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1 | ## | |
2 | ## This file is part of the libsigrokdecode project. | |
3 | ## | |
4 | ## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de> | |
5 | ## | |
6 | ## This program is free software; you can redistribute it and/or modify | |
7 | ## it under the terms of the GNU General Public License as published by | |
8 | ## the Free Software Foundation; either version 2 of the License, or | |
9 | ## (at your option) any later version. | |
10 | ## | |
11 | ## This program is distributed in the hope that it will be useful, | |
12 | ## but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | ## GNU General Public License for more details. | |
15 | ## | |
16 | ## You should have received a copy of the GNU General Public License | |
17 | ## along with this program; if not, see <http://www.gnu.org/licenses/>. | |
18 | ## | |
19 | ||
20 | ''' | |
21 | This decoder stacks on top of the 'usb_signalling' PD and decodes the USB | |
22 | (low-speed and full-speed) packet protocol. | |
23 | ||
24 | Protocol layer (USB spec, chapter 8): | |
25 | ||
26 | Bit/byte ordering: Bits are sent onto the bus LSB-first. Multibyte fields | |
27 | are transmitted in little-endian order (i.e., LSB to MSB). | |
28 | ||
29 | SYNC field: All packets begin with a SYNC field (8 bits). | |
30 | ||
31 | Packet field format: Packets start with an SOP (Start Of Packet) delimiter | |
32 | that is part of the SYNC field, and end with an EOP (End Of Packet). | |
33 | ||
34 | PID: A PID (packet identifier) follows the SYNC field of every packet. A PID | |
35 | consists of a 4-bit packet type field, and a 4 bit check field. | |
36 | The check field is the one's complement of the packet type field. | |
37 | ||
38 | Details: | |
39 | https://en.wikipedia.org/wiki/USB | |
40 | http://www.usb.org/developers/docs/ | |
41 | ''' | |
42 | ||
43 | from .pd import Decoder |