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      1 /*
      2  * Author: Brendan Le Foll <brendan.le.foll (at) intel.com>
      3  * Author: Thomas Ingleby <thomas.c.ingleby (at) 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
     86 sig_handler(int signo)
     87 {
     88     if (signo == SIGINT) {
     89         printf("closing nicely\n");
     90         running = -1;
     91     }
     92 }
     93 
     94 int
     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