Modbus

config.py

@@ -99,8 +99,17 @@
 # There are only two breakoutboards supported. 
 #   max31855 - only supports type K thermocouples
 #   max31856 - supports many thermocouples
-max31855 = 1
+max31855 = 0
 max31856 = 0
+modbus = 1
+
+modbus_port_name = "/dev/ttyUSB0"
+modbus_slave_address = 1
+modbus_baudrate = 38400
+modbus_registernumber = 12
+modbus_decimal = 1
+
+
 # uncomment these two lines if using MAX-31856
 import adafruit_max31856
 thermocouple_type = adafruit_max31856.ThermocoupleType.K

lib/oven.py

@@ -83,6 +83,9 @@ def choose_tempsensor(self):
             return Max31855()
         if config.max31856:
             return Max31856()
+        if config.modbus:
+            return Modbus()
+
 
 class SimulatedBoard(Board):
     '''Simulated board used during simulations.
@@ -323,6 +326,40 @@ def raw_temp(self):
                 raise Max31856_Error(k)
         return temp
 
+class Modbus(TempSensorReal):
+    '''each subclass expected to handle errors and get temperature'''
+    def __init__(self):
+        TempSensorReal.__init__(self)
+        log.info("thermocouple modbus")
+        import minimalmodbus
+
+        port = config.modbus_port_name
+        slave = config.modbus_slave_address
+        baudrate = config.modbus_baudrate
+        self.register = config.modbus_registernumber
+        self.decimal = config.modbus_decimal
+
+        self.instrument = minimalmodbus.Instrument(port, slave)
+        self.instrument.serial.baudrate = baudrate
+
+        """
+        if (config.ac_freq_50hz == True):
+            self.thermocouple.noise_rejection = 50
+        else:
+            self.thermocouple.noise_rejection = 60
+        """
+
+    def raw_temp(self):
+        # The underlying adafruit library does not throw exceptions
+        # for thermocouple errors. Instead, they are stored in
+        # dict named self.thermocouple.fault. Here we check that
+        # dict for errors and raise an exception.
+        # and raise Max31856_Error(message)
+
+        temp = self.instrument.read_register(self.register, self.decimal)
+
+        return temp
+
 class Oven(threading.Thread):
     '''parent oven class. this has all the common code
        for either a real or simulated oven'''

requirements.txt

@@ -18,6 +18,8 @@ adafruit-circuitpython-max31856
 # for folks using sw spi (bit banging)
 adafruit-circuitpython-bitbangio
 
+# for folks using modbud input modules
+minimalmodbus
 # untested - for PT100 platinum thermocouples
 #adafruit-circuitpython-max31865
 

test-thermocouple.py

@@ -58,13 +58,30 @@
     print("thermocouple: adafruit max31856")
     sensor = adafruit_max31856.MAX31856(spi, cs)
 
+
+
 print("Degrees displayed in %s\n" % (config.temp_scale))
 
 temp = 0
 while(True):
     time.sleep(1)
     try:
-        temp = sensor.temperature
+        if(config.modbus):
+            import minimalmodbus
+
+            port = config.modbus_port_name
+            slave = config.modbus_slave_address
+            baudrate = config.modbus_baudrate
+            register = config.modbus_registernumber
+            decimal = config.modbus_decimal
+
+            instrument = minimalmodbus.Instrument(port, slave)
+            instrument.serial.baudrate = baudrate
+
+            temp = instrument.read_register(register, decimal)
+        else:
+
+            temp = sensor.temperature
         scale = "C"
         if config.temp_scale == "f":
             temp = temp * (9/5) + 32