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1 | ## |
2 | ## This file is part of the sigrok 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, write to the Free Software | |
18 | ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
19 | ## | |
20 | ||
156509ca | 21 | ''' |
c2937021 | 22 | USB (low-speed and full-speed) protocol decoder. |
156509ca | 23 | |
c2937021 | 24 | USB signalling consists of two signal lines, both driven at 3.3V |
156509ca UH |
25 | logic levels. The signals are DP (D+) and DM (D-), and normally operate in |
26 | differential mode. | |
c2937021 UH |
27 | |
28 | Low-speed: The state where DP=1,DM=0 is K, the state DP=0,DM=1 is J. | |
29 | Full-speed: The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K. | |
30 | ||
156509ca | 31 | A state SE0 is defined where DP=DM=0. This common mode signal is used to |
c2937021 | 32 | signal a reset or end of packet. A state SE1 is defined where DP=DM=1. |
156509ca UH |
33 | |
34 | Data transmitted on the USB is encoded with NRZI. A transition from J to K | |
35 | or vice-versa indicates a logic 0, while no transition indicates a logic 1. | |
36 | If 6 ones are transmitted consecutively, a zero is inserted to force a | |
c2937021 UH |
37 | transition. This is known as bit stuffing. |
38 | ||
39 | Data is transferred at a rate of 1.5Mbit/s (low-speed) / 12Mbit/s (full-speed). | |
40 | ||
41 | The SE0 transmitted to signal an end-of-packet is two bit intervals long | |
42 | (low-speed: 1.25uS - 1.50uS, full-speed: 160ns - 175ns). | |
43 | ||
44 | Bit/byte ordering: Bits are sent onto the bus LSB-first. Multibyte fields | |
45 | are transmitted in little-endian order (i.e., LSB to MSB). | |
46 | ||
47 | SYNC field: All packets begin with a SYNC field (8 bits). | |
48 | ||
49 | Packet field format: Packets start with an SOP (Start Of Packet) delimiter | |
50 | that is part of the SYNC field, and end with an EOP (End Of Packet). | |
51 | ||
52 | PID: A PID (packet identifier) follows the SYNC field of every packet. A PID | |
53 | consists of a 4-bit packet type field, and a 4 bit check field. | |
54 | The check field is the one's complement of the packet type field. | |
156509ca | 55 | |
71077f34 UH |
56 | Protocol output format: |
57 | TODO | |
58 | ||
156509ca UH |
59 | Details: |
60 | https://en.wikipedia.org/wiki/USB | |
61 | http://www.usb.org/developers/docs/ | |
62 | ''' | |
63 | ||
64c29e28 UH |
64 | from .usb import * |
65 |