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##
## 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 (low-speed and full-speed) protocol decoder
import sigrokdecode as srd
# Full-speed symbols (used as states of our state machine, too).
# Note: Low-speed J and K are inverted compared to the full-speed J and K!
syms = {
# (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'J',
(0, 1): 'K',
(1, 1): 'SE1',
}
# Packet IDs (PIDs).
# The first 4 bits are the 'packet type' field, the last 4 bits are the
# 'check field' (each bit in the check field must be the inverse of the resp.
# bit in the 'packet type' field; if not, that's a 'PID error').
# For the 4-bit strings, the left-most '1' or '0' is the LSB, i.e. it's sent
# to the bus first.
pids = {
# Tokens
'10000111': ['OUT', 'Address & EP number in host-to-function transaction'],
'10010110': ['IN', 'Address & EP number in function-to-host transaction'],
'10100101': ['SOF', 'Start-Of-Frame marker & frame number'],
'10110100': ['SETUP', 'Address & EP number in host-to-function transaction for SETUP to a control pipe'],
# Data
# Note: DATA2 and MDATA are HS-only.
'11000011': ['DATA0', 'Data packet PID even'],
'11010010': ['DATA1', 'Data packet PID odd'],
'11100001': ['DATA2', 'Data packet PID HS, high bandwidth isosynchronous transaction in a microframe'],
'11110000': ['MDATA', 'Data packet PID HS for split and high-bandwidth isosynchronous transactions'],
# Handshake
'01001011': ['ACK', 'Receiver accepts error-free packet'],
'01011010': ['NAK', 'Receiver cannot accept or transmitter cannot send'],
'01111000': ['STALL', 'EP halted or control pipe request unsupported'],
'01101001': ['NYET', 'No response yet from receiver'],
# Special
'00111100': ['PRE', 'Host-issued preamble; enables downstream bus traffic to low-speed devices'],
'00111100': ['ERR', 'Split transaction error handshake'],
'00011110': ['SPLIT', 'HS split transaction token'],
'00101101': ['PING', 'HS flow control probe for a bulk/control EP'],
'00001111': ['Reserved', 'Reserved PID'],
}
def get_sym(signalling, dp, dm):
# Note: Low-speed J and K are inverted compared to the full-speed J and K!
if signalling == 'low-speed':
s = syms[dp, dm]
if s == 'J':
return 'K'
elif s == 'K':
return 'J'
else:
return s
elif signalling == 'full-speed':
return syms[dp, dm]
def bitstr_to_num(bitstr):
if not bitstr:
return 0
l = list(bitstr)
l.reverse()
return int(''.join(l), 2)
def packet_decode(packet):
sync = packet[:8]
pid = packet[8:16]
pid = pids.get(pid, (pid, ''))[0]
# 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:]
# The SYNC pattern for low-speed/full-speed is KJKJKJKK (0001).
if sync != '00000001':
return 'SYNC INVALID!'
return pid + ' ' + data
class Decoder(srd.Decoder):
api_version = 1
id = 'usb'
name = 'USB'
longname = 'Universal Serial Bus (LS/FS)'
desc = 'USB 1.x (low-speed and full-speed) serial protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['usb']
probes = [
{'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
{'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
]
optional_probes = []
options = {
'signalling': ['Signalling', 'full-speed'],
}
annotations = [
['Text', 'Human-readable text']
]
def __init__(self):
self.sym = 'J'
self.samplenum = 0
self.scount = 0
self.packet = ''
def start(self, metadata):
self.samplerate = metadata['samplerate']
# self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
def report(self):
pass
def decode(self, ss, es, data):
for (self.samplenum, (dp, dm)) in data:
# Note: self.samplenum is the absolute sample number, whereas
# self.scount only counts the number of samples since the
# last change in the D+/D- lines.
self.scount += 1
sym = get_sym(self.options['signalling'], dp, dm)
# Wait for a symbol change (i.e., change in D+/D- lines).
if sym == self.sym:
continue
# if self.scount == 1:
# # We ignore single sample width "pulses", i.e., symbol changes
# # (D+/D- line changes). 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':
if self.options['signalling'] == 'low-speed':
bitrate = 1500000 # 1.5Mb/s (+/- 1.5%)
elif self.options['signalling'] == 'full-speed':
bitrate = 12000000 # 12Mb/s (+/- 0.25%)
bitcount = int((self.scount - 1) * bitrate / self.samplerate)
else:
bitcount = 0
if self.sym == 'SE0':
if bitcount == 1:
# End-Of-Packet (EOP)
self.put(0, 0, self.out_ann,
[0, [packet_decode(self.packet), self.packet]])
else:
# Longer than EOP, assume reset.
self.put(0, 0, self.out_ann, [0, ['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:
self.put(0, 0, self.out_ann, [0, ['BIT STUFF ERROR']])
self.scount = 0
self.sym = sym
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