
    id = 'parallel'
    name = 'Parallel'
    longname = 'Parallel sync bus'
    desc = 'Generic parallel synchronous bus.'
    license = 'gplv2+'
    inputs = ['logic']
    outputs = ['parallel']
    tags = ['Util']
    optional_channels = tuple(
        [{'id': 'clk', 'name': 'CLK', 'desc': 'Clock line'}] +
        [
            {'id': 'd%d' % i, 'name': 'D%d' % i, 'desc': 'Data line %d' % i}
            for i in range(NUM_CHANNELS)
        ]
    )
    options = (
        {'id': 'clock_edge', 'desc': 'Clock edge to sample on',
            'default': 'rising', 'values': ('rising', 'falling')},
        {'id': 'wordsize', 'desc': 'Data wordsize (# bus cycles)',
            'default': 0},
        {'id': 'endianness', 'desc': 'Data endianness',
            'default': 'little', 'values': ('little', 'big')},
    )
    annotations = (
        ('item', 'Item'),
        ('word', 'Word'),
    )
    annotation_rows = (
        ('items', 'Items', (Ann.ITEM,)),
        ('words', 'Words', (Ann.WORD,)),
    )

    def __init__(self):
        self.reset()

    def reset(self):
        self.items = []
        self.saved_item = None
        self.ss_item = self.es_item = None
        self.saved_word = None
        self.ss_word = self.es_word = None
        self.first = True

    def start(self):
        self.out_python = self.register(srd.OUTPUT_PYTHON)
        self.out_ann = self.register(srd.OUTPUT_ANN)

    def putpb(self, data):
        self.put(self.ss_item, self.es_item, self.out_python, data)

    def putb(self, data):
        self.put(self.ss_item, self.es_item, self.out_ann, data)

    def putpw(self, data):
        self.put(self.ss_word, self.es_word, self.out_python, data)

    def putw(self, data):
        self.put(self.ss_word, self.es_word, self.out_ann, data)

    def handle_bits(self, item, used_pins):

        # If a word was previously accumulated, then emit its annotation
        # now after its end samplenumber became available.
        if self.saved_word is not None:
            if self.options['wordsize'] > 0:
                self.es_word = self.samplenum
                self.putw([Ann.WORD, [self.fmt_word.format(self.saved_word)]])
                self.putpw(['WORD', self.saved_word])
            self.saved_word = None

        # Defer annotations for individual items until the next sample
        # is taken, and the previous sample's end samplenumber has
        # become available.
        if self.first:
            # Save the start sample and item for later (no output yet).
            self.ss_item = self.samplenum
            self.first = False
            self.saved_item = item
        else:
            # Output the saved item (from the last CLK edge to the current).
            self.es_item = self.samplenum
            self.putpb(['ITEM', self.saved_item])
            self.putb([Ann.ITEM, [self.fmt_item.format(self.saved_item)]])
            self.ss_item = self.samplenum
            self.saved_item = item

        # Get as many items as the configured wordsize specifies.
        if not self.items:
            self.ss_word = self.samplenum
        self.items.append(item)
        ws = self.options['wordsize']
        if len(self.items) < ws:
            return

        # Collect words and prepare annotation details, but defer emission
        # until the end samplenumber becomes available.
        endian = self.options['endianness']
        if endian == 'big':
            self.items.reverse()
        word = sum([self.items[i] << (i * used_pins) for i in range(ws)])
        self.saved_word = word
        self.items = []

    def decode(self):
        # Determine which (optional) channels have input data. Insist in
        # a non-empty input data set. Cope with sparse connection maps.
        # Store enough state to later "compress" sampled input data.
        data_indices = [
            idx if self.has_channel(idx) else None
            for idx in range(Pin.DATA_0, Pin.DATA_N)
        ]
        has_data = [idx for idx in data_indices if idx is not None]
        if not has_data:
            raise ChannelError('Need at least one data channel.')
        max_connected = max(has_data)

        # Pre-determine which input data to strip off, the width of
        # individual items and multiplexed words, as well as format
        # strings here. This simplifies call sites which run in tight
        # loops later.
        upper_data_bound = max_connected + 1
        num_item_bits = upper_data_bound - Pin.DATA_0
        num_word_items = self.options['wordsize']
        num_word_bits = num_item_bits * num_word_items
        num_digits = (num_item_bits + 4 - 1) // 4
        self.fmt_item = "{{:0{}x}}".format(num_digits)
        num_digits = (num_word_bits + 4 - 1) // 4
        self.fmt_word = "{{:0{}x}}".format(num_digits)

        # Determine .wait() conditions, depending on the presence of a
        # clock signal. Either inspect samples on the configured edge of
        # the clock, or inspect samples upon ANY edge of ANY of the pins
        # which provide input data.
        has_clock = self.has_channel(Pin.CLOCK)
        if has_clock:
            edge = self.options['clock_edge'][0]
            conds = [{Pin.CLOCK: edge}]
        else:
            conds = [{idx: 'e'} for idx in has_data]

        # Keep processing the input stream. Assume "always zero" for
        # not-connected input lines. Pass data bits (all inputs except
        # clock) to the handle_bits() method.
        while True:
            pins = self.wait(conds)
            data_bits = [0 if idx is None else pins[idx] for idx in data_indices]
            data_bits = data_bits[:num_item_bits]
            item = bitpack(data_bits)
            self.handle_bits(item, num_item_bits)