User's Manual

UMXXX
AZ-compensated data goes to interrupt logic, while un/filtered OPC-compensated
data goes to FIFO and output registers.
The FIFO buffer can store up to 128 pressure samples (24 bit each) and 128 temperature
samples (16 bit each). FIFO depth can be limited by stopping at the programmable
watermark level. The FIFO can work in the following modes:
• Bypass mode: the FIFO buffer is disabled and cleared.
• FIFO mode: the FIFO buffer collects data until it is full or until the programmed
watermark level is reached, then stops.
• Continuous (or Dynamic Stream) mode: the FIFO buffer collects data continuously,
when it is full or the watermark level is reached, oldest samples are overwritten as
in a circular buffer. The host microcontroller may read the data before it is
overwritten thanks to the FIFO full and FIFO watermark level interrupts.
• Continuous (Dynamic Stream)-to-FIFO mode: the FIFO buffer collects data
continuously but switch to FIFO mode as soon as the selected interrupt occurs.
This mode is especially useful to capture data before and after a specific event.
• Bypass-to-Continuous (Dynamic Stream) mode: the FIFO buffer is disabled but
switch to stream mode as soon as the selected interrupt occurs. This mode is useful
to capture data after an event has occurred.
• Bypass-to-FIFO mode: the FIFO buffer is disabled but switch to FIFO mode as soon
as the selected interrupt occurs. This mode is useful to capture data after an event
has occurred.
LPS22HH vs HTS221 AMBIENT TEMPERATURE MEASUREMENT
The temperature sensor in LPS22HH is designed and used to compensate for temperature
effects in ambient pressure measurements. On the opposite, the temperature sensor in
HTS221 is designed and characterized for ambient temperature measurements.
In the BlueNRG-2 sensor node the ambient temperature is read from HTS221 because of
its higher accuracy and larger range with respect to LPS22HH. If the application needs a
high data rate (above 12.5 Hz), one can use the LPS22HH temperature sensor.
Here is a summary of the characteristics of the embedded temperature sensor:
• LPS22HH: temperature sensor operating range from -40 to +85 Celsius degrees,
sensitivity 100 LSB/degC, temperature absolute accuracy +/-1.5degC (from 0 to 80
Celsius degrees); data rate: 1, 10, 25, 50, 75, 100, 200 Hz.
• HTS221: temperature sensor operating range from -40 to +120 Celsius degrees,
sensitivity 64 LSB/degC, temperature absolute accuracy +/-1degC (from 0 to 60