srd: Split USB decoder in two PDs (which stack).

The 'usb_signalling' decoder just decodes symbols from D+/D- levels,
handles bit stuffing and outputs the symbols and (potential) packets.

The 'usb_protocol' decoder takes that output and tried to parse USB
packets from it (SOF, SETUP, IN, OUT, DATA0, and so on).
This is the base decoder on top of which various others will stack
later on.

The two new PDs are work in progress, so we still keep the old 'usb' PD
around for a little while, until the two new ones are fully working and
well-tested.

1 files changed, 137 insertions, 0 deletions

diff --git a/decoders/usb_protocol/usb_protocol.py b/decoders/usb_protocol/usb_protocol.py
new file mode 100644
index 0000000..b1cd33b
--- /dev/null
+++ b/decoders/usb_protocol/usb_protocol.py
@@ -0,0 +1,137 @@
+##
+## This file is part of the sigrok project.
+##
+## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
+## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.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
+##
+
+# USB (low-speed and full-speed) protocol decoder
+
+import sigrokdecode as srd
+
+# 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 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: %s' % sync
+
+    return pid + ' ' + data
+
+class Decoder(srd.Decoder):
+    api_version = 1
+    id = 'usb_protocol'
+    name = 'USB protocol'
+    longname = 'Universal Serial Bus (LS/FS) protocol'
+    desc = 'USB 1.x (low-speed and full-speed) serial protocol.'
+    license = 'gplv2+'
+    inputs = ['usb_signalling']
+    outputs = ['usb_protocol']
+    probes = []
+    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 = ''
+        self.state = 'IDLE'
+
+    def start(self, metadata):
+        self.samplerate = metadata['samplerate']
+        self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb_protocol')
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'usb_protocol')
+
+    def report(self):
+        pass
+
+    def decode(self, ss, es, data):
+        (ptype, pdata) = data
+
+        if ptype == 'PACKET':
+            self.put(0, 0, self.out_ann, [0, [packet_decode(pdata)]])
+
+        # TODO.
+