srd: Add initial DCF77 protocol decoder.

Works quite well already, but not all details of the protocol are
implemented, yet.

1 files changed, 279 insertions, 0 deletions

diff --git a/decoders/dcf77.py b/decoders/dcf77.py
new file mode 100644
index 0000000..7002660
--- /dev/null
+++ b/decoders/dcf77.py
@@ -0,0 +1,279 @@
+##
+## This file is part of the sigrok project.
+##
+## Copyright (C) 2012 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
+##
+
+#
+# DCF77 protocol decoder
+#
+# More information:
+# http://en.wikipedia.org/wiki/DCF77
+#
+
+#
+# Protocol output format:
+# TODO
+#
+
+import sigrokdecode as srd
+import calendar
+
+# States
+WAIT_FOR_RISING_EDGE = 0
+GET_BIT = 1
+
+# Annotation feed formats
+ANN_ASCII = 0
+
+# Return the specified BCD number (max. 8 bits) as integer.
+def bcd2int(b):
+    return (b & 0x0f) + ((b >> 4) * 10)
+
+class Decoder(srd.Decoder):
+    id = 'dcf77'
+    name = 'DCF77'
+    longname = 'TODO.'
+    desc = 'TODO.'
+    longdesc = 'TODO.'
+    author = 'Uwe Hermann'
+    email = 'uwe@hermann-uwe.de'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['dcf77']
+    probes = [
+        {'id': 'data', 'name': 'DATA', 'desc': 'DATA line'},
+    ]
+    options = {}
+    annotations = [
+        # ANN_ASCII
+        ['ASCII', 'TODO: description'],
+    ]
+
+    def __init__(self, **kwargs):
+        self.state = WAIT_FOR_RISING_EDGE
+        self.oldval = None
+        self.samplenum = 0
+        self.bit_start = 0
+        self.bit_start_old = 0
+        self.bitcount = 0 # Counter for the DCF77 bits (0..58)
+        self.dcf77_bitnumber_is_known = 0
+
+    def start(self, metadata):
+        self.samplerate = metadata['samplerate']
+        # self.out_proto = self.add(srd.OUTPUT_PROTO, 'dcf77')
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'dcf77')
+
+    def report(self):
+        pass
+
+    # TODO: Which range to use? Only the 100ms/200ms or full second?
+    def handle_dcf77_bit(self, bit):
+        c = self.bitcount
+        a = self.out_ann
+        ss = es = 0 # FIXME
+
+        # Create one annotation for each DCF77 bit (containing the 0/1 value).
+        # Use 'Unknown DCF77 bit x: val' if we're not sure yet which of the
+        # 0..58 bits it is (because we haven't seen a 'new minute' marker yet).
+        # Otherwise, use 'DCF77 bit x: val'.
+        s = '' if self.dcf77_bitnumber_is_known else 'Unknown '
+        self.put(ss, es, a, [0, ['%sDCF77 bit %d: %d' % (s, c, bit)]])
+
+        # If we're not sure yet which of the 0..58 DCF77 bits we have, return.
+        # We don't want to decode bogus data.
+        if not self.dcf77_bitnumber_is_known:
+            return
+
+        # Output specific "decoded" annotations for the respective DCF77 bits.
+        if c == 0:
+            # Start of minute: DCF bit 0.
+            if bit == 0:
+                self.put(ss, es, a, [0, ['Start of minute (always 0)']])
+            else:
+                self.put(ss, es, a, [0, ['ERROR: Start of minute != 0']])
+        elif c in range(1, 14 + 1):
+            # Special bits (civil warnings, weather forecast): DCF77 bits 1-14.
+            if c == 1:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 1))
+            if c == 14:
+                self.put(ss, es, a, [0, ['Special bits: %s' % bin(self.tmp)]])
+        elif c == 15:
+            s = '' if (bit == 1) else 'not '
+            self.put(ss, es, a, [0, ['Call bit is %sset' % s]])
+            # TODO: Previously this bit indicated use of the backup antenna.
+        elif c == 16:
+            s = '' if (bit == 1) else 'not '
+            self.put(ss, es, a, [0, ['Summer time announcement %sactive' % s]])
+        elif c == 17:
+            s = '' if (bit == 1) else 'not '
+            self.put(ss, es, a, [0, ['CEST is %sin effect' % s]])
+        elif c == 18:
+            s = '' if (bit == 1) else 'not '
+            self.put(ss, es, a, [0, ['CET is %sin effect' % s]])
+        elif c == 19:
+            s = '' if (bit == 1) else 'not '
+            self.put(ss, es, a, [0, ['Leap second announcement %sactive' % s]])
+        elif c == 20:
+            # Start of encoded time: DCF bit 20.
+            if bit == 1:
+                self.put(ss, es, a, [0, ['Start of encoded time (always 1)']])
+            else:
+                self.put(ss, es, a,
+                         [0, ['ERROR: Start of encoded time != 1']])
+        elif c in range(21, 27 + 1):
+            # Minutes (0-59): DCF77 bits 21-27 (BCD format).
+            if c == 21:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 21))
+            if c == 27:
+                self.put(ss, es, a, [0, ['Minutes: %d' % bcd2int(self.tmp)]])
+        elif c == 28:
+            # Even parity over minute bits (21-28): DCF77 bit 28.
+            self.tmp |= (bit << (c - 21))
+            parity = bin(self.tmp).count('1')
+            s = 'OK' if ((parity % 2) == 0) else 'INVALID!'
+            self.put(ss, es, a, [0, ['Minute parity: %s' % s]])
+        elif c in range(29, 34 + 1):
+            # Hours (0-23): DCF77 bits 29-34 (BCD format).
+            if c == 29:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 29))
+            if c == 34:
+                self.put(ss, es, a, [0, ['Hours: %d' % bcd2int(self.tmp)]])
+        elif c == 35:
+            # Even parity over hour bits (29-35): DCF77 bit 35.
+            self.tmp |= (bit << (c - 29))
+            parity = bin(self.tmp).count('1')
+            s = 'OK' if ((parity % 2) == 0) else 'INVALID!'
+            self.put(ss, es, a, [0, ['Hour parity: %s' % s]])
+        elif c in range(36, 41 + 1):
+            # Day of month (1-31): DCF77 bits 36-41 (BCD format).
+            if c == 36:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 36))
+            if c == 41:
+                self.put(ss, es, a, [0, ['Day: %d' % bcd2int(self.tmp)]])
+        elif c in range(42, 44 + 1):
+            # Day of week (1-7): DCF77 bits 42-44 (BCD format).
+            # A value of 1 means Monday, 7 means Sunday.
+            if c == 42:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 42))
+            if c == 44:
+                d = bcd2int(self.tmp)
+                dn = calendar.day_name[d - 1] # day_name[0] == Monday
+                self.put(ss, es, a, [0, ['Day of week: %d (%s)' % (d, dn)]])
+        elif c in range(45, 49 + 1):
+            # Month (1-12): DCF77 bits 45-49 (BCD format).
+            if c == 45:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 45))
+            if c == 49:
+                m = bcd2int(self.tmp)
+                mn = calendar.month_name[m] # month_name[1] == January
+                self.put(ss, es, a, [0, ['Month: %d (%s)' % (m, mn)]])
+        elif c in range(50, 57 + 1):
+            # Year (0-99): DCF77 bits 50-57 (BCD format).
+            if c == 50:
+                self.tmp = bit
+            else:
+                self.tmp |= (bit << (c - 50))
+            if c == 57:
+                self.put(ss, es, a, [0, ['Year: %d' % bcd2int(self.tmp)]])
+        elif c == 58:
+            # Even parity over date bits (36-58): DCF77 bit 58.
+            self.tmp |= (bit << (c - 50))
+            parity = bin(self.tmp).count('1')
+            s = 'OK' if ((parity % 2) == 0) else 'INVALID!'
+            self.put(ss, es, a, [0, ['Date parity: %s' % s]])
+        else:
+            raise Exception('Invalid DCF77 bit: %d' % c)
+
+    def decode(self, ss, es, data):
+        for samplenum, (pon, val) in data: # FIXME
+
+            self.samplenum += 1 # FIXME. Use samplenum. Off-by-one?
+
+            if self.state == WAIT_FOR_RISING_EDGE:
+                # Wait until the next rising edge occurs.
+                if not (self.oldval == 0 and val == 1):
+                    self.oldval = val
+                    continue
+
+                # Save the sample number where the DCF77 bit begins.
+                self.bit_start = self.samplenum
+
+                # Calculate the length (in ms) between two rising edges.
+                len_edges = self.bit_start - self.bit_start_old
+                len_edges_ms = int((len_edges / self.samplerate) * 1000)
+
+                # The time between two rising edges is usually around 1000ms.
+                # For DCF77 bit 59, there is no rising edge at all, i.e. the
+                # time between DCF77 bit 59 and DCF77 bit 0 (of the next
+                # minute) is around 2000ms. Thus, if we see an edge with a
+                # 2000ms distance to the last one, this edge marks the
+                # beginning of a new minute (and DCF77 bit 0 of that minute).
+                if len_edges_ms in range(1600, 2400 + 1):
+                    self.put(ss, es, self.out_ann, [0, ['New minute starts']])
+                    self.bitcount = 0
+                    self.bit_start_old = self.bit_start
+                    self.dcf77_bitnumber_is_known = 1
+                    # Don't switch to GET_BIT state this time.
+                    continue
+
+                self.bit_start_old = self.bit_start
+                self.state = GET_BIT
+
+            elif self.state == GET_BIT:
+                # Wait until the next falling edge occurs.
+                if not (self.oldval == 1 and val == 0):
+                    self.oldval = val
+                    continue
+
+                # Calculate the length (in ms) of the current high period.
+                len_high = self.samplenum - self.bit_start
+                len_high_ms = int((len_high / self.samplerate) * 1000)
+
+                # If the high signal was 100ms long, that encodes a 0 bit.
+                # If it was 200ms long, that encodes a 1 bit.
+                if len_high_ms in range(40, 160 + 1):
+                    bit = 0
+                elif len_high_ms in range(161, 260 + 1):
+                    bit = 1
+                else:
+                    bit = -1 # TODO: Error?
+
+                # TODO: There's no bit 59, make sure none is decoded.
+                if bit in (0, 1) and self.bitcount in range(0, 58 + 1):
+                    self.handle_dcf77_bit(bit)
+                    self.bitcount += 1
+
+                self.state = WAIT_FOR_RISING_EDGE
+
+            else:
+                raise Exception('Invalid state: %s' % self.state)
+
+            self.oldval = val
+