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
78int
79main(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