mcp9808: Initial commit for MCP9808 precision temperature sensor.

Add support for MCP9808 precision temp sensor. Implements all features
except for TCrit and TUpper and TLower locking. Functionality includes
alert, interrupt, resolution and hysteresis control.

Signed-off-by: Marc Graham <marc@m2ag.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/mcp9808/mcp9808.cxx

@@ -0,0 +1,191 @@
+/*
+ * Author: Marc Graham <marc@m2ag.net>
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+
+#include "mcp9808.h"
+#include <cmath>
+
+
+using namespace upm;
+
+MCP9808::MCP9808 (int bus, uint8_t address){
+	m_name = "mcp9808";
+	m_celsius = true;
+	m_tcrit = false;
+	m_tupper = false;
+	m_tlower = false;
+	if(!(i2c = new mraa::I2c(bus))){
+	      throw std::invalid_argument(std::string(__FUNCTION__) +": I2c.init() failed");
+	      return;
+	}
+
+	if((i2c->address(address) != mraa::SUCCESS)){
+	      throw std::invalid_argument(std::string(__FUNCTION__) + ": I2c.address() failed");
+	      return;
+	}
+
+	if(i2c->frequency( mraa::I2C_FAST) != mraa::SUCCESS){
+		throw std::invalid_argument(std::string(__FUNCTION__) + ": I2c.frequency(I2C_STD) failed");
+	    return;
+	}
+}
+
+
+float
+MCP9808::getTemp(){
+	uint16_t result;
+	//Read the register
+	result = i2c->readWordReg(MCP9808_REG_AMBIENT_TEMP);
+	//Swap the bytes
+	result = swapWord(result);
+	//Get the flag bits.
+	m_tcrit = (result & 0x8000) ;
+	m_tupper = (result & 0x4000) ;
+	m_tlower = (result & 0x2000) ;
+	return getTempValue(result);
+}
+
+void
+MCP9808::shutDown(bool sleep){
+	if(sleep) this->updateConfigRegister(MCP9808_CONFIG_SHUTDOWN);
+	 else this->updateConfigRegister(~(MCP9808_CONFIG_SHUTDOWN), false);
+}
+
+
+void
+MCP9808::setMonitorReg(MCP9808_REG reg, float value){
+	uint16_t t;
+	if(m_celsius) t = value * 16.0;
+	 else t = ((value - 32) * 5.0/9.0) * 16.0 ;
+
+	t = swapWord(t);
+
+	if(i2c->writeWordReg(reg, t) != mraa::SUCCESS){
+		throw std::invalid_argument(std::string(__FUNCTION__) + ": I2c.write() failed");
+		return;
+	}
+}
+
+float
+MCP9808::getMonitorReg(MCP9808_REG reg){
+	uint16_t value = i2c->readWordReg(reg);
+	value =  swapWord(value);
+	return getTempValue(value);
+}
+
+
+void
+MCP9808::clearInterrupt(){
+	this->updateConfigRegister(MCP9808_CONFIG_INTCLR);
+}
+
+void
+MCP9808::setAlertMode(uint16_t command){
+	this->updateConfigRegister(command);
+}
+
+void
+MCP9808::clearAlertMode(){
+	//Preserve hysteresis and shutdown settings but
+	//set all alert settings to power on default.
+	this->updateConfigRegister(0x2007, false);
+}
+
+
+void
+MCP9808::setHysteresis(MCP9808_CONFIG value){
+	//Clear hysteresis first.
+	this->updateConfigRegister(0xFFF9, false);
+	this->updateConfigRegister(value);
+}
+
+float
+MCP9808::getHysteresis(){
+	uint16_t value = i2c->readWordReg(MCP9808_REG_CONFIG);
+	value = (value >> 1 ) & 0xF ;
+	float res =  (value == 0) ? 0.0 :  ( 1.5 * pow( 2.0 , value - 1 )) ;
+	return (m_celsius) ? res : res * 9/5;
+}
+
+
+void
+MCP9808::setResolution(MCP9808_RESOLUTION value){
+	if(i2c->writeReg(MCP9808_REG_RESOLUTION, value) != mraa::SUCCESS){
+		  throw std::invalid_argument(std::string(__FUNCTION__) + ": I2c.write() failed");
+		  return;
+	}
+}
+
+float
+MCP9808::getResolution(){
+	uint8_t value = i2c->readReg(MCP9808_REG_RESOLUTION);
+	return   0.5 * (1.0 /  std::pow( 2.0,  value));
+}
+
+
+uint16_t
+MCP9808::getManufacturer(){
+	return swapWord(i2c->readWordReg(MCP9808_REG_MANUF_ID));
+}
+
+uint16_t
+MCP9808::getDevicedId(){
+	return swapWord(i2c->readWordReg(MCP9808_REG_DEVICE_ID));
+}
+
+MCP9808::~MCP9808 (){
+	delete i2c;
+}
+
+
+//Private functions
+
+float
+MCP9808::getTempValue(uint16_t result){
+	bool neg = (result & 0x1000);
+	float res =  (result & 0xFFF) / 16.0;
+	if(neg) res = 0 - ( 256 - res );
+	if(!m_celsius) res = res * 9.0/5.0 + 32;
+	return res;
+}
+
+void
+MCP9808::updateConfigRegister(uint16_t update, bool on){
+	uint16_t reg = i2c->readWordReg(MCP9808_REG_CONFIG);
+	if(on) reg |= update;
+	    else reg &= update;
+
+	if(i2c->writeWordReg(MCP9808_REG_CONFIG, reg) != mraa::SUCCESS){
+		  throw std::invalid_argument(std::string(__FUNCTION__) + ": I2c.write() failed");
+		  return;
+	}
+}
+
+
+uint16_t
+MCP9808::swapWord(uint16_t value){
+	uint16_t res = value;
+	return ((res & 0xFF) << 8) | ((res >> 8 ) & 0xFF);
+}