usb_request: USB transaction decoder and PCAP generator

The new decoder stacks on top of the usb_packet PD. It adds one new
annotation row, and is able to save the decoded data as PCAP trace.

It has been successfully tested against all traces in sigrok-dumps and
some more traces.

1 files changed, 50 insertions, 0 deletions

diff --git a/decoders/usb_request/__init__.py b/decoders/usb_request/__init__.py
new file mode 100644
index 0000000..7a156ff
--- /dev/null
+++ b/decoders/usb_request/__init__.py
@@ -0,0 +1,50 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2015 Stefan Brüns <stefan.bruens@rwth-aachen.de>
+##
+## 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
+##
+
+'''
+This decoder stacks on top of the 'usb_packet' PD and decodes the USB
+(low-speed and full-speed) transactions.
+
+Transactions and requests are tracked per device address and endpoint.
+
+Tracking of CONTROL requests is quite accurate, as these always start with
+a SETUP token and are completed by an IN or OUT transaction, the status
+packet. All transactions during the DATA stage are combined.
+
+For BULK and INTERRUPT requests, each transaction starts with an IN or OUT
+request, and is considered completed after the first transaction containing
+data has been ACKed. Normally a request is only completed after a short or
+zero length packet, but this would require knowledge about the max packet
+size of an endpoint.
+
+All INTERRUPT requests are treated as BULK requests, as on the link layer
+both are identical.
+
+The PCAP binary output contains 'SUBMIT' and 'COMPLETE' records. For
+CONTROL request, the SUBMIT contains the SETUP request, the data is
+either contained in the SUBMIT (Host-to-Device) or the COMPLETE
+(Device-to-Host) record.
+
+Details:
+https://en.wikipedia.org/wiki/USB
+http://www.usb.org/developers/docs/
+'''
+
+from .pd import Decoder