LSM9DS1 FIFO usage

[Zaren]

Hello,

I tried to use FIFO in way to count data ready . My idea to count sample and if it is a 32 sample in FIFO I read all at once. As far I understand, according by datasheet "

Accelerometer and gyroscope multiple reads (burst)" Page 21

Data stores into FIFO in this way

0, OUT_G_X,OUT_G_Y,OUT_G_Z,OUT_XL_X,OUT_XL_Y,OUT_XL_Z

1, OUT_G_X,OUT_G_Y,OUT_G_Z,OUT_XL_X,OUT_XL_Y,OUT_XL_Z

...

31, OUT_G_X,OUT_G_Y,OUT_G_Z,OUT_XL_X,OUT_XL_Y,OUT_XL_Z

That is my setup of sensor

lsm9ds1_fifo_temp_batch_set(IMU_I2C_ADD, 0);
		lsm9ds1_fifo_mode_set(IMU_I2C_ADD, LSM9DS1_STREAM_MODE);
		lsm9ds1_fifo_stop_on_wtm_set(IMU_I2C_ADD, 28);
 
		pin_cfg.int1_drdy_xl= 0;
		pin_cfg.int1_drdy_g = 1;
		pin_cfg.int1_boot   = 0;
		pin_cfg.int1_fth    = 0;
		pin_cfg.int1_ovr    = 0;
		pin_cfg.int1_fss5   = 0;
		pin_cfg.int1_ig_xl  = 0;
		pin_cfg.int1_ig_g   = 0;
		lsm9ds1_fifo_watermark_set(IMU_I2C_ADD, 32);
		lsm9ds1_fifo_watermark_get(IMU_I2C_ADD, &value);
		lsm9ds1_filter_settling_mask_set(IMU_I2C_ADD, 1);
		lsm9ds1_act_mode_set(IMU_I2C_ADD, 0);

This part of function:

unit8_t size_of_sample 6;
unit8_t gyro_and_accel = 2;
uint8_t samples_count = 32;
 
lsm9ds1_fifo_data_level_get(IMU_I2C_ADD, &unread_samples);
PRINTF("FIFO number of samples %d", unread_samples);
lsm9ds1_read_reg(IMU_I2C_ADD, LSM9DS1_OUT_X_L_G, &data[0],  gyro_and_accel  * size_of_sample  * samples_count) );
lsm9ds1_fifo_data_level_get(IMU_I2C_ADD, &unread_samples);
PRINTF("unread_samples %d", unread_samples);
 

Expected print out :

>> FIFO number of samples 32

>> unread_samples 0

But I got

>> FIFO number of samples 32

>> unread_samples 8

Why it is 8 samples? It should be 0

My I2C works on 400Hz

[TSand.1 · Accepted solution]

Hi, are you working in FIFO mode or in STREAM mode? You should work in FIFO mode. And you can try to set the STOP_ON_FTH bit with threshold 32, even if it is should be no need if you are already in FIFO mode.