105 lines
2.6 KiB
C++
105 lines
2.6 KiB
C++
/*
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* \brief I2C LM75A_Soft temperature sensor library (implementation)
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*
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* \author Quentin Comte-Gaz <quentin@comte-gaz.com>
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* \date 8 July 2016 & 14 January 2018
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* \license MIT License (contact me if too restrictive)
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* \copyright Copyright (c) 2016 Quentin Comte-Gaz
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* \version 1.1
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*/
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#include "LM75A_Soft.h"
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#include <SoftwareWire.h>
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namespace LM75A_SoftConstValues
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{
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const int LM75A_Soft_BASE_ADDRESS = 0x48;
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const float LM75A_Soft_DEGREES_RESOLUTION = 0.125;
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const int LM75A_Soft_REG_ADDR_TEMP = 0;
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//const int LM75A_Soft_REG_ADDR_CONF = 1; // Not used for now
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//const int LM57A_REG_ADDR_THYST = 2; // Not used for now
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//const int LM57A_REG_ADDR_TOS = 3; // Not used for now
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}
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using namespace LM75A_SoftConstValues;
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LM75A_Soft::LM75A_Soft(){}
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void LM75A_Soft::begin(int addr, SoftwareWire *theWire)
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{
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_i2c_device_address = addr;
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_wire = theWire;
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_wire->begin();
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}
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float LM75A_Soft::fahrenheitToDegrees(float temperature_in_fahrenheit)
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{
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return ((temperature_in_fahrenheit - 32.0) / 1.8);
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}
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float LM75A_Soft::degreesToFahrenheit(float temperature_in_degrees)
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{
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return ((temperature_in_degrees * 1.8) + 32.0);
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}
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float LM75A_Soft::getTemperatureInFahrenheit() const
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{
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float temperature_in_degrees = getTemperatureInDegrees();
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if (temperature_in_degrees == INVALID_LM75A_Soft_TEMPERATURE) {
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return INVALID_LM75A_Soft_TEMPERATURE;
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}
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return degreesToFahrenheit(temperature_in_degrees);
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}
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float LM75A_Soft::getTemperatureInDegrees() const
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{
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uint16_t real_result = INVALID_LM75A_Soft_TEMPERATURE;
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uint16_t i2c_received = 0;
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// Go to temperature data register
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_wire->beginTransmission(_i2c_device_address);
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_wire->write(LM75A_Soft_REG_ADDR_TEMP);
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if(_wire->endTransmission()) {
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// Transmission error
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return real_result;
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}
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// Get content
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if (_wire->requestFrom(_i2c_device_address, 2)) {
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_wire->readBytes((uint8_t*)&i2c_received, 2);
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} else {
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// Can't read temperature
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return real_result;
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}
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// Modify the value (only 11 MSB are relevant if swapped)
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int16_t refactored_value;
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uint8_t* ptr = (uint8_t*)&refactored_value;
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// Swap bytes
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*ptr = *((uint8_t*)&i2c_received + 1);
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*(ptr + 1) = *(uint8_t*)&i2c_received;
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// Shift data (left-aligned)
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refactored_value >>= 5;
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float real_value;
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if (refactored_value & 0x0400) {
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// When sign bit is set, set upper unused bits, then 2's complement
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refactored_value |= 0xf800;
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refactored_value = ~refactored_value + 1;
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real_value = (float)refactored_value * (-1) * LM75A_Soft_DEGREES_RESOLUTION;
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}
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else {
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real_value = (float)refactored_value * LM75A_Soft_DEGREES_RESOLUTION;
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}
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return real_value;
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}
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