USB PD BMC decoder
Decode and packetize Biphase mark coding (aka differential Manchester)
as used in the USB Power Delivery v2.
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=none
TEST=none
Change-Id: Ic4718f64a054c00aa0f3fc3578c4f7e83d72ef8b
diff --git a/decoders/usb_pd_bmc/__init__.py b/decoders/usb_pd_bmc/__init__.py
new file mode 100644
index 0000000..85a8dbe
--- /dev/null
+++ b/decoders/usb_pd_bmc/__init__.py
@@ -0,0 +1,21 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Google, Inc
+##
+## 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.
+##
+
+"""
+USB Power Delivery - baseband protocol decoder / checker
+"""
+
+from .pd import *
diff --git a/decoders/usb_pd_bmc/pd.py b/decoders/usb_pd_bmc/pd.py
new file mode 100644
index 0000000..67356f9
--- /dev/null
+++ b/decoders/usb_pd_bmc/pd.py
@@ -0,0 +1,152 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Google, Inc
+##
+## 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.
+##
+
+import sigrokdecode as srd
+
+# 600Khz datarate
+UI_US = 1000000/600000.0
+
+# Threshold to discriminate half-1 from 0
+THRESHOLD_US = (UI_US + 2 * UI_US) / 2
+
+
+class Decoder(srd.Decoder):
+ api_version = 2
+ id = 'usb_pd_bmc'
+ name = 'pd_bmc'
+ longname = 'Biphase Mark Decoder for USB Power Delivery baseband protocol'
+ desc = 'Power Delivery protocol over CC wire on USB type-C'
+ license = 'gplv2+'
+ inputs = ['logic']
+ outputs = ['pd_packet']
+ channels = (
+ {'id': 'cc', 'name': 'CC', 'desc': 'Control channel'},
+ )
+ options = (
+ )
+ annotations = (
+ ('packet', 'USB-PD packet'),
+ ('bits', 'decoded BMC'),
+ ('warnings', 'Human-readable warning'),
+ )
+ annotation_rows = (
+ ('bits', 'Bits', (1,)),
+ ('title', 'packet', (0,)),
+ ('warnings', 'Warnings', (2,)),
+ )
+
+ def us2samples(self, us):
+ if self.samplerate is None:
+ raise Exception("Need the samplerate.")
+ return int(us * self.samplerate / 1000000)
+
+ def __init__(self, **kwargs):
+ self.samplerate = None
+ self.samplenum = 0
+ self.seq = 0
+ self.previous = 0
+ self.oldpins = [0]
+ self.startsample = None
+ self.packet = []
+ self.edges = []
+ self.half_one = False
+ self.start_one = 0
+
+ def metadata(self, key, value):
+ if key == srd.SRD_CONF_SAMPLERATE:
+ self.samplerate = value
+ # 0 is 2 UI, space larger than 1.5x 0 is definitely wrong
+ self.maxbit = self.us2samples(3 * UI_US)
+ # duration threshold between half 1 and 0
+ self.threshold = self.us2samples(THRESHOLD_US)
+
+ def start(self):
+ self.out_python = self.register(srd.OUTPUT_PYTHON)
+ self.out_ann = self.register(srd.OUTPUT_ANN)
+ self.out_binary = self.register(srd.OUTPUT_BINARY)
+ self.out_bitrate = self.register(srd.OUTPUT_META,
+ meta=(int, 'Bitrate', 'Bitrate during the packet'))
+
+ def putbitx(self, start, data):
+ self.put(start, self.samplenum, self.out_ann, data)
+
+ def putx(self, data):
+ self.put(self.startsample, self.previous, self.out_ann, data)
+
+ def putp(self, data):
+ self.put(self.startsample, self.previous, self.out_python, data)
+
+ def putb(self, data):
+ self.put(self.startsample, self.previous, self.out_binary, data)
+
+ def decode(self, ss, es, data):
+ if self.samplerate is None:
+ raise Exception("Cannot decode without samplerate.")
+ for (self.samplenum, pins) in data:
+ # find edges ...
+ if self.oldpins == pins:
+ continue
+
+ self.oldpins, (cc,) = pins, pins
+
+ # First sample of the packet, just record the start date
+ if not self.startsample:
+ self.startsample = self.samplenum
+ self.previous = self.samplenum
+ continue
+
+ diff = self.samplenum - self.previous
+
+ # Large idle : use it as the end of packet
+ if diff > self.maxbit:
+ tstamp = float(self.startsample) / self.samplerate
+ #brate float(self.previous - self.start) / len(self.packet) / self.samplerate if len(self.packet) else 0
+ # the last edge of the packet
+ self.edges.append(self.previous)
+ # Export the packet
+ self.putx([0, ['BMC %d' % (self.seq),'PD']])
+ self.putp({'BITS': self.packet, 'EDGES':self.edges})
+ #self.putb((1, bytes(self.packet))
+ # Reset for next packet
+ self.startsample = self.samplenum
+ self.packet = []
+ self.edges = []
+ self.half_one = False
+ self.start_one = 0
+ self.seq += 1
+ else: # add the bit to the packet
+ is_zero = diff > self.threshold
+ if is_zero and not self.half_one:
+ self.packet.append(0)
+ self.putbitx(self.previous,[1,['0','0']])
+ self.edges.append(self.previous)
+ elif not is_zero and self.half_one:
+ self.packet.append(1)
+ self.putbitx(self.start_one,[1,['1','1']])
+ self.edges.append(self.start_one)
+ self.half_one = False
+ elif not is_zero and not self.half_one:
+ self.half_one = True
+ self.start_one = self.previous
+ else: # Invalid BMC sequence
+ self.putbitx(self.start_one,[2,['invalid duration %2.2fus' % (float(diff)*1000000/self.samplerate),'%d' % (diff)]])
+ self.putbitx(self.start_one,[1,['X','X']])
+ #TODO try to recover
+ self.packet.append(0)
+ self.edges.append(self.previous)
+ self.half_one = False
+ self.previous = self.samplenum
+