LSM6DSM- Incorrect Accel Data on high ODR using FIFO

[douglasEDM]

Good day, 

I'm currently reading data on the FIFO using Continuous-to-FIFO mode. I'm also using the lsm6dsm_STdC provided on Github. I'm doing the tests using the STEVAL-MKI189V1

I've set up the FIFO to only read Accelerometer data for now. 

While testing, I place the device in three positions, X, Y, Z down respectively.

In the test data: Data0 = X, Data1 = Y and Data2 =Z.

I've set the ODR of the FIFO and Accel to 1k66Hz.

While testing I get the following Results:

X Pointing Down: X reads -1000mG which is expected. But Y and Z jumps between 0 and -1000. Shouldn't they both be 0?

Y Pointing Down: X reads 0 as expected. But Y and Z jumps between 0 and -1000. Shouldn't Z be 0 and Y = -1000?

Z Down: Both X and Y reads 0, but Z jumps between 0 and -1000.

When I set Fifo ODR to 52Hz, everything looks as it should. Why am I getting these results if the ODR is at 1k66Hz?

Regards

Douglas

[Federica Bossi]

Hi @douglasEDM ,

Can you share a reg dump so that I can replicate the test in your same conditions?

Thanks

[douglasEDM]

Hi, 

Do you have any feedback yet?

[douglasEDM]

Hi, 

This is my setup:

 

/* Restore default configuration */
	 lsm6dsm_reset_set(&dev_ctx, PROPERTY_ENABLE);

	 do {
	 lsm6dsm_reset_get(&dev_ctx, &rst);
	 } while (rst);

		/* Set XL full scale and Gyro full scale */
		lsm6dsm_xl_full_scale_set(&dev_ctx, LSM6DSM_16g);
		lsm6dsm_gy_full_scale_set(&dev_ctx, LSM6DSM_125dps);
		/* Enable Block Data Update (BDU) when FIFO support selected */
		lsm6dsm_block_data_update_set(&dev_ctx, PROPERTY_ENABLE);
		/* Set FIFO watermark to a multiple of a pattern
		* in this example we set watermark to 260 pattern
		* which means ten sequence of:
		* (GYRO + XL) = 12 bytes
		*/
		lsm6dsm_fifo_watermark_set(&dev_ctx, 10 * pattern_len);
		lsm6dsm_fifo_stop_on_wtm_set(&dev_ctx, PROPERTY_ENABLE);
		/* Set FIFO mode to Stream to FIFO */
		lsm6dsm_fifo_mode_set(&dev_ctx, LSM6DSM_STREAM_TO_FIFO_MODE);

		/* Enable FIFO watermark interrupt generation on INT1 pin */
		lsm6dsm_pin_int1_route_get(&dev_ctx, &int_1_reg);
		int_1_reg.int1_fth = PROPERTY_ENABLE;
		lsm6dsm_pin_int1_route_set(&dev_ctx, int_1_reg);
		/* FIFO watermark interrupt on INT2 pin */
		//lsm6dsm_pin_int2_route_get(&dev_ctx, &int_2_reg);
		//int_2_reg.int2_fth = PROPERTY_ENABLE;
		//lsm6dsm_pin_int2_route_set(&dev_ctx, int_2_reg);
		/* Set FIFO sensor decimator */
		lsm6dsm_fifo_xl_batch_set(&dev_ctx, LSM6DSM_FIFO_XL_NO_DEC);
		lsm6dsm_fifo_gy_batch_set(&dev_ctx, LSM6DSM_FIFO_GY_NO_DEC);
		/* Set ODR FIFO */
		lsm6dsm_fifo_data_rate_set(&dev_ctx, LSM6DSM_FIFO_1k66Hz);
		/* Set XL and Gyro Output Data Rate:
		* in this example we set 52 Hz for Accelerometer and
		* 52 Hz for Gyroscope
		*/
		lsm6dsm_xl_data_rate_set(&dev_ctx, LSM6DSM_XL_ODR_1k66Hz);
		lsm6dsm_gy_data_rate_set(&dev_ctx, LSM6DSM_GY_ODR_1k66Hz);

 

And this is how I read the values:

if (waterm)
		 {

			HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
			/* Read number of word in FIFO */
			lsm6dsm_fifo_data_level_get(&dev_ctx, &num);
			num_pattern = num / pattern_len;

			while (num_pattern-- > 0)
			{
			 /* Following the sensors ODR configuration, FIFO pattern is composed
			 * by this sequence of samples: GYRO, XL
			 */
			 lsm6dsm_fifo_pattern_get(&dev_ctx, &pattern);
			 lsm6dsm_fifo_raw_data_get(&dev_ctx, data_raw_angular_rate.u8bit, 3 * sizeof(int16_t));
			 angular_rate_dps[0] = lsm6dsm_from_fs125dps_to_mdps(data_raw_angular_rate.i16bit[0])/100;
			 angular_rate_dps[1] = lsm6dsm_from_fs125dps_to_mdps(data_raw_angular_rate.i16bit[1])/100;
			 angular_rate_dps[2] = lsm6dsm_from_fs125dps_to_mdps(data_raw_angular_rate.i16bit[2]/100);
//			 sprintf((char *)tx_buffer, "Angular rate [mdps]:%4.2f\t%4.2f\t%4.2f\r\n",	angular_rate_mdps[0], angular_rate_mdps[1], angular_rate_mdps[2]);
//			 sprintf((char *)tx_buffer, "%4.2f\t%4.2f\t%4.2f\r\n", angular_rate_mdps[0], angular_rate_mdps[1], angular_rate_mdps[2]);

//			 tx_com(tx_buffer, strlen((char const *)tx_buffer));
			 lsm6dsm_fifo_pattern_get(&dev_ctx, &pattern);
			 lsm6dsm_fifo_raw_data_get(&dev_ctx, data_raw_acceleration.u8bit, 3 * sizeof(int16_t));
			 acceleration_mg[0] = lsm6dsm_from_fs16g_to_mg(data_raw_acceleration.i16bit[0]);
			 acceleration_mg[1] = lsm6dsm_from_fs16g_to_mg(data_raw_acceleration.i16bit[1]);
			 acceleration_mg[2] = lsm6dsm_from_fs16g_to_mg(data_raw_acceleration.i16bit[2]);
//			 sprintf((char *)tx_buffer, "Acc [mg]:%4.2f\t%4.2f\t%4.2f\r\n", acceleration_mg[0], acceleration_mg[1], acceleration_mg[2]);
			 sprintf((char *)tx_buffer, "%4.2f\t%4.2f\t%4.2f\t%4.2f\t%4.2f\t%4.2f\r\n", acceleration_mg[0], acceleration_mg[1], acceleration_mg[2], angular_rate_dps[0], angular_rate_dps[1], angular_rate_dps[2]);

			 tx_com(tx_buffer, strlen((char const *)tx_buffer));
			}
			/* Reset FIFO */
			lsm6dsm_fifo_mode_set(&dev_ctx, LSM6DSM_BYPASS_MODE);
			waterm = 0;
			lsm6dsm_fifo_mode_set(&dev_ctx, LSM6DSM_STREAM_TO_FIFO_MODE);
		 }

This code is however for both gyro and accel. I experience the same issue. In this case, at a higher ODR it seems that the Accel follows the same pattern as the Gyro.

Reading the FIFO pattern shows that the correct data pattern is read.