Added support for PT100 and other RTDs

Added support for RTDs using the MAX31865 interface chip

4 files changed, 411 insertions, 241 deletions

diff --git a/src/Libraries/MAX31855/MAX31855.cpp b/src/Libraries/MAX31855/MAX31855.cpp
deleted file mode 100644
index 7ec6dbd1..00000000
--- a/src/Libraries/MAX31855/MAX31855.cpp
+++ /dev/null
@@ -1,211 +0,0 @@
-#include "MAX31855.h"
-
-// MAX31855 thermocouple chip
-//
-// The MAX31855 continuously samples a Type K thermocouple.  When the MAX31855
-// is selected via its chip select (CS) pin, it unconditionally writes a 32 bit
-// sequence onto the bus.  This sequence is designed such that we need only
-// interpret the high 16 bits in order to ascertain the temperature reading and
-// whether there a fault condition exists.  The low 16 bits provide the
-// MAX31855's cold junction temperature (and thus the board temperature) as
-// well as finer detail on any existing fault condition.
-//
-// The temperature read from the chip is a signed, two's-complement integer.
-// As it is a 14 bit value (in units of one-quarter degrees Celsius), we
-// convert it to a proper signed 16 bit value by adding two high bits.  The
-// high bits added should both be zero if the value is positive (highest bit
-// of the 14 bit value is zero), or both be one if the value is negative
-// (highest bit of the 14 bit value is one).
-//
-// Note Bene: there's a Arduino Due sketch floating about the internet which
-// gets this wrong and for negative temperatures generates incorrect values.
-// E.g, -2047C for what should be -1C; -1798C for what should be -250C.  The
-// values of -1C and -250C are shown as examples in Table 4 of the datasheet
-// for the MAX21855.)  The incorrect Arduino Due sketch appears in, and may be
-// from, the book Arduino Sketches: Tools and Techniques for Programming
-// Wizardry, James A. Langbridge, January 12, 2015, John Wiley & Sons.
-
-// Bits  -- Interpretation
-// -----    -----------------------------------------------------------------
-// 31:18 -- 14 bit, signed thermocouple temperature data.  Units of 0.25 C
-//    17 -- Reserved
-//    16 -- Fault indicator (1 if fault detected; 0 otherwise)
-// 15:04 -- 12 bit, signed cold junction temperature data.  Units of 0.0625 C
-//    03 -- Reserved
-//    02 -- SCV fault; reads 1 if the thermocouple is shorted to Vcc
-//    01 -- SCG fault; reads 1 if the thermocouple is shorted to ground
-//    00 --  OC fault; reads 1 if the thermocouple is not connected (open)
-
-// For purposes of setting bit transfer widths and timings, we need to use a
-// Peripheral Channel Select (PCS).  Use channel #3 as it is unlikely to be
-// used by anything else as the Arduino Due leaves pin 78 unconnected.
-//
-// No warranty given or implied, use at your own risk.
-// dan.newman@mtbaldy.us
-// GPL v3
-
-#define PERIPHERAL_CHANNEL_ID       3
-#define PERIPHERAL_CHANNEL_CS_PIN  78  // NPCS3
-
-// 5.0 MHz Max clock frequency when clocking data out of a MAX31855 
-#define MAX31855_MAX_FREQ 5000000u
-
-// Perform the actual hardware initialization for attaching and using this
-// device on the SPI hardware bus.
-void MAX31855::Init(uint8_t cs)
-{
-	device.csPin = cs;
-	pinMode(cs, OUTPUT);
-	digitalWrite(cs, HIGH);
-
-#ifdef DUET_NG
-	sspi_master_init(&device, 8);
-#else
-	device.id   = PERIPHERAL_CHANNEL_ID;		// Peripheral channel
-	sspi_master_init(&device, 16);
-#endif
-}
-
-MAX31855_error MAX31855::getTemperature(float *t) const
-{
-	if (!sspi_acquire())
-	{
-		return MAX31855_GSPI_BUSY;
-	}
-
-	// Assume properly initialized
-	// Ensure that the configuration is as needed; another GSPI consumer
-	// may have changed the bus speed and/or timing delays.
-	sspi_master_setup_device(&device, SPI_MODE_0, MAX31855_MAX_FREQ);
-
-	// Select the device; enable CS (set it LOW)
-	sspi_select_device(&device);
-	delayMicroseconds(1);		// TODO shorten this (MAX31855 needs 100ns minimum)
-
-	// Read in 32 bits
-
-#ifdef DUET_NG
-	uint8_t dataOut[4] = {0, 0, 0, 0};
-	uint8_t rawBytes[4];
-	spi_status_t sts = sspi_transceive_packet(dataOut, rawBytes, 4);
-	uint16_t raw[2];
-	raw[0] = ((uint16_t)rawBytes[0] << 8) | (uint16_t)rawBytes[1];
-	raw[1] = ((uint16_t)rawBytes[2] << 8) | (uint16_t)rawBytes[3];
-#else
-	uint16_t dataOut[2] = {0, 0};
-	uint16_t raw[2];
-	spi_status_t sts = sspi_transceive_packet16(dataOut, raw, 2);
-#endif
-
-	// Deselect the device; disable CS (set it HIGH)
-	sspi_deselect_device(&device);
-
-	sspi_release();
-
-	if (sts != SPI_OK)
-	{
-		return MAX31855_ERR_TMO;
-	}
-
-	if ((raw[0] & 0x02) || (raw[1] & 0x08))
-	{
-		// These two bits should always read 0
-		// Likely the entire read was 0xFF 0xFF which is not uncommon when first powering up
-		return MAX31855_ERR_IO;
-	}
-
-	// The MAX31855 response is designed such that we can look at
-	// just the high 16 bits and know the temperature and whether
-	// an error occurred.  The low 16 bits contain the cold junction
-	// temperature and finer detail on the nature of any error.
-
-	// We also want to check for three more types of bad reads:
-	//
-	//   1. A read in which the fault indicator bit (16) is set but the fault reason bits (0:2)
-	//      are all clear;
-	//   2. A read in which the fault indicator bit (16) is clear, but one or more of the fault
-	//      reason bits (0:2) are set; and,
-	//   3. A read in which more than one of the fault reason bits (0:1) are set.
-	//
-	// We will perform those three sanity checks as we set the error response code.
-
-	if ((raw[0] & 0x01) || (raw[1] & 0x07))
-	{
-		if (!(raw[0] & 0x01))
-		{
-			// One or more fault reason bits are set but the fault indicator bit is clear?
-			return MAX31855_ERR_IO;
-		}
-
-		// At this point we are assured that bit 16 (fault indicator) is set
-		// and that at least one of the fault reason bits (0:2) are set.  We
-		// now need to ensure that only one fault reason bit is set.
-		uint8_t nbits = 0;
-		MAX31855_error err;
-
-		if (raw[1] & 0x01)
-		{
-			// Open Circuit
-			++nbits;
-			err = MAX31855_ERR_OC;
-		}
-		if (raw[1] & 0x02)
-		{
-			// Short to ground;
-			++nbits;
-			err = MAX31855_ERR_SCG;
-		}
-		if (raw[1] && 0x04)
-		{
-			// Short to Vcc
-			++nbits;
-			err = MAX31855_ERR_SCV;
-		}
-
-		if (nbits == 1)
-		{
-			// Looks like a legitimate error response: bit 16 was set and only one of bits 0:2 was set
-			return err;
-		}
-
-		// Fault indicator was set but a fault reason was not set (nbits == 0) or too
-		// many fault reason bits were set (nbits > 1): assume that a communication error
-		// with the MAX31855 has occurred.
-		return MAX31855_ERR_IO;
-	}
-
-	// Note, the reading is negative if raw[0] & 0x8000 is nonzero
-
-	// Shift the data
-	raw[0] >>= 2;
-	int16_t temp = (int16_t)(raw[0] & 0x3fff);
-
-	// Handle negative temperatures
-	if (raw[0] & 0x2000)
-	{
-		temp |= 0xc000;
-	}
-
-	// And convert to from units of 1/4C to 1C
-	*t = (float)(0.25 * (float)temp);
-
-	// Success!
-	return MAX31855_OK;
-}
-
-const char* MAX31855::errorStr(MAX31855_error err) const
-{
-	switch (err)
-	{
-	default                : return "unknown MAX31855 error";
-	case MAX31855_OK       : return "successful temperature read";
-	case MAX31855_ERR_SCV  : return "thermocouple is shorted to +Vcc";
-	case MAX31855_ERR_SCG  : return "thermocouple is shorted to ground";
-	case MAX31855_ERR_OC   : return "thermocouple is broken (open)";
-	case MAX31855_ERR_TMO  : return "error communicating with MAX31855; read timed out";
-	case MAX31855_ERR_IO   : return "error communicating with MAX31855; disconnected?";
-	case MAX31855_GSPI_BUSY: return "general SPI bus is busy";
-	}
-}
-
-// End
diff --git a/src/Libraries/MAX31855/MAX31855.h b/src/Libraries/MAX31855/MAX31855.h
deleted file mode 100644
index a248a476..00000000
--- a/src/Libraries/MAX31855/MAX31855.h
+++ /dev/null
@@ -1,30 +0,0 @@
-#ifndef MAX31855_H
-#define MAX31855_H
-
-#include "Arduino.h"
-#include "SharedSpi.h"		// for gspi_device
-
-enum MAX31855_error
-{
-	MAX31855_OK      = 0,	// Success
-	MAX31855_ERR_SCV = 1,	// Thermocouple is shorted to Vcc
-	MAX31855_ERR_SCG = 2,	// Thermocouple is shorted to ground
-	MAX31855_ERR_OC  = 3,	// Thermocouple is open
-	MAX31855_ERR_TMO = 4,	// Timeout waiting on I/O (bus busy)
-	MAX31855_ERR_IO  = 5,   // Chip not sending output?  CS not hooked up?
-	MAX31855_GSPI_BUSY		// General SPI bus is busy
-};
-
-class MAX31855
-{
-public:
-	MAX31855() {}
-	MAX31855_error getTemperature(float *temp) const;
-	void Init(uint8_t cs);
-	const char* errorStr(MAX31855_error err) const;
-
-private:
-	sspi_device device;
-};
-
-#endif //MAX31855_H
diff --git a/src/Libraries/TemperatureSensor/TemperatureSensor.cpp b/src/Libraries/TemperatureSensor/TemperatureSensor.cpp
new file mode 100644
index 00000000..266ddd33
--- /dev/null
+++ b/src/Libraries/TemperatureSensor/TemperatureSensor.cpp
@@ -0,0 +1,384 @@
+#include "TemperatureSensor.h"
+#include "RepRapFirmware.h"
+
+// MAX31855 thermocouple chip
+//
+// The MAX31855 continuously samples a Type K thermocouple.  When the MAX31855
+// is selected via its chip select (CS) pin, it unconditionally writes a 32 bit
+// sequence onto the bus.  This sequence is designed such that we need only
+// interpret the high 16 bits in order to ascertain the temperature reading and
+// whether there a fault condition exists.  The low 16 bits provide the
+// MAX31855's cold junction temperature (and thus the board temperature) as
+// well as finer detail on any existing fault condition.
+//
+// The temperature read from the chip is a signed, two's-complement integer.
+// As it is a 14 bit value (in units of one-quarter degrees Celsius), we
+// convert it to a proper signed 16 bit value by adding two high bits.  The
+// high bits added should both be zero if the value is positive (highest bit
+// of the 14 bit value is zero), or both be one if the value is negative
+// (highest bit of the 14 bit value is one).
+//
+// Note Bene: there's a Arduino Due sketch floating about the internet which
+// gets this wrong and for negative temperatures generates incorrect values.
+// E.g, -2047C for what should be -1C; -1798C for what should be -250C.  The
+// values of -1C and -250C are shown as examples in Table 4 of the datasheet
+// for the MAX21855.)  The incorrect Arduino Due sketch appears in, and may be
+// from, the book Arduino Sketches: Tools and Techniques for Programming
+// Wizardry, James A. Langbridge, January 12, 2015, John Wiley & Sons.
+
+// Bits  -- Interpretation
+// -----    -----------------------------------------------------------------
+// 31:18 -- 14 bit, signed thermocouple temperature data.  Units of 0.25 C
+//    17 -- Reserved
+//    16 -- Fault indicator (1 if fault detected; 0 otherwise)
+// 15:04 -- 12 bit, signed cold junction temperature data.  Units of 0.0625 C
+//    03 -- Reserved
+//    02 -- SCV fault; reads 1 if the thermocouple is shorted to Vcc
+//    01 -- SCG fault; reads 1 if the thermocouple is shorted to ground
+//    00 --  OC fault; reads 1 if the thermocouple is not connected (open)
+
+// For purposes of setting bit transfer widths and timings, we need to use a
+// Peripheral Channel Select (PCS).  Use channel #3 as it is unlikely to be
+// used by anything else as the Arduino Due leaves pin 78 unconnected.
+//
+// No warranty given or implied, use at your own risk.
+// dan.newman@mtbaldy.us
+// GPL v3
+
+#define PERIPHERAL_CHANNEL_ID       3
+#define PERIPHERAL_CHANNEL_CS_PIN  78  // NPCS3
+
+const uint32_t MAX31855_Frequency = 4000000;	// maximum for MAX31855 is 5MHz
+const uint32_t MAX31865_Frequency = 4000000;	// maximum for MAX31865 is also 5MHz
+
+// SPI modes:
+// If the inactive state of SCL is LOW (CPOL = 0) (in the case of the MAX31865, this is sampled on the falling edge of CS):
+// The MAX31855 sets up the first data bit after the falling edge of CS, and changes the data on each falling clock edge.
+// So the SAM needs to sample data on the rising clock edge. This requires NCPHA = 1.
+// The MAX31865 changes data after the rising edge of CS, and samples input data on the falling edge.
+// This requires NCPHA = 0.
+
+const uint8_t MAX31855_SpiMode = SPI_MODE_0;
+const uint8_t MAX31865_SpiMode = SPI_MODE_1;
+
+// Define the minimum interval between readings. The MAX31865 needs 62.5ms in 50Hz filter mode.
+const uint32_t MinimumReadInterval = 100;		// minimum interval between reads, in milliseconds
+
+// Table of temperature vs. MAX31865 result for PT100 thermistor, from the MAX31865 datasheet
+struct TempTableEntry
+{
+	int16_t temperature;
+	uint16_t adcReading;
+};
+
+static const TempTableEntry tempTable[] =
+{
+	{-30,	7227},
+	{-20,	7550},
+	{-10,	7871},
+	{0,		8192},
+	{10,	8512},
+	{20,	8830},
+	{30,	9148},
+	{40,	9465},
+	{50,	9781},
+	{60,	10096},
+	{70,	10410},
+	{80,	10723},
+	{90,	11035},
+	{100,	11346},
+	{110,	11657},
+	{120,	11966},
+	{130,	12274},
+	{140,	12582},
+	{150,	12888},
+	{160,	13194},
+	{170,	13498},
+	{180,	13802},
+	{190,	14104},
+	{200,	14406},
+	{225,	15156},
+	{250,	15901},
+	{275,	16639},
+	{300,	17371},
+	{325,	18098},
+	{350,	18818},
+	{375,	19533},
+	{400,	20242},
+	{425,	20945},
+	{450,	21642},
+	{475,	22333},
+	{500,	23018},
+	{525,	23697},
+	{550,	24370}
+};
+
+const size_t NumTempTableEntries = sizeof(tempTable)/sizeof(tempTable[0]);
+
+// Perform the actual hardware initialization for attaching and using this device on the SPI hardware bus.
+void TemperatureSensor::InitThermocouple(uint8_t cs)
+{
+	device.csPin = cs;
+	device.spiMode = MAX31855_SpiMode;
+	device.clockFrequency = MAX31855_Frequency;
+#ifndef DUET_NG
+	device.id = PERIPHERAL_CHANNEL_ID;			// Peripheral channel
+#endif
+	sspi_master_init(&device, 8);
+
+	lastReadingTime = millis();
+	lastResult = TemperatureError::success;
+	lastTemperature = 0.0;
+}
+
+// Perform the actual hardware initialization for attaching and using this device on the SPI hardware bus.
+void TemperatureSensor::InitRtd(uint8_t cs)
+{
+	device.csPin = cs;
+	device.spiMode = MAX31865_SpiMode;
+	device.clockFrequency = MAX31865_Frequency;
+#ifndef DUET_NG
+	device.id = PERIPHERAL_CHANNEL_ID;			// Peripheral channel
+#endif
+	sspi_master_init(&device, 8);
+
+	TemperatureError rslt;
+	for (unsigned int i = 0; i < 3; ++i)		// try 3 times
+	{
+		rslt = TryInitRtd();
+		if (rslt == TemperatureError::success)
+		{
+			break;
+		}
+		delay(MinimumReadInterval);
+	}
+
+	lastReadingTime = millis();
+	lastResult = rslt;
+	lastTemperature = 0.0;
+
+	if (rslt != TemperatureError::success)
+	{
+		reprap.GetPlatform()->MessageF(GENERIC_MESSAGE, "Error: failed to initialise RTD: %s\n", TemperatureErrorString(rslt));
+	}
+}
+
+// Try to initialise the RTD
+TemperatureError TemperatureSensor::TryInitRtd() const
+{
+	// Note that to get the MAX31865 to do continuous conversions, we need to set the bias bit as well as the continuous-conversion bit
+	static const uint8_t modeData[2] = { 0x80, 0xC3 };		// write register 0, bias on, auto conversion, clear errors, 50Hz
+	uint32_t rawVal;
+	TemperatureError sts = DoSpiTransaction(modeData, 2, rawVal);
+
+	if (sts == TemperatureError::success)
+	{
+		static const uint8_t readData[2] = { 0x00, 0x00 };		// read register 0
+		sts = DoSpiTransaction(readData, 2, rawVal);
+	}
+
+	//debugPrintf("Status %d data %04x\n", (int)sts, rawVal);
+	return (sts == TemperatureError::success && (uint8_t)rawVal != 0xC1)
+				? TemperatureError::badResponse
+				: sts;
+}
+
+TemperatureError TemperatureSensor::GetThermocoupleTemperature(float *t)
+{
+	if (inInterrupt() || millis() - lastReadingTime < MinimumReadInterval)
+	{
+		*t = lastTemperature;
+	}
+	else
+	{
+		uint32_t rawVal;
+		TemperatureError sts = DoSpiTransaction(nullptr, 4, rawVal);
+		if (sts != TemperatureError::success)
+		{
+			lastResult = sts;
+		}
+		else
+		{
+			lastReadingTime = millis();
+
+			if ((rawVal & 0x00020008) != 0)
+			{
+				// These two bits should always read 0. Likely the entire read was 0xFF 0xFF which is not uncommon when first powering up
+				lastResult = TemperatureError::ioError;
+			}
+			else if ((rawVal & 0x00010007) != 0)		// check the fault bits
+			{
+				// Check for three more types of bad reads as we set the response code:
+				//   1. A read in which the fault indicator bit (16) is set but the fault reason bits (0:2) are all clear;
+				//   2. A read in which the fault indicator bit (16) is clear, but one or more of the fault reason bits (0:2) are set; and,
+				//   3. A read in which more than one of the fault reason bits (0:1) are set.
+				if ((rawVal & 0x00010000) == 0)
+				{
+					// One or more fault reason bits are set but the fault indicator bit is clear
+					lastResult = TemperatureError::ioError;
+				}
+				else
+				{
+					// At this point we are assured that bit 16 (fault indicator) is set and that at least one of the fault reason bits (0:2) are set.
+					// We now need to ensure that only one fault reason bit is set.
+					uint8_t nbits = 0;
+					if (rawVal & 0x01)
+					{
+						// Open Circuit
+						++nbits;
+						lastResult = TemperatureError::openCircuit;
+					}
+					if (rawVal & 0x02)
+					{
+						// Short to ground;
+						++nbits;
+						lastResult = TemperatureError::shortToGround;
+					}
+					if (rawVal && 0x04)
+					{
+						// Short to Vcc
+						++nbits;
+						lastResult = TemperatureError::shortToVcc;
+					}
+
+					if (nbits != 1)
+					{
+						// Fault indicator was set but a fault reason was not set (nbits == 0) or too many fault reason bits were set (nbits > 1).
+						// Assume that a communication error with the MAX31855 has occurred.
+						lastResult = TemperatureError::ioError;
+					}
+				}
+			}
+			else
+			{
+				rawVal >>= 18;							// shift the 14-bit temperature data to the bottom of the word
+				rawVal |= (0 - (rawVal & 0x2000));		// sign-extend the sign bit
+
+				// And convert to from units of 1/4C to 1C
+				*t = lastTemperature = (float)(0.25 * (float)(int32_t)rawVal);
+				lastResult = TemperatureError::success;
+			}
+		}
+	}
+	return lastResult;
+}
+
+TemperatureError TemperatureSensor::GetRtdTemperature(float *t)
+{
+	if (inInterrupt() || millis() - lastReadingTime < MinimumReadInterval)
+	{
+		*t = lastTemperature;
+	}
+	else
+	{
+		static const uint8_t dataOut[4] = {0, 55, 55, 55};		// read registers 0 (control), 1 (MSB) and 2 (LSB)
+		uint32_t rawVal;
+		TemperatureError sts = DoSpiTransaction(dataOut, 4, rawVal);
+
+		if (sts != TemperatureError::success)
+		{
+			lastResult = sts;
+		}
+		else
+		{
+			lastReadingTime = millis();
+			if (((rawVal & 0x00C10000) != 0xC10000)
+#if 0
+					// We no longer check the error status bit, because it seems to be impossible to clear it once it has been set.
+					// Perhaps we would need to exit continuous reading mode to do so, and then re-enable it afterwards. But this would
+					// take to long.
+#else
+					|| (rawVal & 1) != 0
+#endif
+					)
+			{
+				// Either the continuous conversion bit has got cleared, or the fault bit has been set
+				TryInitRtd();
+				lastResult = TemperatureError::hardwareError;
+			}
+			else
+			{
+				uint16_t adcVal = (rawVal >> 1) & 0x7FFF;
+
+				// Formally-verified binary search routine, adapted from one of the eCv examples
+				size_t low = 0u, high = NumTempTableEntries;
+				while (high > low)
+				//keep(low <= high; high <= NumTempTableEntries)
+				//keep(low == 0u || tempTable[low - 1u].adcReading < adcVal)
+				//keep(high == NumTempTableEntries || adcVal <= tempTable[high].adcReading)
+				//decrease(high - low)
+				{
+					size_t mid = (high - low)/2u + low;			// get the mid point, avoiding arithmetic overflow
+					if (adcVal <= tempTable[mid].adcReading)
+					{
+						high = mid;
+					}
+					else
+					{
+						low = mid + 1u;
+					}
+				}
+				//assert(low <= NumTempTableEntries)
+				//assert(low == 0 || table[low - 1] < adcVal)
+				//assert(low == NumTempTableEntries || adcVal <= table[low])
+
+				if (low == 0)									// if off the bottom of the table
+				{
+					lastResult = TemperatureError::shortCircuit;
+				}
+				else  if (low >= NumTempTableEntries)					// if off the top of the table
+				{
+					lastResult = TemperatureError::openCircuit;
+				}
+				else
+				{
+					const float interpolationFraction = (float)(adcVal - tempTable[low - 1].adcReading)/(float)(tempTable[low].adcReading - tempTable[low - 1].adcReading);
+					*t = lastTemperature = ((float)(tempTable[low].temperature - tempTable[low - 1].temperature) * interpolationFraction)
+							+ (float)tempTable[low - 1].temperature;
+					//debugPrintf("raw %u low %u interp %f temp %f\n", adcVal, low, interpolationFraction, *t);
+					lastResult = TemperatureError::success;
+				}
+			}
+		}
+	}
+	return lastResult;
+}
+
+// Send and receive 1 to 4 bytes of data and return the result as a single 32-bit word
+TemperatureError TemperatureSensor::DoSpiTransaction(const uint8_t dataOut[], size_t nbytes, uint32_t& rslt) const
+{
+	if (!sspi_acquire())
+	{
+		return TemperatureError::busBusy;
+	}
+
+	sspi_master_setup_device(&device);
+	delayMicroseconds(1);
+	sspi_select_device(&device);
+	delayMicroseconds(1);
+
+	uint8_t rawBytes[4];
+	spi_status_t sts = sspi_transceive_packet(dataOut, rawBytes, nbytes);
+
+	delayMicroseconds(1);
+	sspi_deselect_device(&device);
+	delayMicroseconds(1);
+
+	sspi_release();
+
+	if (sts != SPI_OK)
+	{
+		return TemperatureError::timeout;
+	}
+
+	rslt = rawBytes[0];
+	for (size_t i = 1; i < nbytes; ++i)
+	{
+		rslt <<= 8;
+		rslt |= rawBytes[i];
+	}
+
+	return TemperatureError::success;
+}
+
+// End
diff --git a/src/Libraries/TemperatureSensor/TemperatureSensor.h b/src/Libraries/TemperatureSensor/TemperatureSensor.h
new file mode 100644
index 00000000..37b64a3b
--- /dev/null
+++ b/src/Libraries/TemperatureSensor/TemperatureSensor.h
@@ -0,0 +1,27 @@
+#ifndef TEMPERATURESENSOR_H
+#define TEMPERATURESENSOR_H
+
+#include "TemperatureError.h"		// for result codes
+#include "Arduino.h"
+#include "SharedSpi.h"				// for sspi_device
+
+class TemperatureSensor
+{
+public:
+	TemperatureSensor() {}
+	void InitThermocouple(uint8_t cs);
+	void InitRtd(uint8_t cs);
+	TemperatureError GetThermocoupleTemperature(float *temp);
+	TemperatureError GetRtdTemperature(float *temp);
+
+private:
+	TemperatureError DoSpiTransaction(const uint8_t dataOut[], size_t nbytes, uint32_t& rslt) const;
+	TemperatureError TryInitRtd() const;
+
+	sspi_device device;
+	uint32_t lastReadingTime;
+	float lastTemperature;
+	TemperatureError lastResult;
+};
+
+#endif // TEMPERATURESENSOR_H