caliper: introduce decoder for cheap generic calipers

2 files changed, 189 insertions, 0 deletions

diff --git a/decoders/caliper/__init__.py b/decoders/caliper/__init__.py
new file mode 100644
index 0000000..3fc99fe
--- /dev/null
+++ b/decoders/caliper/__init__.py
@@ -0,0 +1,36 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2020 Tomas Mudrunka <harvie@github>
+##
+## 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 decodes digital output of cheap generic calipers (usualy made in china)
+Decoder will show measured value in milimeters or inches.
+
+Please note that these devices often communicate on low voltage level,
+which might not be possible to capture with 3.3V logic analyzers.
+So additional circuitry might be needed to capture the signal.
+
+This is NOT for calipers using Digimatic protocol (eg. Mitutoyo and similar brands)
+
+More info:
+
+http://www.shumatech.com/support/chinese_scales.htm
+https://www.instructables.com/id/Reading-Digital-Callipers-with-an-Arduino-USB/
+'''
+
+from .pd import Decoder
diff --git a/decoders/caliper/pd.py b/decoders/caliper/pd.py
new file mode 100644
index 0000000..3db0473
--- /dev/null
+++ b/decoders/caliper/pd.py
@@ -0,0 +1,153 @@
+##
+## This file is part of the libsigrokdecode project.
+##
+## Copyright (C) 2020 Tomas Mudrunka <harvie@github>
+##
+## Permission is hereby granted, free of charge, to any person obtaining a copy
+## of this software and associated documentation files (the "Software"), to deal
+## in the Software without restriction, including without limitation the rights
+## to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+## copies of the Software, and to permit persons to whom the Software is
+## furnished to do so, subject to the following conditions:
+##
+## The above copyright notice and this permission notice shall be included in all
+## copies or substantial portions of the Software.
+##
+## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+## IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+## FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+## AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+## LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+## OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+## SOFTWARE.
+
+import sigrokdecode as srd
+
+class Decoder(srd.Decoder):
+    api_version = 3
+    id = 'caliper'
+    name = 'Caliper'
+    longname = 'Digital calipers'
+    desc = 'Protocol of cheap generic digital calipers'
+    license = 'mit'
+    inputs = ['logic']
+    outputs = []
+    channels = (
+         {'id': 'clk', 'name': 'CLK', 'desc': 'Serial clock line'},
+         {'id': 'data', 'name': 'DATA', 'desc': 'Serial data line'},
+    )
+    options = (
+         {'id': 'timeout_ms', 'desc': 'Timeout packet after X ms, 0 to disable', 'default': 10},
+         {'id': 'unit', 'desc': 'Convert units', 'default': 'keep', 'values': ('keep', 'mm', 'inch')},
+         {'id': 'changes', 'desc': 'Changes only', 'default': 'no', 'values': ('no', 'yes')},
+    )
+    tags = ['Analog/digital', 'IC', 'Sensor']
+    annotations = (
+        ('measurements', 'Measurements'),
+        ('warning', 'Warnings'),
+    )
+    annotation_rows = (
+        ('measurements', 'Measurements', (0,)),
+        ('warnings', 'Warnings', (1,)),
+    )
+
+    def reset_data(self):
+        self.bits = 0
+        self.number = 0
+        self.flags = 0
+
+    def metadata(self, key, value):
+       if key == srd.SRD_CONF_SAMPLERATE:
+            self.samplerate = value
+
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.ss_cmd, self.es_cmd = 0, 0
+        self.reset_data()
+
+    def start(self):
+        self.out_ann = self.register(srd.OUTPUT_ANN)
+
+    #Switch bit order of variable x, which is l bit long
+    def bitr(self,x,l):
+        return int(bin(x)[2:].zfill(l)[::-1], 2)
+
+    def decode(self):
+        self.last_measurement = None
+        while True:
+            clk, data = self.wait([{0: 'r'},{'skip': round(self.samplerate/1000)}])
+            #print([clk,data])
+
+            #Timeout after inactivity
+            if(self.options['timeout_ms'] > 0):
+                if self.samplenum > self.es_cmd + (self.samplerate/(1000/self.options['timeout_ms'])):
+                    if self.bits > 0:
+                        self.put(self.ss_cmd, self.samplenum, self.out_ann, [1, ['timeout with %s bits in buffer'%(self.bits),'timeout']])
+                    self.reset()
+
+            #Do nothing if there was timeout without rising clock edge
+            if self.matched == (False, True):
+                continue
+
+            #Store position of last activity
+            self.es_cmd = self.samplenum
+
+            #Store position of first bit
+            if self.ss_cmd == 0:
+                self.ss_cmd = self.samplenum
+
+            #Shift in measured number
+            if self.bits < 16:
+                self.number = (self.number << 1) | (data & 0b1)
+                self.bits+=1
+                continue
+
+            #Shift in flag bits
+            if self.bits < 24:
+                self.flags = (self.flags << 1) | (data & 0b1)
+                self.bits+=1
+                if self.bits < 24:
+                    continue
+                #Hooray! We got last bit of data
+                self.es_cmd = self.samplenum
+
+            #Do actual decoding
+
+            #print(format(self.flags, '08b'));
+
+            negative = ((self.flags & 0b00001000) >> 3)
+            inch = (self.flags & 0b00000001)
+
+            number = self.bitr(self.number, 16)
+
+            #print(format(number, '016b'))
+
+            if negative > 0:
+                number = -number
+
+            inchmm = 25.4 #how many mms in inch
+
+            if inch:
+                number = number/2000
+                if self.options['unit'] == 'mm':
+                    number *= inchmm
+                    inch = 0
+            else:
+                number = number/100
+                if self.options['unit'] == 'inch':
+                    number = round(number/inchmm,4)
+                    inch = 1
+
+            units = "in" if inch else "mm"
+
+            measurement = (str(number)+units)
+            #print(measurement)
+
+            if ((self.options['changes'] == 'no') or (self.last_measurement != measurement)):
+                self.put(self.ss_cmd, self.es_cmd, self.out_ann, [0, [measurement, str(number)]])
+                self.last_measurement = measurement
+
+            #Prepare for next packet
+            self.reset()