diff options
Diffstat (limited to 'decoders/uart/pd.py')
| -rw-r--r-- | decoders/uart/pd.py | 88 |
1 files changed, 58 insertions, 30 deletions
diff --git a/decoders/uart/pd.py b/decoders/uart/pd.py index b081724..8db3e17 100644 --- a/decoders/uart/pd.py +++ b/decoders/uart/pd.py @@ -75,7 +75,7 @@ class ChannelError(Exception): pass class Decoder(srd.Decoder): - api_version = 2 + api_version = 3 id = 'uart' name = 'UART' longname = 'Universal Asynchronous Receiver/Transmitter' @@ -170,8 +170,6 @@ class Decoder(srd.Decoder): self.stopbit1 = [-1, -1] self.startsample = [-1, -1] self.state = ['WAIT FOR START BIT', 'WAIT FOR START BIT'] - self.oldbit = [1, 1] - self.oldpins = [-1, -1] self.databits = [[], []] def start(self): @@ -186,8 +184,8 @@ class Decoder(srd.Decoder): # The width of one UART bit in number of samples. self.bit_width = float(self.samplerate) / float(self.options['baudrate']) - # Return true if we reached the middle of the desired bit, false otherwise. - def reached_bit(self, rxtx, bitnum): + def get_sample_point(self, rxtx, bitnum): + """Determine absolute sample number of a bit slot's sample point.""" # bitpos is the samplenumber which is in the middle of the # specified UART bit (0 = start bit, 1..x = data, x+1 = parity bit # (if used) or the first stop bit, and so on). @@ -195,14 +193,20 @@ class Decoder(srd.Decoder): # index of the middle sample within bit window is (bit_width - 1) / 2. bitpos = self.frame_start[rxtx] + (self.bit_width - 1) / 2.0 bitpos += bitnum * self.bit_width + return bitpos + + # Return true if we reached the middle of the desired bit, false otherwise. + def reached_bit(self, rxtx, bitnum): + bitpos = self.get_sample_point(rxtx, bitnum) if self.samplenum >= bitpos: return True return False - def wait_for_start_bit(self, rxtx, old_signal, signal): - # The start bit is always 0 (low). As the idle UART (and the stop bit) - # level is 1 (high), the beginning of a start bit is a falling edge. - if not (old_signal == 1 and signal == 0): + def wait_for_start_bit(self, rxtx, signal): + # The caller already has detected an edge. Strictly speaking this + # check on the current signal level is redundant. But it does not + # harm either. + if signal != 0: return # Save the sample number where the start bit begins. @@ -364,29 +368,56 @@ class Decoder(srd.Decoder): self.putp(['STOPBIT', rxtx, self.stopbit1[rxtx]]) self.putg([rxtx + 4, ['Stop bit', 'Stop', 'T']]) - def decode(self, ss, es, data): + def get_wait_cond(self, rxtx, inv): + """ + Determine Decoder.wait() condition for specified UART line. + + Returns condititions that are suitable for Decoder.wait(). Those + conditions either match the falling edge of the START bit, or + the sample point of the next bit time. + """ + + state = self.state[rxtx] + if state == 'WAIT FOR START BIT': + return {rxtx: 'r' if inv else 'f'} + if state == 'GET START BIT': + bitnum = 0 + elif state == 'GET DATA BITS': + bitnum = 1 + self.cur_data_bit[rxtx] + elif state == 'GET PARITY BIT': + bitnum = 1 + self.options['num_data_bits'] + elif state == 'GET STOP BITS': + bitnum = 1 + self.options['num_data_bits'] + bitnum += 0 if self.options['parity_type'] == 'none' else 1 + want_num = self.get_sample_point(rxtx, bitnum) + # want_num = int(want_num + 0.5) + want_num = ceil(want_num) + cond = {'skip': want_num - self.samplenum} + return cond + + def decode(self): if not self.samplerate: raise SamplerateError('Cannot decode without samplerate.') - for (self.samplenum, pins) in data: - # We want to skip identical samples for performance reasons but, - # for now, we can only do that when we are in the idle state - # (meaning both channels are waiting for the start bit). - if self.state == self.idle_state and self.oldpins == pins: - continue - - self.oldpins, (rx, tx) = pins, pins - - if self.options['invert_rx'] == 'yes': + has_pin = [self.has_channel(ch) for ch in (RX, TX)] + if has_pin == [False, False]: + raise ChannelError('Either TX or RX (or both) pins required.') + + opt = self.options + inv = [opt['invert_rx'] == 'yes', opt['invert_tx'] == 'yes'] + + while True: + conds = [] + if has_pin[RX]: + conds.append(self.get_wait_cond(RX, inv[RX])) + if has_pin[TX]: + conds.append(self.get_wait_cond(TX, inv[TX])) + (rx, tx) = self.wait(conds) + if inv[RX]: rx = not rx - if self.options['invert_tx'] == 'yes': + if inv[TX]: tx = not tx - # Either RX or TX (but not both) can be omitted. - has_pin = [rx in (0, 1), tx in (0, 1)] - if has_pin == [False, False]: - raise ChannelError('Either TX or RX (or both) pins required.') - # State machine. for rxtx in (RX, TX): # Don't try to handle RX (or TX) if not supplied. @@ -396,7 +427,7 @@ class Decoder(srd.Decoder): signal = rx if (rxtx == RX) else tx if self.state[rxtx] == 'WAIT FOR START BIT': - self.wait_for_start_bit(rxtx, self.oldbit[rxtx], signal) + self.wait_for_start_bit(rxtx, signal) elif self.state[rxtx] == 'GET START BIT': self.get_start_bit(rxtx, signal) elif self.state[rxtx] == 'GET DATA BITS': @@ -405,6 +436,3 @@ class Decoder(srd.Decoder): self.get_parity_bit(rxtx, signal) elif self.state[rxtx] == 'GET STOP BITS': self.get_stop_bits(rxtx, signal) - - # Save current RX/TX values for the next round. - self.oldbit[rxtx] = signal |