Add initial version of PS/2 decoder

2 files changed, 144 insertions, 0 deletions

diff --git a/decoders/ps2/__init__.py b/decoders/ps2/__init__.py
new file mode 100644
index 0000000..75c4768
--- /dev/null
+++ b/decoders/ps2/__init__.py
@@ -0,0 +1,26 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2016 Daniel Schulte <trilader@schroedingers-bit.net>
+##
+## 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, see <http://www.gnu.org/licenses/>.
+##
+
+'''
+This protocol decoder can decode PS/2 device -> host communication.
+
+Host -> device communication is currently not supported.
+'''
+
+from .pd import Decoder
diff --git a/decoders/ps2/pd.py b/decoders/ps2/pd.py
new file mode 100644
index 0000000..5b15c6e
--- /dev/null
+++ b/decoders/ps2/pd.py
@@ -0,0 +1,118 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2016 Daniel Schulte <trilader@schroedingers-bit.net>
+##
+## 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
+##
+
+import sigrokdecode as srd
+
+class Ann:
+    START, STOP, PARITY, WORD = range(4)
+
+class Decoder(srd.Decoder):
+    api_version = 2
+    id = 'ps2'
+    name = 'PS/2'
+    longname = 'PS/2'
+    desc = 'PS/2 keyboard/mouse interface.'
+    license = 'gplv2+'
+    inputs = ['logic']
+    outputs = ['ps2']
+    optional_channels = (
+        {'id': 'clk', 'name': 'Clock', 'desc': 'Clock line'},
+        {'id': 'data', 'name': 'Data', 'desc': 'Data line'},
+    )
+    annotations = (
+        ('start-bit', 'Start bit'),
+        ('stop-bit', 'Stop bit'),
+        ('parity-bit', 'Parity bit'),
+        ('word', 'Word')
+    )
+
+    def __init__(self):
+        self.bits = []
+        self.prev_pins = None
+        self.prev_clock = None
+        self.samplenum = 0
+        self.ss_word = None
+        self.clock_was_high = False
+
+    def start(self):
+        self.out_ann = self.register(srd.OUTPUT_ANN)
+
+    def handle_bits(self, datapin):
+        # Ignore non start condition bits (useful during keyboard init).
+        if len(self.bits) == 0 and datapin == 1:
+            return
+
+        # If this is the first bit in a word, save its sample number.
+        if len(self.bits) == 0:
+            self.ss_word = self.samplenum
+
+        self.bits.append(datapin)
+
+        # Find all 11 bits. Start + 8 data + odd parity + stop.
+        if len(self.bits) < 11:
+            return
+
+        # Extract data word.
+        word = 0
+        for i in range(8):
+            word |= (self.bits[i + 1] << i)
+
+        bit_start, bit_stop, bit_parity = self.bits[0], \
+            self.bits[10], self.bits[9]
+
+        bitstring = ''.join([str(i) for i in self.bits])
+        parity_ok = (bin(word).count('1') + bit_parity) % 2 == 1
+
+        if bit_start == 0 and bit_stop == 1 and parity_ok:
+            self.put(self.ss_word, self.samplenum, self.out_ann, [Ann.WORD,
+                     ['OK: %X (%s)' % (word, bitstring)]])
+        else:
+            self.put(self.ss_word, self.samplenum, self.out_ann, [Ann.WORD,
+                     ['Fail: %X (%s)' % (word, bitstring)]])
+
+        self.bits, self.ss_word = [], 0
+
+    def find_clk_edge(self, clock_pin, data_pin):
+        # Ignore sample if the clock pin hasn't changed.
+        if clock_pin == self.prev_clock:
+            return
+        self.prev_clock = clock_pin
+
+        # Sample on falling clock edge.
+        if clock_pin == 1:
+            return
+
+        # Found the correct clock edge, now get the bits.
+        self.handle_bits(data_pin)
+
+    def decode(self, ss, es, data):
+        for (self.samplenum, pins) in data:
+            clock_pin, data_pin = pins[0], pins[1]
+
+            # Ignore identical samples.
+            if self.prev_pins == pins:
+                continue
+            self.prev_pins = pins
+
+            if clock_pin == 0 and not self.clock_was_high:
+                continue
+            self.clock_was_high = True
+
+            self.find_clk_edge(clock_pin, data_pin)