Issues working with lis2dh12 in FIFO mode

[Aviv Okon]

Hi

I'm working on a project interfacing the nRF52840 board with the lis2dh12 accelerometer

I'm using SDK 15.3, basing my code on the provided driver and information I've found here

I've used the TWI manager configuration native to the example

the issue I'm encountering is that it seems like the accelerometer stops collecting data after the first time I'm reading from it

the datasheet states that in FIFO mode, it requires a reset to reenable FIFO mode

I thought that calling LIS2DH12_FIFO_CFG and committing the configuration to the device will do the trick, but it doesn't seem to fix the issue

my configuration:

const nrf_drv_twi_config_t twi_instance_config = {
		.scl				= ACC_SCL,
		.sda				= ACC_SDA,
		.frequency			= NRF_DRV_TWI_FREQ_100K,
		.interrupt_priority	= APP_IRQ_PRIORITY_HIGH,
		.clear_bus_init		= false
	};

	errorCode = nrf_twi_mngr_init(&m_nrf_twi_mngr, &twi_instance_config);
	APP_ERROR_CHECK(errorCode);

	errorCode = nrf_twi_sensor_init(&m_nrf_twi_sensor);
	APP_ERROR_CHECK(errorCode);

	errorCode = lis2dh12_init(&m_lis2dh12);
	APP_ERROR_CHECK(errorCode);

	// data acquisition configuration: 100HZ sample rate, low power mode, x axis, y axis, z axis, values in range -2g <-> +2g, disable high resolution mode (in this case step size is 256)
	LIS2DH12_DATA_CFG(m_lis2dh12, LIS2DH12_ODR_100HZ, false, true, true, true, LIS2DH12_SCALE_2G, false);
	errorCode = lis2dh12_cfg_commit(&m_lis2dh12);
	APP_ERROR_CHECK(errorCode);

	// FIFO configuration: enable FIFO, FIFO mode, int1 pin used, 32 values watermark
	LIS2DH12_FIFO_CFG(m_lis2dh12, true, LIS2DH12_FIFO, false, LIS2DH12_MIN_QUEUE_SIZE);
	errorCode = lis2dh12_cfg_commit(&m_lis2dh12);
	APP_ERROR_CHECK(errorCode);

	// interrupt configurataion:
	LIS2DH12_INT1_PIN_CFG(m_lis2dh12, false, enableInterrupts, false, false, false, enableInterrupts, true, false);
	errorCode = lis2dh12_cfg_commit(&m_lis2dh12);
	APP_ERROR_CHECK(errorCode);

and after data read is finished, I'm using the same call to LIS2DH12_FIFO_CFG with the same configuration

Is there something I'm missing here?

Is there any example code working with FIFO mode?

any and all help would be appreciated

[Aviv Okon]

I was able to solve this issue

what I failed to understand was what the watermark interrupt meant. after speaking to a co-worker who used a similar device, we realized that the correct method of operation is to use the watermark interrupt, not the FIFO overrun interrupt. this results in the FIFO never getting full, and thus never needing to be reset

however, this also requires that only a part of the FIFO is read every time, resulting in more frequent interrupts and reads, so this is something to consider

feel free to close this, though if someone would be able to explain how to properly reset the FIFO with the nRF driver, that would also help