Merge pull request #24 from 2bitoperations/MAX38155-kernel-spi

MAX38155 support using kernel SPI drivers

.gitignore

@@ -7,3 +7,4 @@
 thumbs.db
 storage/profiles
 config.py
+.idea/*

README.md

@@ -57,6 +57,10 @@ If you want to deploy the code on a PI for production:
 This **only applies to non-Raspbian installations**, since Raspbian ships
 RPi.GPIO with the default installation.
 
+If you also want to use the in-kernel SPI drivers with a MAX31855 sensor:
+
+    $ sudo pip install Adafruit-MAX31855
+
 ### Clone repo
 
     $ git clone https://github.com/apollo-ng/picoReflow.git

config.py.EXAMPLE

@@ -35,15 +35,25 @@ heater_invert = 0 # switches the polarity of the heater control
 ### Inputs
 gpio_door = 18
 
-### Thermocouple Adapter selection (MAX31855 or MAX6675)
+### Thermocouple Adapter selection:
+#   max31855 - bitbang SPI interface
+#   max31855spi - kernel SPI interface
+#   max6675 - bitbang SPI interface
 max31855 = 1
 max6675 = 0
+max31855spi = 0 # if you use this one, you MUST reassign the default GPIO pins
 
-### Thermocouple I2C Connection
+### Thermocouple Connection (using bitbang interfaces)
 gpio_sensor_cs = 27
 gpio_sensor_clock = 22
 gpio_sensor_data = 17
 
+### Thermocouple SPI Connection (using adafrut drivers + kernel SPI interface)
+spi_sensor_chip_id = 0
+
+### amount of time, in seconds, to wait between reads of the thermocouple
+sensor_time_wait = .5
+
 
 ########################################################################
 #

lib/max31855spi.py

@@ -0,0 +1,36 @@
+#!/usr/bin/python
+import logging
+
+from Adafruit_MAX31855 import MAX31855
+
+class MAX31855SPI(object):
+    '''Python driver for [MAX38155 Cold-Junction Compensated Thermocouple-to-Digital Converter](http://www.maximintegrated.com/datasheet/index.mvp/id/7273)
+     Requires:
+     - adafruit's MAX31855 SPI-only device library
+
+    '''
+    def __init__(self, spi_dev):
+        self.max31855 = MAX31855.MAX31855(spi=spi_dev)
+        self.log = logging.getLogger(__name__)
+
+    def get(self):
+        '''Reads SPI bus and returns current value of thermocouple.'''
+        state = self.max31855.readState()
+        self.log.debug("status %s" % state)
+        if state['openCircuit']:
+            raise MAX31855Error('Not Connected')
+        elif state['shortGND']:
+            raise MAX31855Error('Short to Ground')
+        elif state['shortVCC']:
+            raise MAX31855Error('Short to VCC')
+        elif state['fault']:
+            raise MAX31855Error('Unknown Error')
+        return self.max31855.readLinearizedTempC()
+
+
+class MAX31855SPIError(Exception):
+    def __init__(self, value):
+        self.value = value
+
+    def __str__(self):
+        return repr(self.value)

lib/oven.py

@@ -10,18 +10,31 @@ import config
 log = logging.getLogger(__name__)
 
 try:
-    if (config.max31855 == config.max6675):
+    if config.max31855 + config.max6675 + config.max31855spi > 1:
-    	log.error("choose (only) one converter IC")
+        log.error("choose (only) one converter IC")
-	exit()
+        exit()
     if config.max31855:
-    	from max31855 import MAX31855, MAX31855Error
+        from max31855 import MAX31855, MAX31855Error
-    	log.info("import MAX31855")
+        log.info("import MAX31855")
+    if config.max31855spi:
+        import Adafruit_GPIO.SPI as SPI
+        from max31855spi import MAX31855SPI, MAX31855SPIError
+        log.info("import MAX31855SPI")
+        spi_reserved_gpio = [7, 8, 9, 10, 11]
+        if config.gpio_air in spi_reserved_gpio:
+            raise Exception("gpio_air pin %s collides with SPI pins %s" % (config.gpio_air, spi_reserved_gpio))
+        if config.gpio_cool in spi_reserved_gpio:
+            raise Exception("gpio_cool pin %s collides with SPI pins %s" % (config.gpio_cool, spi_reserved_gpio))
+        if config.gpio_door in spi_reserved_gpio:
+            raise Exception("gpio_door pin %s collides with SPI pins %s" % (config.gpio_door, spi_reserved_gpio))
+        if config.gpio_heat in spi_reserved_gpio:
+            raise Exception("gpio_heat pin %s collides with SPI pins %s" % (config.gpio_heat, spi_reserved_gpio))
     if config.max6675:
-   	from max6675 import MAX6675, MAX6675Error
+        from max6675 import MAX6675, MAX6675Error
-    	log.info("import MAX6675")
+        log.info("import MAX6675")
     sensor_available = True
 except ImportError:
-    log.warning("Could not initialize temperature sensor, using dummy values!")
+    log.exception("Could not initialize temperature sensor, using dummy values!")
     sensor_available = False
 
 try:
@@ -44,7 +57,7 @@ class Oven (threading.Thread):
     STATE_IDLE = "IDLE"
     STATE_RUNNING = "RUNNING"
 
-    def __init__(self, simulate=False, time_step=0.5):
+    def __init__(self, simulate=False, time_step=config.sensor_time_wait):
         threading.Thread.__init__(self)
         self.daemon = True
         self.simulate = simulate
@@ -147,14 +160,14 @@ class Oven (threading.Thread):
             self.heat = 1.0
             if gpio_available:
                if config.heater_invert:
-               	 GPIO.output(config.gpio_heat, GPIO.LOW)
+                 GPIO.output(config.gpio_heat, GPIO.LOW)
                else:
                  GPIO.output(config.gpio_heat, GPIO.HIGH)
         else:
             self.heat = 0.0
             if gpio_available:
                if config.heater_invert:
-               	 GPIO.output(config.gpio_heat, GPIO.HIGH)
+                 GPIO.output(config.gpio_heat, GPIO.HIGH)
                else:
                  GPIO.output(config.gpio_heat, GPIO.LOW)
 
@@ -211,22 +224,29 @@ class TempSensorReal(TempSensor):
     def __init__(self, time_step):
         TempSensor.__init__(self, time_step)
         if config.max6675:
-        	log.info("init MAX6675")
+            log.info("init MAX6675")
-        	self.thermocouple = MAX6675(config.gpio_sensor_cs,
+            self.thermocouple = MAX6675(config.gpio_sensor_cs,
                                      config.gpio_sensor_clock,
                                      config.gpio_sensor_data,
                                      config.temp_scale)
 
         if config.max31855:
-        	log.info("init MAX31855")
+            log.info("init MAX31855")
-        	self.thermocouple = MAX31855(config.gpio_sensor_cs,
+            self.thermocouple = MAX31855(config.gpio_sensor_cs,
                                      config.gpio_sensor_clock,
                                      config.gpio_sensor_data,
                                      config.temp_scale)
 
+        if config.max31855spi:
+            log.info("init MAX31855-spi")
+            self.thermocouple = MAX31855SPI(spi_dev=SPI.SpiDev(port=0, device=config.spi_sensor_chip_id))
+
     def run(self):
         while True:
-            self.temperature = self.thermocouple.get()
+            try:
+                self.temperature = self.thermocouple.get()
+            except Exception:
+                log.exception("problem reading temp")
             time.sleep(self.time_step)