Add a 'guess_bitrate' protocol decoder.

This PD tries to guess / detect / estimate a bitrate of e.g. some
UART communication snippet or other protocols.

3 files changed, 152 insertions, 0 deletions

diff --git a/decoders/guess_bitrate/Makefile.am b/decoders/guess_bitrate/Makefile.am
new file mode 100644
index 0000000..7c162f6
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+++ b/decoders/guess_bitrate/Makefile.am
@@ -0,0 +1,26 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2013 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
+##
+
+pkgdatadir = $(DECODERS_DIR)/guess_bitrate
+
+dist_pkgdata_DATA = __init__.py pd.py
+
+CLEANFILES = *.pyc
+
diff --git a/decoders/guess_bitrate/__init__.py b/decoders/guess_bitrate/__init__.py
new file mode 100644
index 0000000..86f9466
--- /dev/null
+++ b/decoders/guess_bitrate/__init__.py
@@ -0,0 +1,38 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2013 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
+##
+
+'''
+This protocol decoder tries to guess the bitrate / baudrate of the
+communication on the specified probe. Typically this will be used to
+guess / detect the baudrate used in a UART communication snippet, but it
+could also be used to guess bitrates of certain other protocols or buses.
+
+It should be noted that this is nothing more than a simple guess / heuristic,
+and that there are various cases in practice where the detection of the
+bitrate or baudrate will not necessarily have the expected result.
+
+The precision of the estimated bitrate / baudrate will also depend on the
+samplerate used to sample the respective probe. For good results it is
+recommended to use a logic analyzer samplerate that is much higher than
+the expected bitrate/baudrate that might be used on the probe.
+'''
+
+from .pd import *
+
diff --git a/decoders/guess_bitrate/pd.py b/decoders/guess_bitrate/pd.py
new file mode 100644
index 0000000..585bd76
--- /dev/null
+++ b/decoders/guess_bitrate/pd.py
@@ -0,0 +1,88 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2013 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
+##
+
+# Bitrate / baudrate guessing protocol decoder
+
+import sigrokdecode as srd
+
+class Decoder(srd.Decoder):
+    api_version = 1
+    id = 'guess_bitrate'
+    name = 'Guess bitrate'
+    longname = 'Guess bitrate/baudrate'
+    desc = 'Guess the bitrate/baudrate of a UART (or other) protocol.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['guess_bitrate']
+    probes = [
+        {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
+    ]
+    optional_probes = []
+    options = {}
+    annotations = [
+        ['bitrate', 'Bitrate / baudrate'],
+    ]
+
+    def putx(self, data):
+        self.put(self.ss_edge, self.samplenum, self.out_ann, data)
+
+    def __init__(self, **kwargs):
+        self.olddata = None
+        self.ss_edge = None
+        self.first_transition = True
+        self.bitwidth = None
+
+    def start(self, metadata):
+        self.samplerate = metadata['samplerate']
+        # self.out_proto = self.add(srd.OUTPUT_PROTO, 'guess_bitrate')
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'guess_bitrate')
+
+    def report(self):
+        pass
+
+    def decode(self, ss, es, data):
+        for (self.samplenum, pins) in data:
+
+            data = pins[0]
+
+            # Wait for any transition on the data line.
+            if data == self.olddata:
+                continue
+
+            # Initialize first self.olddata with the first sample value.
+            if self.olddata == None:
+                self.olddata = data
+                continue
+
+            # Get the smallest distance between two transitions
+            # and use that to calculate the bitrate/baudrate.
+            if self.first_transition == True:
+                self.ss_edge = self.samplenum
+                self.first_transition = False
+            else:
+                b = self.samplenum - self.ss_edge
+                if self.bitwidth == None or b < self.bitwidth:
+                    self.bitwidth = b
+                    bitrate = int(float(self.samplerate) / float(b))
+                    self.putx([0, ['%d' % bitrate]])
+                self.ss_edge = self.samplenum
+
+            self.olddata = data
+