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'},
)
self.put(self.ss_edge, self.samplenum, self.out_ann, data)
def __init__(self):
+ self.reset()
+
+ def reset(self):
self.ss_edge = None
- self.first_transition = True
- self.bitwidth = None
def start(self):
self.out_ann = self.register(srd.OUTPUT_ANN)
- self.initial_pins = [1] # TODO: Not generally correct.
-
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
if not self.samplerate:
raise SamplerateError('Cannot decode without samplerate.')
+ # Get the first edge on the data line.
+ self.wait({0: 'e'})
+ self.ss_edge = self.samplenum
+
+ # 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:
- # Wait for any transition/edge on the data line.
self.wait({0: 'e'})
- # Get the smallest distance between two transitions
- # and use that to calculate the bitrate/baudrate.
- if self.first_transition:
- self.ss_edge = self.samplenum
- self.first_transition = False
- else:
- b = self.samplenum - self.ss_edge
- if self.bitwidth is 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
+ 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