srd: nunchuk.py: Add some more URLs.

[libsigrokdecode.git] / decoders / srd_usb.py

##
## This file is part of the sigrok project.
##
## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
##
## 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
##

# USB Full-speed protocol decoder

# Full-speed usb singalling consists of two signal lines, both driven at 3.3V
# logic levels.  The signals are DP and DM, and normally operate in 
# differential mode.  
# The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K.
# A state SE0 is defined where DP=DM=0.  This common mode signal is used to
# signal a reset or end of packet.

# Data transmitted on the USB is encoded with NRZI.  A transision from J to K
# or vice-versa indicates a logic 0, while no transision indicates a logic 1.
# If 6 ones are transmitted consecutively, a zero is inserted to force a 
# transition.  This is known as bit stuffing.  Data is transferred at a rate 
# of 12Mbit/s.  The SE0 transmitted to signal an end-of-packet is two bit 
# intervals long.

import sigrok

class Sample():
    def __init__(self, data):
        self.data = data
    def probe(self, probe):
        s = ord(self.data[probe / 8]) & (1 << (probe % 8))
        return True if s else False

def sampleiter(data, unitsize):
    for i in range(0, len(data), unitsize):
        yield(Sample(data[i:i+unitsize]))

SE0, J, K, SE1 = 0, 1, 2, 3
syms = {
        (False, False): SE0,
        (True, False): J,
        (False, True): K,
        (True, True): SE1,
}

def bitstr_to_num(bitstr):
    if not bitstr: return 0
    l = list(bitstr)
    l.reverse()
    return int(''.join(l), 2)

def packet_decode(packet):
    pids = {'10000111':'OUT',  #Tokens
        '10010110':'IN',
        '10100101':'SOF',
        '10110100':'SETUP',
        '11000011':'DATA0',    #Data
        '11010010':'DATA1',
        '01001011':'ACK',      #Handshake
        '01011010':'NAK',
        '01111000':'STALL',
        '01101001':'NYET',
    }

    sync = packet[:8]
    pid = packet[8:16]
    pid = pids.get(pid, pid)
    #Remove CRC
    if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
        data = packet[16:-5]
        if pid == 'SOF':
            data = str(bitstr_to_num(data))
        else:
            dev = bitstr_to_num(data[:7])
            ep = bitstr_to_num(data[7:])
            data = "DEV %d EP %d" % (dev, ep)

    elif pid in ('DATA0', 'DATA1'):
        data = packet[16:-16]
        tmp = ""
        while data:
            tmp += "%02X " % bitstr_to_num(data[:8])
            data = data[8:]
        data = tmp
    else:
        data = packet[16:]

    if sync != "00000001":
        return "SYNC INVALID!"
    
    return pid + ' ' + data

class Decoder():
    name = 'USB'
    desc = 'Universal Serial Bus'
    longname = '...longname...'
    longdesc = '...longdesc...'
    author = 'Gareth McMullin'
    email = 'gareth@blacksphere.co.nz'
    license = 'gplv2+'
    inputs = ['logic']
    outputs = ['usb']
    # Probe names with a set of defaults
    probes = {'dp':0, 'dm':1}
    options = {}

    def __init__(self):
        self.probes = Decoder.probes.copy()

    def start(self, metadata):
        self.unitsize = metadata['unitsize']
        self.rate = metadata['samplerate']
        if self.rate < 48000000:
            raise Exception("Sample rate not sufficient for USB decoding")
        # initialise decoder state
        self.sym = J
        self.scount = 0
        self.packet = ''

    def decode(self, data):
        for sample in sampleiter(data['data'], self.unitsize):

            self.scount += 1

            sym = syms[sample.probe(self.probes['dp']), 
                        sample.probe(self.probes['dm'])] 
            if sym == self.sym:
                continue

            if self.scount == 1:
                # We ignore single sample width pulses. 
                # I sometimes get these with the OLS
                self.sym = sym
                self.scount = 0
                continue

            # how many bits since the last transition?
            if self.packet or self.sym != J:
                bitcount = (self.scount - 1) * 12000000 / self.rate
            else:
                bitcount = 0

            if self.sym == SE0:
                if bitcount == 1:
                    # End-Of-Packet
                    sigrok.put({"type":"usb", "data":self.packet, 
                                "display":packet_decode(self.packet)})
                else:
                     # Longer than EOP, assume reset
                    sigrok.put({"type":"usb", "display":"RESET"})
                self.scount = 0
                self.sym = sym
                self.packet = ''
                continue

            # Add bits to the packet string.
            self.packet += '1' * bitcount
            # Handle bit stuffing
            if bitcount < 6 and sym != SE0:
                self.packet += '0'
            elif bitcount > 6:
                sigrok.put({"type":"usb", "display":"BIT STUFF ERROR"})
            
            self.scount = 0
            self.sym = sym