]>
Commit | Line | Data |
---|---|---|
2dc6d41c | 1 | ## |
50bd5d25 | 2 | ## This file is part of the libsigrokdecode project. |
2dc6d41c UH |
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 | ||
21 | ''' | |
4c3b1846 | 22 | This PD decodes the USB (low-speed and full-speed) signalling protocol. |
2dc6d41c UH |
23 | |
24 | Electrical/signalling layer (USB spec, chapter 7): | |
25 | ||
26 | USB signalling consists of two signal lines, both driven at 3.3V | |
27 | logic levels. The signals are DP (D+) and DM (D-), and normally operate in | |
28 | differential mode. | |
29 | ||
30 | Low-speed: The state where DP=1,DM=0 is K, the state DP=0,DM=1 is J. | |
31 | Full-speed: The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K. | |
32 | ||
33 | A state SE0 is defined where DP=DM=0. This common mode signal is used to | |
34 | signal a reset or end of packet (EOP). A state SE1 is defined where DP=DM=1. | |
35 | ||
36 | Data transmitted on the USB is encoded with NRZI. A transition from J to K | |
37 | or vice-versa indicates a logic 0, while no transition indicates a logic 1. | |
38 | If 6 ones are transmitted consecutively, a zero is inserted to force a | |
39 | transition. This is known as bit stuffing. | |
40 | ||
41 | Data is transferred at a rate of 1.5Mbit/s (low-speed) / 12Mbit/s (full-speed). | |
42 | ||
43 | The SE0 transmitted to signal an end-of-packet is two bit intervals long | |
44 | (low-speed: 1.25uS - 1.50uS, full-speed: 160ns - 175ns). | |
45 | ||
2dc6d41c UH |
46 | Details: |
47 | https://en.wikipedia.org/wiki/USB | |
48 | http://www.usb.org/developers/docs/ | |
49 | ''' | |
50 | ||
24c74fd3 | 51 | from .pd import * |
2dc6d41c | 52 |