* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
-#include "i2c.h"
+#include "mraa.h"
#include "math.h"
#define MAX_BUFFER_LENGTH 6
#define HMC5883L_I2C_ADDR 0x1E
-//configuration registers
+// configuration registers
#define HMC5883L_CONF_REG_A 0x00
#define HMC5883L_CONF_REG_B 0x01
-//mode register
+// mode register
#define HMC5883L_MODE_REG 0x02
-//data register
+// data register
#define HMC5883L_X_MSB_REG 0
#define HMC5883L_X_LSB_REG 1
#define HMC5883L_Z_MSB_REG 2
#define HMC5883L_Y_LSB_REG 5
#define DATA_REG_SIZE 6
-//status register
+// status register
#define HMC5883L_STATUS_REG 0x09
-//ID registers
+// 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
+// scales
#define GA_0_88_REG 0x00 << 5
#define GA_1_3_REG 0x01 << 5
#define GA_1_9_REG 0x02 << 5
#define GA_5_6_REG 0x06 << 5
#define GA_8_1_REG 0x07 << 5
-//digital resolutions
+// 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_4_35_MG 4.35
int
-main(int argc, char **argv)
+main(int argc, char** argv)
{
+ mraa_init();
float direction = 0;
int16_t x = 0, y = 0, z = 0;
- char rx_tx_buf[MAX_BUFFER_LENGTH];
+ uint8_t rx_tx_buf[MAX_BUFFER_LENGTH];
- maa_i2c_context *i2c;
- i2c = maa_i2c_init();
+ //! [Interesting]
+ mraa_i2c_context i2c;
+ i2c = mraa_i2c_init(0);
- maa_i2c_address(i2c, HMC5883L_I2C_ADDR);
+ mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
rx_tx_buf[0] = HMC5883L_CONF_REG_B;
rx_tx_buf[1] = GA_1_3_REG;
- maa_i2c_write(i2c, rx_tx_buf, 2);
+ mraa_i2c_write(i2c, rx_tx_buf, 2);
+ //! [Interesting]
- maa_i2c_address(i2c, HMC5883L_I2C_ADDR);
+ mraa_i2c_address(i2c, HMC5883L_I2C_ADDR);
rx_tx_buf[0] = HMC5883L_MODE_REG;
rx_tx_buf[1] = HMC5883L_CONT_MODE;
- maa_i2c_write(i2c, rx_tx_buf, 2);
-
- for(;;) {
- maa_i2c_address(i2c, HMC5883L_I2C_ADDR);
- maa_i2c_write_byte(i2c, HMC5883L_DATA_REG);
-
- maa_i2c_address(i2c, HMC5883L_I2C_ADDR);
- maa_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
+ 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
+ // 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) ;
+ 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);
}
}