##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 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
##

import sigrokdecode as srd

class Decoder(srd.Decoder):
    api_version = 1
    id = 'guess_bitrate'
    name = 'Guess bitrate'
    longname = 'Guess bitrate/baudrate'
    desc = 'Guess the bitrate/baudrate of a UART (or other) protocol.'
    license = 'gplv2+'
    inputs = ['logic']
    outputs = ['guess_bitrate']
    probes = [
        {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
    ]
    optional_probes = []
    options = {}
    annotations = [
        ['bitrate', 'Bitrate / baudrate'],
    ]

    def putx(self, data):
        self.put(self.ss_edge, self.samplenum, self.out_ann, data)

    def __init__(self, **kwargs):
        self.olddata = None
        self.ss_edge = None
        self.first_transition = True
        self.bitwidth = None

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

    def metadata(self, key, value):
        if key == srd.SRD_CONF_SAMPLERATE:
            self.samplerate = value;

    def decode(self, ss, es, data):
        if self.samplerate is None:
            raise Exception("Cannot decode without samplerate.")
        for (self.samplenum, pins) in data:

            data = pins[0]

            # Wait for any transition on the data line.
            if data == self.olddata:
                continue

            # Initialize first self.olddata with the first sample value.
            if self.olddata == None:
                self.olddata = data
                continue

            # Get the smallest distance between two transitions
            # and use that to calculate the bitrate/baudrate.
            if self.first_transition == True:
                self.ss_edge = self.samplenum
                self.first_transition = False
            else:
                b = self.samplenum - self.ss_edge
                if self.bitwidth == None or b < self.bitwidth:
                    self.bitwidth = b
                    bitrate = int(float(self.samplerate) / float(b))
                    self.putx([0, ['%d' % bitrate]])
                self.ss_edge = self.samplenum

            self.olddata = data