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 "mraa.h"
26 #include "math.h"
27
28 #define MAX_BUFFER_LENGTH 6
29 #define HMC5883L_I2C_ADDR 0x1E
30
31 // configuration registers
32 #define HMC5883L_CONF_REG_A 0x00
33 #define HMC5883L_CONF_REG_B 0x01
34
35 // mode register
36 #define HMC5883L_MODE_REG 0x02
37
38 // data register
39 #define HMC5883L_X_MSB_REG 0
40 #define HMC5883L_X_LSB_REG 1
41 #define HMC5883L_Z_MSB_REG 2
42 #define HMC5883L_Z_LSB_REG 3
43 #define HMC5883L_Y_MSB_REG 4
44 #define HMC5883L_Y_LSB_REG 5
45 #define DATA_REG_SIZE 6
46
47 // status register
48 #define HMC5883L_STATUS_REG 0x09
49
50 // ID registers
51 #define HMC5883L_ID_A_REG 0x0A
52 #define HMC5883L_ID_B_REG 0x0B
53 #define HMC5883L_ID_C_REG 0x0C
54
55 #define HMC5883L_CONT_MODE 0x00
56 #define HMC5883L_DATA_REG 0x03
57
58 // scales
59 #define GA_0_88_REG 0x00 << 5
60 #define GA_1_3_REG 0x01 << 5
61 #define GA_1_9_REG 0x02 << 5
62 #define GA_2_5_REG 0x03 << 5
63 #define GA_4_0_REG 0x04 << 5
64 #define GA_4_7_REG 0x05 << 5
65 #define GA_5_6_REG 0x06 << 5
66 #define GA_8_1_REG 0x07 << 5
67
68 // digital resolutions
69 #define SCALE_0_73_MG 0.73
70 #define SCALE_0_92_MG 0.92
71 #define SCALE_1_22_MG 1.22
72 #define SCALE_1_52_MG 1.52
73 #define SCALE_2_27_MG 2.27
74 #define SCALE_2_56_MG 2.56
75 #define SCALE_3_03_MG 3.03
76 #define SCALE_4_35_MG 4.35
77
78 int
main(int argc,char ** argv)79 main(int argc, char** argv)
80 {
81 mraa_init();
82 float direction = 0;
83 int16_t x = 0, y = 0, z = 0;
84 uint8_t rx_tx_buf[MAX_BUFFER_LENGTH];
85
86 //! [Interesting]
87 mraa_i2c_context i2c;
88 i2c = mraa_i2c_init(0);
89
90 mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
91 rx_tx_buf[0] = HMC5883L_CONF_REG_B;
92 rx_tx_buf[1] = GA_1_3_REG;
93 mraa_i2c_write(i2c, rx_tx_buf, 2);
94 //! [Interesting]
95
96 mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
97 rx_tx_buf[0] = HMC5883L_MODE_REG;
98 rx_tx_buf[1] = HMC5883L_CONT_MODE;
99 mraa_i2c_write(i2c, rx_tx_buf, 2);
100
101 for (;;) {
102 #if 0
103 int i = 0;
104 //alternative, equivalent method which helps to understand exactly what
105 //the below does
106 mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
107 for (i = 0; i < DATA_REG_SIZE; i++) {
108 mraa_i2c_read_byte_data(i2c, HMC5883L_DATA_REG+i);
109 }
110 #endif
111 // first 'select' the register we want to read from
112 mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
113 mraa_i2c_write_byte(i2c, HMC5883L_DATA_REG);
114
115 // then we read from that register incrementing with every read the
116 // chosen register
117 mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
118 // this call behaves very similarly to the Wire receive() call
119 mraa_i2c_read(i2c, rx_tx_buf, DATA_REG_SIZE);
120
121 x = (rx_tx_buf[HMC5883L_X_MSB_REG] << 8) | rx_tx_buf[HMC5883L_X_LSB_REG];
122 z = (rx_tx_buf[HMC5883L_Z_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Z_LSB_REG];
123 y = (rx_tx_buf[HMC5883L_Y_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Y_LSB_REG];
124
125 // scale and calculate direction
126 direction = atan2(y * SCALE_0_92_MG, x * SCALE_0_92_MG);
127
128 // check if the signs are reversed
129 if (direction < 0)
130 direction += 2 * M_PI;
131
132 printf("Compass scaled data x : %f, y : %f, z : %f\n", x * SCALE_0_92_MG, y * SCALE_0_92_MG,
133 z * SCALE_0_92_MG);
134 printf("Heading : %f\n", direction * 180 / M_PI);
135 }
136 }
137