Add an rgb_led_ws281x decoder.

This decoder handles the WS2812B protocol (and possibly WS2811).

Example dump already exists: led/ws281x/ws281x_4ch_5mhz.sr.

Signed-off-by: Vladimir Ermakov <vooon341@gmail.com>

2 files changed, 156 insertions, 0 deletions

diff --git a/decoders/rgb_led_ws281x/__init__.py b/decoders/rgb_led_ws281x/__init__.py
new file mode 100644
index 0000000..63135a4
--- /dev/null
+++ b/decoders/rgb_led_ws281x/__init__.py
@@ -0,0 +1,28 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2016 Vladimir Ermakov <vooon341@gmail.com>
+##
+## 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 3 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
+##
+
+'''
+WS281x RGB LED protocol decoder.
+
+Details:
+https://cpldcpu.wordpress.com/2014/01/14/light_ws2812-library-v2-0-part-i-understanding-the-ws2812/
+'''
+
+from .pd import Decoder
diff --git a/decoders/rgb_led_ws281x/pd.py b/decoders/rgb_led_ws281x/pd.py
new file mode 100644
index 0000000..e317b71
--- /dev/null
+++ b/decoders/rgb_led_ws281x/pd.py
@@ -0,0 +1,128 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2016 Vladimir Ermakov <vooon341@gmail.com>
+##
+## 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 3 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
+##
+
+import sigrokdecode as srd
+from functools import reduce
+
+class SamplerateError(Exception):
+    pass
+
+class Decoder(srd.Decoder):
+    api_version = 2
+    id = 'rgb_led_ws281x'
+    name = 'RGB LED (WS281x)'
+    longname = 'RGB LED string decoder (WS281x)'
+    desc = 'RGB LED string protocol (WS281x).'
+    license = 'gplv3+'
+    inputs = ['logic']
+    outputs = ['rgb_led_ws281x']
+    channels = (
+        {'id': 'din', 'name': 'DIN', 'desc': 'DIN data line'},
+    )
+    annotations = (
+        ('bit', 'Bit'),
+        ('reset', 'RESET'),
+        ('rgb', 'RGB'),
+    )
+    annotation_rows = (
+        ('bit', 'Bits', (0, 1)),
+        ('rgb', 'RGB', (2,)),
+    )
+
+    def __init__(self, **kwargs):
+        self.samplerate = None
+        self.oldpin = None
+        self.packet_ss = None
+        self.ss = None
+        self.es = None
+        self.bits = []
+        self.inreset = False
+
+    def start(self):
+        self.out_ann = self.register(srd.OUTPUT_ANN)
+
+    def metadata(self, key, value):
+        if key == srd.SRD_CONF_SAMPLERATE:
+            self.samplerate = value
+
+    def handle_bits(self, samplenum):
+        if len(self.bits) == 24:
+            grb = reduce(lambda a, b: (a << 1) | b, self.bits)
+            rgb = (grb & 0xff0000) >> 8 | (grb & 0x00ff00) << 8 | (grb & 0x0000ff)
+            self.put(self.packet_ss, samplenum, self.out_ann,
+                     [2, ['#%06x' % rgb]])
+            self.bits = []
+            self.packet_ss = None
+
+    def decode(self, ss, es, data):
+        if not self.samplerate:
+            raise SamplerateError('Cannot decode without samplerate.')
+
+        for (samplenum, (pin, )) in data:
+            if self.oldpin is None:
+                self.oldpin = pin
+                continue
+
+            # Check RESET condition (manufacturer recommends 50 usec minimal,
+            # but real minimum is ~10 usec).
+            if not self.inreset and not pin and self.es is not None and \
+                    (samplenum - self.es) / self.samplerate > 50e-6:
+
+                # Decode last bit value.
+                tH = (self.es - self.ss) / self.samplerate
+                bit_ = True if tH >= 625e-9 else False
+
+                self.bits.append(bit_)
+                self.handle_bits(self.es)
+
+                self.put(self.ss, self.es, self.out_ann, [0, ['%d' % bit_]])
+                self.put(self.es, samplenum, self.out_ann,
+                         [1, ['RESET', 'RST', 'R']])
+
+                self.inreset = True
+                self.bits = []
+                self.packet_ss = None
+                self.ss = None
+
+            if not self.oldpin and pin:
+                # Rising edge.
+                if self.ss and self.es:
+                    period = samplenum - self.ss
+                    duty = self.es - self.ss
+                    # Ideal duty for T0H: 33%, T1H: 66%.
+                    bit_ = (duty / period) > 0.5
+
+                    self.put(self.ss, samplenum, self.out_ann,
+                             [0, ['%d' % bit_]])
+
+                    self.bits.append(bit_)
+                    self.handle_bits(samplenum)
+
+                if self.packet_ss is None:
+                    self.packet_ss = samplenum
+
+                self.ss = samplenum
+
+            elif self.oldpin and not pin:
+                # Falling edge.
+                self.inreset = False
+                self.es = samplenum
+
+            self.oldpin = pin