##
## This file is part of the libsigrokdecode project.
##
-## Copyright (C) 2013 Uwe Hermann <uwe@hermann-uwe.de>
+## Copyright (C) 2013-2016 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
## 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
+## along with this program; if not, see <http://www.gnu.org/licenses/>.
##
import sigrokdecode as srd
+class SamplerateError(Exception):
+ pass
+
class Decoder(srd.Decoder):
- api_version = 1
+ api_version = 3
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']
+ outputs = []
+ tags = ['Clock/timing', 'Util']
channels = (
{'id': 'data', 'name': 'Data', 'desc': 'Data line'},
)
def putx(self, data):
self.put(self.ss_edge, self.samplenum, self.out_ann, data)
- def __init__(self, **kwargs):
- self.olddata = None
+ def __init__(self):
+ self.reset()
+
+ def reset(self):
self.ss_edge = None
- self.first_transition = True
- self.bitwidth = None
def start(self):
- # self.out_python = self.register(srd.OUTPUT_PYTHON)
self.out_ann = self.register(srd.OUTPUT_ANN)
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
- self.samplerate = value;
-
- def decode(self, ss, es, data):
- if self.samplerate is None:
- raise Exception("Cannot decode without samplerate.")
- for (self.samplenum, pins) in data:
-
- data = pins[0]
-
- # Wait for any transition on the data line.
- if data == self.olddata:
- continue
+ self.samplerate = value
- # Initialize first self.olddata with the first sample value.
- if self.olddata == None:
- self.olddata = data
- continue
+ def decode(self):
+ if not self.samplerate:
+ raise SamplerateError('Cannot decode without samplerate.')
- # 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
+ # Get the first edge on the data line.
+ self.wait({0: 'e'})
+ self.ss_edge = self.samplenum
- self.olddata = data
+ # Get any subsequent edge on the data line. Get the smallest
+ # distance between any two transitions, assuming it corresponds
+ # to one bit time of the respective bitrate of the input stream.
+ # This heuristics keeps getting better for longer captures.
+ bitwidth = None
+ while True:
+ self.wait({0: 'e'})
+ b = self.samplenum - self.ss_edge
+ if bitwidth is None or b < bitwidth:
+ bitwidth = b
+ bitrate = int(float(self.samplerate) / float(b))
+ self.putx([0, ['%d' % bitrate]])
+ self.ss_edge = self.samplenum