1 /*
2  * Author: Brendan Le Foll <brendan.le.foll@intel.com>
3  * Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
4  * Copyright (c) 2014 Intel Corporation.
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining
7  * a copy of this software and associated documentation files (the
8  * "Software"), to deal in the Software without restriction, including
9  * without limitation the rights to use, copy, modify, merge, publish,
10  * distribute, sublicense, and/or sell copies of the Software, and to
11  * permit persons to whom the Software is furnished to do so, subject to
12  * the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be
15  * included in all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
21  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
22  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
23  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24  */
25 
26 #include <unistd.h>
27 #include <signal.h>
28 
29 #include "mraa.hpp"
30 #include "math.h"
31 
32 #define MAX_BUFFER_LENGTH 6
33 #define HMC5883L_I2C_ADDR 0x1E
34 
35 // configuration registers
36 #define HMC5883L_CONF_REG_A 0x00
37 #define HMC5883L_CONF_REG_B 0x01
38 
39 // mode register
40 #define HMC5883L_MODE_REG 0x02
41 
42 // data register
43 #define HMC5883L_X_MSB_REG 0
44 #define HMC5883L_X_LSB_REG 1
45 #define HMC5883L_Z_MSB_REG 2
46 #define HMC5883L_Z_LSB_REG 3
47 #define HMC5883L_Y_MSB_REG 4
48 #define HMC5883L_Y_LSB_REG 5
49 #define DATA_REG_SIZE 6
50 
51 // status register
52 #define HMC5883L_STATUS_REG 0x09
53 
54 // ID registers
55 #define HMC5883L_ID_A_REG 0x0A
56 #define HMC5883L_ID_B_REG 0x0B
57 #define HMC5883L_ID_C_REG 0x0C
58 
59 #define HMC5883L_CONT_MODE 0x00
60 #define HMC5883L_DATA_REG 0x03
61 
62 // scales
63 #define GA_0_88_REG 0x00 << 5
64 #define GA_1_3_REG 0x01 << 5
65 #define GA_1_9_REG 0x02 << 5
66 #define GA_2_5_REG 0x03 << 5
67 #define GA_4_0_REG 0x04 << 5
68 #define GA_4_7_REG 0x05 << 5
69 #define GA_5_6_REG 0x06 << 5
70 #define GA_8_1_REG 0x07 << 5
71 
72 // digital resolutions
73 #define SCALE_0_73_MG 0.73
74 #define SCALE_0_92_MG 0.92
75 #define SCALE_1_22_MG 1.22
76 #define SCALE_1_52_MG 1.52
77 #define SCALE_2_27_MG 2.27
78 #define SCALE_2_56_MG 2.56
79 #define SCALE_3_03_MG 3.03
80 #define SCALE_4_35_MG 4.35
81 
82 
83 int running = 0;
84 
85 void
sig_handler(int signo)86 sig_handler(int signo)
87 {
88     if (signo == SIGINT) {
89         printf("closing nicely\n");
90         running = -1;
91     }
92 }
93 
94 int
main()95 main()
96 {
97     float direction = 0;
98     int16_t x = 0, y = 0, z = 0;
99     uint8_t rx_tx_buf[MAX_BUFFER_LENGTH];
100 
101     //! [Interesting]
102     mraa::I2c* i2c;
103     i2c = new mraa::I2c(0);
104 
105     i2c->address(HMC5883L_I2C_ADDR);
106     rx_tx_buf[0] = HMC5883L_CONF_REG_B;
107     rx_tx_buf[1] = GA_1_3_REG;
108     i2c->write(rx_tx_buf, 2);
109     //! [Interesting]
110 
111     i2c->address(HMC5883L_I2C_ADDR);
112     rx_tx_buf[0] = HMC5883L_MODE_REG;
113     rx_tx_buf[1] = HMC5883L_CONT_MODE;
114     i2c->write(rx_tx_buf, 2);
115 
116     signal(SIGINT, sig_handler);
117 
118     while (running == 0) {
119         i2c->address(HMC5883L_I2C_ADDR);
120         i2c->writeByte(HMC5883L_DATA_REG);
121 
122         i2c->address(HMC5883L_I2C_ADDR);
123         i2c->read(rx_tx_buf, DATA_REG_SIZE);
124 
125         x = (rx_tx_buf[HMC5883L_X_MSB_REG] << 8) | rx_tx_buf[HMC5883L_X_LSB_REG];
126         z = (rx_tx_buf[HMC5883L_Z_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Z_LSB_REG];
127         y = (rx_tx_buf[HMC5883L_Y_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Y_LSB_REG];
128 
129         // scale and calculate direction
130         direction = atan2(y * SCALE_0_92_MG, x * SCALE_0_92_MG);
131 
132         // check if the signs are reversed
133         if (direction < 0)
134             direction += 2 * M_PI;
135 
136         printf("Compass scaled data x : %f, y : %f, z : %f\n", x * SCALE_0_92_MG, y * SCALE_0_92_MG,
137                z * SCALE_0_92_MG);
138         printf("Heading : %f\n", direction * 180 / M_PI);
139         sleep(1);
140     }
141     delete i2c;
142 
143     return MRAA_SUCCESS;
144 }
145