--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/max31855.py	Thu Feb 09 00:17:15 2017 +0100
@@ -0,0 +1,96 @@
+import ustruct
+
+
+class MAX31855:
+    """
+    Driver for the MAX31855 thermocouple amplifier.
+
+
+    MicroPython example::
+
+        import max31855
+        from machine import SPI, Pin
+
+        spi = SPI(1, baudrate=1000000)
+        cs = Pin(15, Pin.OUT)
+        s = max31855.MAX31855(spi, cs)
+        print(s.read())
+
+    """
+    def __init__(self, spi, cs):
+        self.spi = spi
+        self.cs = cs
+        self.data = bytearray(4)
+
+    def read(self, internal=False, raw=False):
+        """
+        Read the measured temperature.
+
+        If ``internal`` is ``True``, return a tuple with the measured
+        temperature first and the internal reference temperature second.
+
+        If ``raw`` is ``True``, return the values as 14- and 12- bit integers,
+        otherwise convert them to Celsuius degrees and return as floating point
+        numbers.
+        """
+
+        self.cs.low()
+        try:
+            self.spi.readinto(self.data)
+        finally:
+            self.cs.high()
+        # The data has this format:
+        # 00 --> OC fault
+        # 01 --> SCG fault
+        # 02 --> SCV fault
+        # 03 --> reserved
+        # 04 -. --> LSB
+        # 05  |
+        # 06  |
+        # 07  |
+        #      > reference
+        # 08  |
+        # 09  |
+        # 10  |
+        # 11  |
+        # 12  |
+        # 13  |
+        # 14  | --> MSB
+        # 15 -' --> sign
+        #
+        # 16 --> fault
+        # 17 --> reserved
+        # 18 -.  --> LSB
+        # 19   |
+        # 20   |
+        # 21   |
+        # 22   |
+        # 23   |
+        #       > temp
+        # 24   |
+        # 25   |
+        # 26   |
+        # 27   |
+        # 28   |
+        # 29   |
+        # 30   | --> MSB
+        # 31  -' --> sign
+        if self.data[3] & 0x01:
+            raise RuntimeError("thermocouple not connected")
+        if self.data[3] & 0x02:
+            raise RuntimeError("short circuit to ground")
+        if self.data[3] & 0x04:
+            raise RuntimeError("short circuit to power")
+        if self.data[1] & 0x01:
+            raise RuntimeError("faulty reading")
+        temp, refer = ustruct.unpack('>hh', self.data)
+        refer >>= 4
+        temp >>= 2
+        if raw:
+            if internal:
+                return temp, refer
+            return temp
+        if internal:
+            return temp / 4, refer * 0.0625
+        return temp / 4
+