/* * 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 "mraa.h" #include "math.h" #define MAX_BUFFER_LENGTH 6 #define HMC5883L_I2C_ADDR 0x1E // configuration registers #define HMC5883L_CONF_REG_A 0x00 #define HMC5883L_CONF_REG_B 0x01 // mode register #define HMC5883L_MODE_REG 0x02 // data register #define HMC5883L_X_MSB_REG 0 #define HMC5883L_X_LSB_REG 1 #define HMC5883L_Z_MSB_REG 2 #define HMC5883L_Z_LSB_REG 3 #define HMC5883L_Y_MSB_REG 4 #define HMC5883L_Y_LSB_REG 5 #define DATA_REG_SIZE 6 // status register #define HMC5883L_STATUS_REG 0x09 // ID registers #define HMC5883L_ID_A_REG 0x0A #define HMC5883L_ID_B_REG 0x0B #define HMC5883L_ID_C_REG 0x0C #define HMC5883L_CONT_MODE 0x00 #define HMC5883L_DATA_REG 0x03 // scales #define GA_0_88_REG 0x00 << 5 #define GA_1_3_REG 0x01 << 5 #define GA_1_9_REG 0x02 << 5 #define GA_2_5_REG 0x03 << 5 #define GA_4_0_REG 0x04 << 5 #define GA_4_7_REG 0x05 << 5 #define GA_5_6_REG 0x06 << 5 #define GA_8_1_REG 0x07 << 5 // digital resolutions #define SCALE_0_73_MG 0.73 #define SCALE_0_92_MG 0.92 #define SCALE_1_22_MG 1.22 #define SCALE_1_52_MG 1.52 #define SCALE_2_27_MG 2.27 #define SCALE_2_56_MG 2.56 #define SCALE_3_03_MG 3.03 #define SCALE_4_35_MG 4.35 int main(int argc, char** argv) { mraa_init(); float direction = 0; int16_t x = 0, y = 0, z = 0; uint8_t rx_tx_buf[MAX_BUFFER_LENGTH]; //! [Interesting] mraa_i2c_context i2c; i2c = mraa_i2c_init(0); mraa_i2c_address(i2c, HMC5883L_I2C_ADDR); rx_tx_buf[0] = HMC5883L_CONF_REG_B; rx_tx_buf[1] = GA_1_3_REG; mraa_i2c_write(i2c, rx_tx_buf, 2); //! [Interesting] mraa_i2c_address(i2c, HMC5883L_I2C_ADDR); rx_tx_buf[0] = HMC5883L_MODE_REG; rx_tx_buf[1] = HMC5883L_CONT_MODE; mraa_i2c_write(i2c, rx_tx_buf, 2); for (;;) { #if 0 int i = 0; //alternative, equivalent method which helps to understand exactly what //the below does mraa_i2c_address(i2c, HMC5883L_I2C_ADDR); for (i = 0; i < DATA_REG_SIZE; i++) { mraa_i2c_read_byte_data(i2c, HMC5883L_DATA_REG+i); } #endif // first 'select' the register we want to read from mraa_i2c_address(i2c, HMC5883L_I2C_ADDR); mraa_i2c_write_byte(i2c, HMC5883L_DATA_REG); // then we read from that register incrementing with every read the // chosen register mraa_i2c_address(i2c, HMC5883L_I2C_ADDR); // this call behaves very similarly to the Wire receive() call mraa_i2c_read(i2c, rx_tx_buf, DATA_REG_SIZE); x = (rx_tx_buf[HMC5883L_X_MSB_REG] << 8) | rx_tx_buf[HMC5883L_X_LSB_REG]; z = (rx_tx_buf[HMC5883L_Z_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Z_LSB_REG]; y = (rx_tx_buf[HMC5883L_Y_MSB_REG] << 8) | rx_tx_buf[HMC5883L_Y_LSB_REG]; // scale and calculate direction direction = atan2(y * SCALE_0_92_MG, x * SCALE_0_92_MG); // check if the signs are reversed if (direction < 0) direction += 2 * M_PI; printf("Compass scaled data x : %f, y : %f, z : %f\n", x * SCALE_0_92_MG, y * SCALE_0_92_MG, z * SCALE_0_92_MG); printf("Heading : %f\n", direction * 180 / M_PI); } }