Magnetometer Driver

Configuring and reading an LSM303DLHC Magnetometer. More...

Files
file	mag.h
	LSM303DLHC Magnetometer API Header.
file	mag.c
	LSM303DLHC Magnetometer API Implementation.

Macros
#define	MAGREG_CRB   0x01
	Magnetometer Gain Register. More...
#define	MAGREG_MR   0x02
	Magnetometer Mode Register. More...
#define	MAGREG_XH   0x03
	First Magnetometer Output Register. More...

Enumerations
enum	MagRange {   r1g3 = 1, r1g9 = 2, r2g5 = 3, r4g0 = 4,   r4g7 = 5, r5g6 = 6, r8g1 = 7 }
	Magnetometer Range options. More...

Functions
Error	magInit (MagRange r)
	Initialize the Magnetometer. More...
Error	magRead (Vector3f *v)
	Read from the Magnetometer. More...
Error	magWriteRegister (uint8_t reg, uint8_t val)
	Write a Magnetometer Register. More...

Variables
MagRange	magRange
	Stored range to scale returned values. More...

Detailed Description

Configuring and reading an LSM303DLHC Magnetometer.

Macro Definition Documentation

#define MAGREG_CRB   0x01

Magnetometer Gain Register.

Definition at line 48 of file mag.c.

Referenced by magInit().

#define MAGREG_MR   0x02

Magnetometer Mode Register.

Definition at line 49 of file mag.c.

Referenced by magInit().

#define MAGREG_XH   0x03

First Magnetometer Output Register.

Definition at line 50 of file mag.c.

Referenced by magRead().

Enumeration Type Documentation

enum MagRange

Magnetometer Range options.

Enumerator
r1g3	+- 1.3 Gauss
r1g9	+- 1.9 Gauss
r2g5	+- 2.5 Gauss
r4g0	+- 4.0 Gauss
r4g7	+- 4.7 Gauss
r5g6	+- 5.6 Gauss
r8g1	+- 8.1 Gauss

Definition at line 47 of file mag.h.

             {
    r1g3 = 1, 
    r1g9 = 2, 
    r2g5 = 3, 
    r4g0 = 4, 
    r4g7 = 5, 
    r5g6 = 6, 
    r8g1 = 7, 
} MagRange;

Function Documentation

Error magInit

(

MagRange

r

)

Initialize the Magnetometer.

Call before magRead(). I2C should already be initialized!

Parameters

r	MagRange to use.

Returns

TWI_NO_ANSWER, TWI_WRITE_ERROR, ARGUMENT_ERROR or SUCCESS.

Definition at line 77 of file mag.c.

References ARGUMENT_ERROR, magRange, MAGREG_CRB, MAGREG_MR, magWriteRegister(), and SUCCESS.

                          {
    if ((r <= 0) || (r >= 8)) {
        return ARGUMENT_ERROR;
    }
    Error e = magWriteRegister(MAGREG_MR, 0x00); // Continuous Conversion
    if (e != SUCCESS) {
        return e;
    }
    e = magWriteRegister(MAGREG_CRB, (r << 5)); // Set Range
    magRange = r;
    return e;
}

Error magRead

(

Vector3f *

v

)

Read from the Magnetometer.

Magnetometer should already be initialized!

Parameters

v	Vector3f for the read values

Returns

TWI_NO_ANSWER, TWI_WRITE_ERROR, ARGUMENT_ERROR or SUCCESS.

Examples:

hardwareTest.c, and uartFlight.c.

Definition at line 90 of file mag.c.

References ARGUMENT_ERROR, MAG_ADDRESS, magRange, MAGREG_XH, r1g3, r1g9, r2g5, r4g0, r4g7, r5g6, r8g1, SUCCESS, TWI_NO_ANSWER, TWI_READ, TWI_WRITE, TWI_WRITE_ERROR, twiReadAck(), twiReadNak(), twiRepStart(), twiStart(), twiWrite(), Vector3f::x, Vector3f::y, and Vector3f::z.

                           {
    if (v == NULL) {
        return ARGUMENT_ERROR;
    }
    if (twiStart(MAG_ADDRESS | TWI_WRITE)) {
        return TWI_NO_ANSWER;
    }
    if (twiWrite(MAGREG_XH)) {
        return TWI_WRITE_ERROR;
    }
    if (twiRepStart(MAG_ADDRESS | TWI_READ)) {
        return TWI_NO_ANSWER;
    }
    uint8_t xh = twiReadAck();
    uint8_t xl = twiReadAck();
    uint8_t zh = twiReadAck();
    uint8_t zl = twiReadAck();
    uint8_t yh = twiReadAck();
    uint8_t yl = twiReadNak();

    int16_t x = *(int8_t *)(&xh);
    x *= (1 << 8);
    x |= xl;

    int16_t y = *(int8_t *)(&yh);
    y *= (1 << 8);
    y |= yl;

    int16_t z = *(int8_t *)(&zh);
    z *= (1 << 8);
    z |= zl;

    switch (magRange) {
        case r1g3:
            v->x = (((double)x) * 1.3 / MAG_NORMALIZE);
            v->y = (((double)y) * 1.3 / MAG_NORMALIZE);
            v->z = (((double)z) * 1.3 / MAG_NORMALIZE);
            break;
        case r1g9:
            v->x = (((double)x) * 1.9 / MAG_NORMALIZE);
            v->y = (((double)y) * 1.9 / MAG_NORMALIZE);
            v->z = (((double)z) * 1.9 / MAG_NORMALIZE);
            break;
        case r2g5:
            v->x = (((double)x) * 2.5 / MAG_NORMALIZE);
            v->y = (((double)y) * 2.5 / MAG_NORMALIZE);
            v->z = (((double)z) * 2.5 / MAG_NORMALIZE);
            break;
        case r4g0:
            v->x = (((double)x) * 4.0 / MAG_NORMALIZE);
            v->y = (((double)y) * 4.0 / MAG_NORMALIZE);
            v->z = (((double)z) * 4.0 / MAG_NORMALIZE);
            break;
        case r4g7:
            v->x = (((double)x) * 4.7 / MAG_NORMALIZE);
            v->y = (((double)y) * 4.7 / MAG_NORMALIZE);
            v->z = (((double)z) * 4.7 / MAG_NORMALIZE);
            break;
        case r5g6:
            v->x = (((double)x) * 5.6 / MAG_NORMALIZE);
            v->y = (((double)y) * 5.6 / MAG_NORMALIZE);
            v->z = (((double)z) * 5.6 / MAG_NORMALIZE);
            break;
        case r8g1:
            v->x = (((double)x) * 8.1 / MAG_NORMALIZE);
            v->y = (((double)y) * 8.1 / MAG_NORMALIZE);
            v->z = (((double)z) * 8.1 / MAG_NORMALIZE);
            break;
        default:
            return ARGUMENT_ERROR;
    }

    return SUCCESS;
}

Error magWriteRegister	(	uint8_t	reg,
		uint8_t	val
	)

Write a Magnetometer Register.

I2C should aready be initialized!

Parameters

reg	Register Address
val	New Value

Returns

TWI_NO_ANSWER, TWI_WRITE_ERROR or SUCCESS.

Definition at line 63 of file mag.c.

References MAG_ADDRESS, SUCCESS, TWI_NO_ANSWER, TWI_WRITE, TWI_WRITE_ERROR, twiStart(), twiStop(), and twiWrite().

Referenced by magInit().

                                                 {
    if (twiStart(MAG_ADDRESS | TWI_WRITE)) {
        return TWI_NO_ANSWER;
    }
    if (twiWrite(reg)) {
        return TWI_WRITE_ERROR;
    }
    if (twiWrite(val)) {
        return TWI_WRITE_ERROR;
    }
    twiStop();
    return SUCCESS;
}

Variable Documentation

MagRange magRange

Stored range to scale returned values.

Definition at line 54 of file mag.c.

Referenced by magInit(), and magRead().