LSM303DLHC outputs frozen

Question

I've was trying all afternoon yesterday to get some data out of my LSM303DLHC using an STM32L152 Nucleo board.

Finally I got all the I2C stuff down, managed to set some registers, verify their contents, etc. so I turned my attention to the data coming out.

No matter what I do it seems, the data is stuck at the same values. When I power cycle the sensor I get changes in the magnetometer values, but then they stay the same until I cycle it again. The outputs from the 3 accelerometer axes are always zero.

I've done a read of the 'block update' register and confirmed the IC it set to do continuous updates.

I have verified on a scope that what I'm receiving is correct to the protocol.

I'm using this breakout board: http://www.aliexpress.com/item/1-pcs-GY-511-LSM303DLHC-Module-E-Compass-3-Axis-Accelerometer-3-Axis-Magnetometer-Module-Sensor/1956617486.html

Any idea anyone? What am I doing wrong here?

#include "mbed.h"

#define ACC_ADDR 0x32
#define MAG_ADDR 0x3C

// ACC registers //
#define CTRL_REG1_A 0x20

#define ACC_X_L 0x28
#define ACC_X_H 0x29
#define ACC_Z_L 0x2C
#define ACC_Z_H 0x2D

// MAG registers //

#define CRA_REG_M 0x00 

#define MAG_X_H 0x03
#define MAG_X_L 0x04

#define MAG_TEMP_H 0x31 
#define MAG_TEMP_L 0x32

//------------------------------------
// Hyperterminal configuration
// 9600 bauds, 8-bit data, no parity
//------------------------------------

Serial pc(SERIAL_TX, SERIAL_RX);

DigitalOut led(LED1);
InterruptIn btn(USER_BUTTON);
I2C i2c(PB_9, PB_8);



int main()
{

    char data_write[2];
    char data_read[6] = {0,0};

    /* Turn on temp sensor */
    data_write[0] = CRA_REG_M ;
    data_write[1] = 0x90;
    int status = i2c.write(MAG_ADDR, data_write, 2, 0);
    if (status != 0) { // Error
        while (1) {
            led = !led;
            wait(0.2);
        }
    }

    int i = 0;
    int bytes = 6;
    int j;

    while (1) {


        // Read acceleromter data registers
        data_write[0] = ACC_X_L;
        i2c.write(ACC_ADDR, data_write, 1, 1); // no stop
        i2c.read(ACC_ADDR, data_read, bytes, 0);

        printf("\f");
        // Display result
        for(j=0;j<bytes;j++){
            printf("d: %x\n", data_read[j]);
        }
        printf("---- (%d)", i++);        

        led = 1;


        wait(0.1);

    }

}

Answer 1

Here is a snippet of my code that sets up the LSM303DLHC

void Sensors::power_up_compass_max_speed()
{
    //Acc 1344Hz ODR, high power, all on
    compass.writeAccReg(LSM303_CTRL_REG1_A, 0b10010111);
    //Acc high res
    compass.writeAccReg(LSM303_CTRL_REG4_A, 0b00001000);
    //Mag continuous conversion
    compass.writeMagReg(LSM303_MR_REG_M, 0x00);
    //Enable mag 220Hz update
    compass.writeMagReg(LSM303_CRA_REG_M, 0b00011100);
}

Port that and see if it works.

Answer 2

Perhaps this suggestion is too late, but it might help others.

I've found that whenever I am implementing a I2c design with a system I have not previously implanted I2C on, it is very helpful to start the development using a serial memory device. This makes testing of the I2C interface much easier.

When testing an I2c interface with a device such as an accelerometer, it is sometimes difficult to tell if the values you read make sense.

With a memory device, you can program a known pattern into the device, then test your I2C read functions by comparing what you read to the pattern you programmed into it.

I've tested my I2C functions by saving a pattern to the memory device, then reading from it for hours at a time ... it gave me much more confidence that my routines were error proof.