LSM6DSL partially failling self-tests

[SMari.10]

Hello everyone,

 

I am currently trying to use a LSM6DSL (accelerometer and gyroscope) but only the accelerometer works.

 

I am using a NUCLEO-L476RG with a LSM6DSL from a STEVAL-MKI178V2 with the st library : lsm6dsl.c/h and lsm6dsl_reg.c/h

After the init I get the correct values from the acc but not from the gyro (out of scale values when I am expecting close to 0).

So I have implemented the self tests given int he application notes (attached file) p.96-99.

 

The accelerometer passes its test but not the gyroscope, which have deltas over 300K dps.

 

Here is my gyro's self-test :

 

bool pSensorTask_GYRO_SelfTest(void){
 bool status = false;
 LSM6DSL_Axes_t axes_delta = {0};
 LSM6DSL_Axes_t axes_withoutSelf = {0};
 LSM6DSL_Axes_t axes_withSelf = {0};
 LSM6DSL_AxesRaw_t axes_raw = {0};
 LSM6DSL_Axes_t mAxesRaw_withoutSelf = {0};
 LSM6DSL_Axes_t mAxesRaw_withSelf = {0};
 float sensitivity;
 uint8_t nb_data = 0;
 uint8_t drdy = 0;

 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL1_XL, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL2_G, 0x5c);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL3_C, 0x44);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL4_C, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL5_C, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL6_C, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL7_G, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL8_XL, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL9_XL, 0x00);
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL10_C, 0x00);
 HAL_Delay(150);

 do{
 LSM6DSL_GYRO_Get_DRDY_Status(&MotionSensor, &drdy);
 HAL_Delay(1);
 }while(drdy != true);

 LSM6DSL_GYRO_GetAxesRaw(&MotionSensor, &axes_raw); /* Clear DRDY */

 for(nb_data = 0; nb_data < 5; nb_data++)
 {
 do{
 LSM6DSL_GYRO_Get_DRDY_Status(&MotionSensor, &drdy);
 HAL_Delay(1);
 }while(drdy != true);

 LSM6DSL_GYRO_GetAxesRaw(&MotionSensor, &axes_raw);
 mAxesRaw_withoutSelf.x += axes_raw.x;
 mAxesRaw_withoutSelf.y += axes_raw.y;
 mAxesRaw_withoutSelf.z += axes_raw.z;
 }

 mAxesRaw_withoutSelf.x /= 5;
 mAxesRaw_withoutSelf.y /= 5;
 mAxesRaw_withoutSelf.z /= 5;

 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL5_C, 0x04);
 HAL_Delay(50);

 do{
 LSM6DSL_GYRO_Get_DRDY_Status(&MotionSensor, &drdy);
 HAL_Delay(1);
 }while(drdy != true);

 LSM6DSL_GYRO_GetAxesRaw(&MotionSensor, &axes_raw); /* Clear DRDY */

 for(nb_data = 0; nb_data < 5; nb_data++)
 {
 do{
 LSM6DSL_GYRO_Get_DRDY_Status(&MotionSensor, &drdy);
 HAL_Delay(1);
 }while(drdy != true);

 LSM6DSL_GYRO_GetAxesRaw(&MotionSensor, &axes_raw);
 mAxesRaw_withSelf.x += axes_raw.x;
 mAxesRaw_withSelf.y += axes_raw.y;
 mAxesRaw_withSelf.z += axes_raw.z;
 }

 mAxesRaw_withSelf.x /= 5;
 mAxesRaw_withSelf.y /= 5;
 mAxesRaw_withSelf.z /= 5;

 LSM6DSL_GYRO_GetSensitivity(&MotionSensor, &sensitivity);
 axes_withoutSelf.x = (int32_t)((float)((float)mAxesRaw_withoutSelf.x * sensitivity));
 axes_withoutSelf.y = (int32_t)((float)((float)mAxesRaw_withoutSelf.y * sensitivity));
 axes_withoutSelf.z = (int32_t)((float)((float)mAxesRaw_withoutSelf.z * sensitivity));

 axes_withSelf.x = (int32_t)((float)((float)mAxesRaw_withSelf.x * sensitivity));
 axes_withSelf.y = (int32_t)((float)((float)mAxesRaw_withSelf.y * sensitivity));
 axes_withSelf.z = (int32_t)((float)((float)mAxesRaw_withSelf.z * sensitivity));

 axes_delta.x = axes_withSelf.x - axes_withoutSelf.x;
 axes_delta.y = axes_withSelf.y - axes_withoutSelf.y;
 axes_delta.z = axes_withSelf.z - axes_withoutSelf.z;

 if((abs(axes_delta.x) >= 150) && (abs(axes_delta.x) <= 700) && \
 (abs(axes_delta.y) >= 150) && (abs(axes_delta.y) <= 700) && \
 (abs(axes_delta.z) >= 150) && (abs(axes_delta.z) <= 700))
 {
 status = true;
 }

 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL2_G, 0x00); /* Disable Sensor */
 LSM6DSL_Write_Reg(&MotionSensor, LSM6DSL_CTRL5_C, 0x00); /* Disable self test */

 return status;

}

 

 

I seriously doubt that the hardware is the issue as the acc is perfectly fine.

 

Can anyone help me ?

 

Don't hesitate to ask me if I have forgot any information.

 

Thanks in advance.

 

Regards,

 

MARIE

[SMari.10]

Hi !

I have found the solution.

I had misinterpreted the lsm6 documentation (attached file).

At page 22, the min/max values of the accelerometer are in mg while the gyroscope's one are in dps :

But the returned value from the gyro are in mdps, not dps !

So the comparison of the deltas must be in mdps : 150,000 < deltas < 700,000.

I fixed it in my code and it's now working !