1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
/*
* Author: Brendan Le Foll <brendan.le.foll@intel.com>
* Copyright (c) 2014 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 <iostream>
#include <string>
#include <stdexcept>
#include <unistd.h>
#include <stdlib.h>
#include <functional>
#include <string.h>
#include "max31855.h"
using namespace upm;
//! [Constructor]
MAX31855::MAX31855(int bus, int cs)
{
// initialise chip select as a normal gpio
if ( !(m_gpio = mraa_gpio_init(cs)) )
{
throw std::invalid_argument(std::string(__FUNCTION__) +
": mraa_gpio_init(cs) failed, invalid pin?");
return;
}
mraa_gpio_dir(m_gpio, MRAA_GPIO_OUT);
// initialise the spi bus with a 2Mhz clock
m_sensor = mraa_spi_init(bus);
mraa_spi_frequency(m_sensor, 2000000);
}
//! [Constructor]
//! [Destructor]
MAX31855::~MAX31855()
{
// close both m_sensor & m_gpio cleanly
mraa_result_t error;
error = mraa_spi_stop(m_sensor);
if (error != MRAA_SUCCESS) {
mraa_result_print(error);
}
error = mraa_gpio_close(m_gpio);
if (error != MRAA_SUCCESS) {
mraa_result_print(error);
}
}
//! [Destructor]
double
MAX31855::getTemp()
{
//! [spi]
// set chip select low
mraa_gpio_write(m_gpio, 0);
uint8_t buf[4];
// set our input buffer to 0, this is clean but not required
memset(buf, 0, sizeof(uint8_t)*4);
// Write buffer to the spi slave
uint8_t* x = mraa_spi_write_buf(m_sensor, buf, 4);
//! [spi]
//! [conversion]
// Endian correct way of making our char array into an 32bit int
int32_t temp = (x[0] << 24) | (x[1] << 16) | (x[2] << 8) | x[3];;
// mraa_spi_write_buf does not free the return buffer
free(x);
if (temp & 0x7) {
std::cerr << "Something went very wrong!" << std::endl;
}
// scrap all the data we dont care about
temp >>= 18;
// LSB = 0.25 degrees C
double c = (double) temp;
c *= 0.25;
//! [conversion]
// set chip select high
mraa_gpio_write(m_gpio, 1);
return c;
}
|
