--- /dev/null
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2014 Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
+##
+## 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
+##
+
+import sigrokdecode as srd
+
+# Helper dictionary for edge detection.
+edge_detector = {
+ 'rising': lambda x, y: bool(not x and y),
+ 'falling': lambda x, y: bool(x and not y),
+ 'both': lambda x, y: bool(x ^ y),
+}
+
+class SamplerateError(Exception):
+ pass
+
+class Decoder(srd.Decoder):
+ api_version = 2
+ id = 'jitter'
+ name = 'Jitter'
+ longname = 'Timing jitter calculation'
+ desc = 'Retrieves the timing jitter between two digital signals.'
+ license = 'gplv2+'
+ inputs = ['logic']
+ outputs = ['jitter']
+ channels = (
+ {'id': 'clk', 'name': 'Clock', 'desc': 'Clock reference channel'},
+ {'id': 'sig', 'name': 'Resulting signal', 'desc': 'Resulting signal controlled by the clock'},
+ )
+ options = (
+ {'id': 'clk_polarity', 'desc': 'Clock edge polarity',
+ 'default': 'rising', 'values': ('rising', 'falling', 'both')},
+ {'id': 'sig_polarity', 'desc': 'Resulting signal edge polarity',
+ 'default': 'rising', 'values': ('rising', 'falling', 'both')},
+ )
+ annotations = (
+ ('jitter', 'Jitter value'),
+ ('clk_missed', 'Clock missed'),
+ ('sig_missed', 'Signal missed'),
+ )
+ annotation_rows = (
+ ('jitter', 'Jitter values', (0,)),
+ ('clk_missed', 'Clock missed', (1,)),
+ ('sig_missed', 'Signal missed', (2,)),
+ )
+
+ def __init__(self, **kwargs):
+ self.state = 'CLK'
+ self.samplerate = None
+ self.oldpin = None
+ self.oldclk = self.oldsig = None
+ self.clk_start = None
+ self.sig_start = None
+ self.clk_missed = 0
+ self.sig_missed = 0
+
+ def start(self):
+ self.clk_edge = edge_detector[self.options['clk_polarity']]
+ self.sig_edge = edge_detector[self.options['sig_polarity']]
+ self.out_ann = self.register(srd.OUTPUT_ANN)
+ self.out_clk_missed = self.register(srd.OUTPUT_META,
+ meta=(int, 'Clock missed', 'Clock transition missed'))
+ self.out_sig_missed = self.register(srd.OUTPUT_META,
+ meta=(int, 'Signal missed', 'Resulting signal transition missed'))
+
+ def metadata(self, key, value):
+ if key == srd.SRD_CONF_SAMPLERATE:
+ self.samplerate = value
+
+ # Helper function for jitter time annotations.
+ def putx(self, delta):
+ # Adjust granularity.
+ if delta == 0 or delta >= 1:
+ delta_s = u"%us" % (delta)
+ elif delta <= 1e-12:
+ delta_s = u"%.1ffs" % (delta * 1e15)
+ elif delta <= 1e-9:
+ delta_s = u"%.1fps" % (delta * 1e12)
+ elif delta <= 1e-6:
+ delta_s = u"%.1fns" % (delta * 1e9)
+ elif delta <= 1e-3:
+ delta_s = u"%.1fμs" % (delta * 1e6)
+ else:
+ delta_s = u"%.1fms" % (delta * 1e3)
+
+ self.put(self.clk_start, self.sig_start, self.out_ann, [0, [delta_s]])
+
+ # Helper function for missed clock and signal annotations.
+ def putm(self, data):
+ self.put(self.samplenum, self.samplenum, self.out_ann, data)
+
+ def decode(self, ss, es, data):
+ if not self.samplerate:
+ raise SamplerateError('Cannot decode without samplerate.')
+
+ for (self.samplenum, pins) in data:
+ # We are only interested in transitions.
+ if self.oldpin == pins:
+ continue
+
+ self.oldpin, (clk, sig) = pins, pins
+
+ if self.oldclk is None and self.oldsig is None:
+ self.oldclk, self.oldsig = clk, sig
+
+ # State machine:
+ # For each sample we can move 2 steps forward in the state machine.
+ while True:
+
+ # Clock state has the lead.
+ if self.state == 'CLK':
+ if self.clk_start == self.samplenum:
+ # Clock transition already treated.
+ # We have done everything we can with this sample.
+ break
+ else:
+ if self.clk_edge(self.oldclk, clk) is True:
+ # Clock edge found.
+ # We note the sample and move to the next state.
+ self.clk_start = self.samplenum
+ self.state = 'SIG'
+ else:
+ if self.sig_start is not None \
+ and self.sig_start != self.samplenum \
+ and self.sig_edge(self.oldsig, sig) is True:
+ # If any transition in the resulting signal
+ # occurs while we are waiting for a clock,
+ # we increase the missed signal counter.
+ self.sig_missed += 1
+ self.put(ss, self.samplenum, self.out_sig_missed, self.sig_missed)
+ self.putm([2, ['Missed signal', 'MS']])
+ # No clock edge found, we have done everything we
+ # can with this sample.
+ break
+ if self.state == 'SIG':
+ if self.sig_start == self.samplenum:
+ # Signal transition already treated.
+ # We have done everything we can with this sample.
+ break
+ else:
+ if self.sig_edge(self.oldsig, sig) is True:
+ # Signal edge found.
+ # We note the sample, calculate the jitter
+ # and move to the next state.
+ self.sig_start = self.samplenum
+ self.state = 'CLK'
+ # Calculate and report the timing jitter.
+ self.putx((self.sig_start - self.clk_start) / self.samplerate)
+ else:
+ if self.clk_start != self.samplenum \
+ and self.clk_edge(self.oldclk, clk) is True:
+ # If any transition in the clock signal
+ # occurs while we are waiting for a resulting
+ # signal, we increase the missed clock counter.
+ self.clk_missed += 1
+ self.put(ss, self.samplenum, self.out_clk_missed, self.clk_missed)
+ self.putm([1, ['Missed clock', 'MC']])
+ # No resulting signal edge found, we have done
+ # everything we can with this sample.
+ break
+
+ # Save current CLK/SIG values for the next round.
+ self.oldclk, self.oldsig = clk, sig
projects / libsigrokdecode.git / commitdiff