User's Manual

UMXXX
detection; pedometer, step detector and step counter; up to 16 finite state machines
to process
• The LPS22HH barometer interrupt pin is the same as for LSM6DSO: it is an input
pin at boot and must be low so that I2C interface is activated. It can be configured
as push-pull or open-drain after boot. The interrupt pin of this sensor is not
connected to BlueNRG-2.
• The HTS221 relative humidity and temperature interrupt pin is push-pull at boot and
can be reconfigured as open-drain after boot. The interrupt pin of this sensor is not
connected to BlueNRG-2.
• The VL53L1X time-of-flight proximity interrupt line is only open-drain and would
require an external pull-up. The interrupt pin of this sensor is not connected to
BlueNRG-2.
From the application point of view, the dynamic of the environmental parameters is very
slow. Therefore, an interrupt need not be used. The application can wake-up on a regular
basis, every few seconds, perform one-shot measurements with the LPS22HH barometer
or HTS221 relative humidity and temperature sensor, and trigger the corresponding action
if specific conditions are met.
Also, from the application point of view, it is not convenient to keep the VL53L1X proximity
time-of-flight sensor active, waiting for a gesture and a corresponding wake-up interrupt.
The power consumption or the latency would be too high. The power consumption of
VL53L1X ranges from 0.5mA for 1Hz measurements, up to 7mA for 10Hz measurements.
4. BlueNRG-2 features
BlueNRG-2 integrates a Bluetooth Low Energy radio (BLE), an ARM Cortex-M0 core,
12+12kB of RAM, 256kB of Flash memory and several peripherals: SPI (max 1MHz in slave
mode, 8MHz in master mode), 2x I2C (standard 100kHz or fast 400kHz), and UART
interfaces; 2x multi-function timer (MFT), DMA controller, RTC and watchdog, ADC with
PDM stream processor.
The public key cryptography (PKA) and random number generator (RNG) are reserved for
the BLE protocol stack, however the user application can also read the RNG.
The ADC features are: 10-bit, single or continuous acquisition at max 1MHz sampling
frequency, 2x single ended or 1x differential signal (ADC1 and ADC2 pins), embedded
channels for temperature and battery voltage sensing, embedded digital filter with down
sampling. The embedded digital filter can be used to process the PDM stream coming from
a digital MEMS microphone (1.6MHz or 0.8MHz) and convert it to audio PCM (8kHz to
50kHz when 1.6MHz clock is used for the microphone). The BlueNRG-2 sensor node