1 /*
2 * Author: Brendan Le Foll <brendan.le.foll@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]
MAX31855(int bus,int cs)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]
~MAX31855()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
getTemp()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