add a digital multimeter thermocouple

Extend the available temperature sensor with VA18b / PeakTech 3415 DMM.
Based on the code from https://alexkaltsas.wordpress.com/2013/04/19/python-script-to-read-data-from-va18b-multimeter/

config.py.EXAMPLE

@@ -29,15 +29,18 @@ gpio_air  = 9   # Switches 0-phase det. solid-state-relay
 ### Inputs
 gpio_door = 18
 
-### Thermocouple Adapter selection (MAX31855 or MAX6675)
+### Thermocouple Adapter selection (MAX31855 or MAX6675 or VA18B)
 max31855 = 1
 max6675 = 0
+va18b = 0
 
 ### Thermocouple I2C Connection
 gpio_sensor_cs = 27
 gpio_sensor_clock = 22
 gpio_sensor_data = 17
 
+# serial dmm device
+device = '/dev/ttyUSB0'
 
 ########################################################################
 #

lib/oven.py

@@ -10,7 +10,7 @@
 log = logging.getLogger(__name__)
 
 try:
-    if (config.max31855 == config.max6675):
+    if (config.max31855 == config.max6675 == config.va18b):
     	log.error("choose (only) one converter IC")
 	exit()
     if config.max31855:
@@ -19,6 +19,9 @@
     if config.max6675:
    	from max6675 import MAX6675, MAX6675Error
     	log.info("import MAX6675")
+    if config.va18b:
+        from va18b import VA18B
+        log.info("import VA18B")
     sensor_available = True
 except ImportError:
     log.warning("Could not initialize temperature sensor, using dummy values!")
@@ -216,6 +219,9 @@ def __init__(self, time_step):
                                      config.gpio_sensor_clock,
                                      config.gpio_sensor_data,
                                      "c")
+        if config.va18b:
+        	log.info("init DMM VA18B")
+        	self.thermocouple = VA18B(config.device)
 
     def run(self):
         while True:

lib/va18b.py

@@ -0,0 +1,148 @@
+#!/usr/bin/python2.7
+
+#
+#   Just a quick n' dirty script to read the Data from a VA18B multimeter.
+#   This DMM uses the low nibble of 14 bytes to send the lcd segments.
+#
+#       License: GPL v3. http://www.gnu.org/licenses/gpl-3.0-standalone.html
+#
+
+# based on https://alexkaltsas.wordpress.com/2013/04/19/python-script-to-read-data-from-va18b-multimeter/
+
+import signal
+import sys
+import time
+import serial
+import io
+import getopt
+
+class VA18B(object):
+    def __init__(self, device = '/dev/ttyUSB0'):
+        self.device = device
+
+        try:
+            self.port=serial.Serial(port=self.device,
+                       baudrate=2400,
+                       bytesize=serial.EIGHTBITS,
+                       stopbits=serial.STOPBITS_ONE,
+                       parity=serial.PARITY_NONE,
+                       timeout=None)
+
+            if not self.port.isOpen():
+                self.port.open()
+
+        except IOError,err:
+            print '\nError:' + str(err) + '\n'
+            sys.exit(1)
+
+    # Every packet is 14 bytes long.
+    def get_bytes(self):
+        i=0
+        substr=''
+        while i<=13:
+            byte=self.port.read(1)
+            # converting every byte to binary format keeping the low nibble.
+            substr += '{0:08b}'.format(ord(byte))[4:]
+            i += 1
+        return substr
+
+
+    def stream_decode(self, substr):
+
+        ac       = int(substr[0:1])
+        dc       = int(substr[1:2])
+        auto     = int(substr[2:3])
+        pclink   = substr[3:4]
+        minus    = int(substr[4:5])
+
+        digit1   = substr[5:12]
+        dot1     = int(substr[12:13])
+        digit2   = substr[13:20]
+        dot2     = int(substr[20:21])
+        digit3   = substr[21:28]
+        dot3     = int(substr[28:29])
+        digit4   = substr[29:36]
+
+        micro    = int(substr[36:37])
+        nano     = int(substr[37:38])
+        kilo     = int(substr[38:39])
+        diotst   = int(substr[39:40])
+        mili     = int(substr[40:41])
+        percent  = int(substr[41:42])
+        mega     = int(substr[42:43])
+        contst   = int(substr[43:44])
+        cap      = int(substr[44:45])
+        ohm      = int(substr[45:46])
+        rel      = int(substr[46:47])
+        hold     = int(substr[47:48])
+        amp      = int(substr[48:49])
+        volts    = int(substr[49:50])
+        hertz    = int(substr[50:51])
+        lowbat   = int(substr[51:52])
+        minm     = int(substr[52:53])
+        fahrenh  = substr[53:54]
+        celcius  = int(substr[54:55])
+        maxm     = int(substr[55:56])
+
+        digit = {"1111101":"0",
+                 "0000101":"1",
+                 "1011011":"2",
+                 "0011111":"3",
+                 "0100111":"4",
+                 "0111110":"5",
+                 "1111110":"6",
+                 "0010101":"7",
+                 "1111111":"8",
+                 "0111111":"9",
+                 "0000000":"",
+                 "1101000":"L"}
+
+        value = ("-" if minus else " ") +\
+                digit.get(digit1,"") + ("." if dot1 else "") +\
+                digit.get(digit2,"") + ("." if dot2 else "") +\
+                digit.get(digit3,"") + ("." if dot3 else "") +\
+                digit.get(digit4,"")
+
+        flags = " ".join(["AC"         if ac     else "",
+                          "DC"         if dc     else "",
+                          "Auto"       if auto   else "",
+                          "Diode test" if diotst else "",
+                          "Conti test" if contst else "",
+                          "Capacity"   if cap    else "",
+                          "Rel"        if rel    else "",
+                          "Hold"       if hold   else "",
+                          "Min"        if minm   else "",
+                          "Max"        if maxm   else "",
+                          "LowBat"     if lowbat else ""])
+
+        units = ("n"    if nano    else "") +\
+                ("u"    if micro   else "") +\
+                ("k"    if kilo    else "") +\
+                ("m"    if mili    else "") +\
+                ("M"    if mega    else "") +\
+                ("%"    if percent else "") +\
+                ("Ohm"  if ohm     else "") +\
+                ("Amp"  if amp     else "") +\
+                ("Volt" if volts   else "") +\
+                ("Hz"   if hertz   else "") +\
+                ("C"    if celcius else "")
+
+        # print value + " " + flags + " " + units
+        # 020.6   Auto         C
+        return float(value)
+
+    def get(self):
+        self.read()
+        return self.data
+
+    def read(self):
+        substr = self.get_bytes()
+        self.data = self.stream_decode(substr)
+        # print self.data
+        # self.port.flushInput()
+
+class VA18BError(Exception):
+     def __init__(self, value):
+         self.value = value
+     def __str__(self):
+         return repr(self.value)