MAX6675.cpp

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/* Copyright (c) 2021 Skyward Experimental Rocketry
 * Author: Matteo Pignataro
 *
 * 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
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 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#include "MAX6675.h"
 
#include <drivers/timer/TimestampTimer.h>
 
namespace Boardcore
{
 
MAX6675::MAX6675(SPIBusInterface& bus, miosix::GpioPin cs, SPIBusConfig config)
    : slave(bus, cs, config)
{
}
 
SPIBusConfig MAX6675::getDefaultSPIConfig()
{
    SPIBusConfig spiConfig{};
    spiConfig.clockDivider = SPI::ClockDivider::DIV_32;
    spiConfig.mode         = SPI::Mode::MODE_1;
    return spiConfig;
}
 
bool MAX6675::init() { return true; }
 
bool MAX6675::selfTest() { return true; }
 
bool MAX6675::checkConnection()
{
    uint16_t sample;
 
    {
        SPITransaction spi{slave};
        sample = spi.read16();
    }
 
    // The third bit (D2) indicates whether the thermocouple is connected or not
    // It is high if open
    if ((sample & 0x4) != 0)
    {
        lastError = SensorErrors::SELF_TEST_FAIL;
        LOG_ERR(logger, "Self test failed, the thermocouple is not connected");
        return false;
    }
 
    return true;
}
 
TemperatureData MAX6675::sampleImpl()
{
    uint16_t sample;
 
    {
        SPITransaction spi{slave};
        sample = spi.read16();
    }
 
    TemperatureData result{};
    result.temperatureTimestamp = TimestampTimer::getTimestamp();
 
    // Extract bits 14-3
    sample &= 0x7FF8;
 
    // Convert the integer and decimal part separately
    result.temperature += static_cast<float>(sample >> 3) * 0.25;
 
    return result;
}
 
}  // namespace Boardcore