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      1 /*
      2  * Author: Brendan Le Foll <brendan.le.foll (at) intel.com>
      3  * Copyright (c) 2014 Intel Corporation.
      4  *
      5  * Permission is hereby granted, free of charge, to any person obtaining
      6  * a copy of this software and associated documentation files (the
      7  * "Software"), to deal in the Software without restriction, including
      8  * without limitation the rights to use, copy, modify, merge, publish,
      9  * distribute, sublicense, and/or sell copies of the Software, and to
     10  * permit persons to whom the Software is furnished to do so, subject to
     11  * the following conditions:
     12  *
     13  * The above copyright notice and this permission notice shall be
     14  * included in all copies or substantial portions of the Software.
     15  *
     16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     17  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     18  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     19  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
     20  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
     21  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
     22  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
     23  */
     24 
     25 #include <iostream>
     26 #include <string>
     27 #include <stdexcept>
     28 #include <unistd.h>
     29 #include <stdlib.h>
     30 #include <functional>
     31 #include <string.h>
     32 
     33 #include "max31855.h"
     34 
     35 using namespace upm;
     36 
     37 //! [Constructor]
     38 MAX31855::MAX31855(int bus, int cs)
     39 {
     40     // initialise chip select as a normal gpio
     41     if ( !(m_gpio = mraa_gpio_init(cs)) )
     42       {
     43         throw std::invalid_argument(std::string(__FUNCTION__) +
     44                                     ": mraa_gpio_init(cs) failed, invalid pin?");
     45         return;
     46       }
     47     mraa_gpio_dir(m_gpio, MRAA_GPIO_OUT);
     48 
     49     // initialise the spi bus with a 2Mhz clock
     50     m_sensor = mraa_spi_init(bus);
     51     mraa_spi_frequency(m_sensor, 2000000);
     52 }
     53 //! [Constructor]
     54 
     55 //! [Destructor]
     56 MAX31855::~MAX31855()
     57 {
     58     // close both m_sensor & m_gpio cleanly
     59     mraa_result_t error;
     60     error = mraa_spi_stop(m_sensor);
     61     if (error != MRAA_SUCCESS) {
     62         mraa_result_print(error);
     63     }
     64     error = mraa_gpio_close(m_gpio);
     65     if (error != MRAA_SUCCESS) {
     66         mraa_result_print(error);
     67     }
     68 }
     69 //! [Destructor]
     70 
     71 double
     72 MAX31855::getTemp()
     73 {
     74 //! [spi]
     75     // set chip select low
     76     mraa_gpio_write(m_gpio, 0);
     77 
     78     uint8_t buf[4];
     79 
     80     // set our input buffer to 0, this is clean but not required
     81     memset(buf, 0, sizeof(uint8_t)*4);
     82 
     83     // Write buffer to the spi slave
     84     uint8_t* x = mraa_spi_write_buf(m_sensor, buf, 4);
     85 //! [spi]
     86 
     87 //! [conversion]
     88     // Endian correct way of making our char array into an 32bit int
     89     int32_t temp = (x[0] << 24) | (x[1] << 16) | (x[2] << 8) | x[3];;
     90 
     91     // mraa_spi_write_buf does not free the return buffer
     92     free(x);
     93 
     94     if (temp & 0x7) {
     95         std::cerr << "Something went very wrong!" << std::endl;
     96     }
     97 
     98     // scrap all the data we dont care about
     99     temp >>= 18;
    100 
    101     // LSB = 0.25 degrees C
    102     double c = (double) temp;
    103     c *= 0.25;
    104 //! [conversion]
    105 
    106     // set chip select high
    107     mraa_gpio_write(m_gpio, 1);
    108 
    109     return c;
    110 }
    111