Accelerometer Driver

Configuring and reading an LSM303DLHC Accelerometer. More...

Files
file	acc.h
	LSM303DLHC Accelerometer API Header.
file	acc.c
	LSM303DLHC Accelerometer API Implementation.

Macros
#define	ACCREG_CTRL1   0x20
	Accelerometer Control Register 1. More...
#define	ACCREG_CTRL4   0x23
	Accelerometer Control Register 4. More...
#define	ACCREG_XL   0x28
	First Accelerometer Output Register. More...

Enumerations
enum	AccRange { r2G, r4G, r8G, r16G }
	Accelerometer Range options. More...

Functions
Error	accInit (AccRange r)
	Initialize the Accelerometer. More...
Error	accRead (Vector3f *v)
	Read from the Accelerometer. More...
Error	accWriteRegister (uint8_t reg, uint8_t val)
	Write an Accelerometer Register. More...

Variables
AccRange	accRange
	Stored range to scale returned values. More...

Detailed Description

Configuring and reading an LSM303DLHC Accelerometer.

Macro Definition Documentation

#define ACCREG_CTRL1   0x20

Accelerometer Control Register 1.

Definition at line 49 of file acc.c.

Referenced by accInit().

#define ACCREG_CTRL4   0x23

Accelerometer Control Register 4.

Definition at line 50 of file acc.c.

Referenced by accInit().

#define ACCREG_XL   0x28

First Accelerometer Output Register.

Definition at line 51 of file acc.c.

Referenced by accRead().

Enumeration Type Documentation

enum AccRange

Accelerometer Range options.

Enumerator
r2G	+- 2G
r4G	+- 4G
r8G	+- 8G
r16G	+- 16G

Definition at line 47 of file acc.h.

             {
    r2G, 
    r4G, 
    r8G, 
    r16G, 
} AccRange;

Function Documentation

Error accInit

(

AccRange

r

)

Initialize the Accelerometer.

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

Parameters

r	AccRange to use.

Returns

TWI_NO_ANSWER, TWI_WRITE_ERROR, ARGUMENT_ERROR or SUCCESS.

Definition at line 76 of file acc.c.

References accRange, ACCREG_CTRL1, ACCREG_CTRL4, accWriteRegister(), ARGUMENT_ERROR, r16G, r2G, r4G, r8G, and SUCCESS.

Referenced by orientationInit().

                          {
    uint8_t v;
    switch (r) {
        case r2G:
            v = 0x00;
            break;
        case r4G:
            v = 0x10;
            break;
        case r8G:
            v = 0x20;
            break;
        case r16G:
            v = 0x30;
            break;
        default:
            return ARGUMENT_ERROR;
    }
    accRange = r;
    Error e = accWriteRegister(ACCREG_CTRL1, 0x57); // Enable all axes, 100Hz
    if (e != SUCCESS) {
        return e;
    }
    e = accWriteRegister(ACCREG_CTRL4, v);
    return e;
}

Error accRead

(

Vector3f *

v

)

Read from the Accelerometer.

Accelerometer 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 103 of file acc.c.

References ACC_ADDRESS, ACCFILTERFACTOR, accRange, ACCREG_XL, ARGUMENT_ERROR, r16G, r2G, r4G, r8G, SUCCESS, TWI_NO_ANSWER, TWI_READ, TWI_WRITE, TWI_WRITE_ERROR, twiReadAck(), twiReadNak(), twiRepStart(), twiStart(), twiWrite(), Vector3f::x, Vector3f::y, and Vector3f::z.

Referenced by orientationTask().

                           {
    static double accSumX = 0; /* Buffer for X Low-Pass. */
    static double accSumY = 0; /* Buffer for Y Low-Pass. */
    static double accSumZ = 0; /* Buffer for Z Low-Pass. */
    static double accFilterX = 0; /* Buffer for X Low-Pass. */
    static double accFilterY = 0; /* Buffer for Y Low-Pass. */
    static double accFilterZ = 0; /* Buffer for Z Low-Pass. */

    if (v == NULL) {
        return ARGUMENT_ERROR;
    }
    if (twiStart(ACC_ADDRESS | TWI_WRITE)) {
        return TWI_NO_ANSWER;
    }
    if (twiWrite(ACCREG_XL | (1 << 7))) { // Auto Increment
        return TWI_WRITE_ERROR;
    }
    if (twiRepStart(ACC_ADDRESS | TWI_READ)) {
        return TWI_NO_ANSWER;
    }

    uint8_t xl = twiReadAck();
    uint8_t xh = twiReadAck();
    uint8_t yl = twiReadAck();
    uint8_t yh = twiReadAck();
    uint8_t zl = twiReadAck();
    uint8_t zh = 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 (accRange) {
        case r2G:
            v->x = (((double)x) * 2 / 0x8000);
            v->y = (((double)y) * 2 / 0x8000);
            v->z = (((double)z) * 2 / 0x8000);
            break;
        case r4G:
            v->x = (((double)x) * 4 / 0x8000);
            v->y = (((double)y) * 4 / 0x8000);
            v->z = (((double)z) * 4 / 0x8000);
            break;
        case r8G:
            v->x = (((double)x) * 8 / 0x8000);
            v->y = (((double)y) * 8 / 0x8000);
            v->z = (((double)z) * 8 / 0x8000);
            break;
        case r16G:
            v->x = (((double)x) * 16 / 0x8000);
            v->y = (((double)y) * 16 / 0x8000);
            v->z = (((double)z) * 16 / 0x8000);
            break;
        default:
            return ARGUMENT_ERROR;
    }

    accSumX = accSumX - accFilterX + v->x;
    accFilterX = accSumX / ACCFILTERFACTOR;
    v->x = accFilterX;

    accSumY = accSumY - accFilterY + v->y;
    accFilterY = accSumY / ACCFILTERFACTOR;
    v->y = accFilterY;

    accSumZ = accSumZ - accFilterZ + v->z;
    accFilterZ = accSumZ / ACCFILTERFACTOR;
    v->z = accFilterZ;

    return SUCCESS;
}

Error accWriteRegister	(	uint8_t	reg,
		uint8_t	val
	)

Write an Accelerometer 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 62 of file acc.c.

References TWI_NO_ANSWER.

Referenced by accInit().

                                                 {
    if (twiStart(ACC_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

AccRange accRange

Stored range to scale returned values.

Definition at line 53 of file acc.c.

Referenced by accInit(), and accRead().