Bosch BMP581 - Page 26

Bosch Sensortec"| BST-BMP581-DS004-02 26 | 74
Modifications reserved | Data subject to change
without notice Document number: BST-BMP581-DS004-02
Both interrupts will be asserted at the end of a measurement (when data is ready), when the respective condition is
fulfilled. They will stay asserted as long as the corresponding condition is active. A read of the INT_STATUS register
will not change the FIFO interrupts. FIFO interrupts can only occur if the FIFO is enabled.
If a burst read from the FIFO causes the fill level to drop below the fill level that causes an interrupt, the interrupt will
be deasserted at the end of the burst read.
The FIFO interrupts can be enabled by setting INT_SOURCE.fifo_full_en and INT_SOURCE.fifo_ths_en.
4.7.2.2 Data ready interrupt
The data ready interrupt and status register INT_STATUS.drdy_data_reg is asserted when new pressure and/or
temperature is available in the data registers (see Chapter 3.5 "Data registers"). Also, the new measurement data is
available in the FIFO after the data ready interrupt.
The interrupt can be enabled by setting INT_SOURCE.drdy_data_reg_en.
4.7.2.3 Out-of-range interrupt
The out-of-range (OOR) interrupt is triggered when the pressure value is outside a defined range for a defined number
of samples.
The benefit of this interrupt is that the host system does not need to read the sensor data continously to detect of there
is a significant change of the measured pressure. Instead the host can configure the interrupt, und read sensor data
only if the interrupt triggered.
For the OOR interrupt, the BMP581 checks if the pressure value is within a window around a reference pressure. The
reference pressure can be defined in [Pa] with a width of 17 bit, which covers the complete measurement range of the
sensor. The reference values can be written by access the register fields OOR_CONFIG.oor_thr_p_16,
OOR_THR_P_MSB.oor_thr_p_15_8 and OOR_THR_P_LSB.oor_thr_p_7_0.
The range is also given in [Pa] and can be defined via the register OOR_RANGE.oor_range_p. As the register has a
width of 8bit, the range can span up to +/- 255 Pa around the reference value.
The OOR is out of range if observed pressure P_Pa in is:
_ >  + 
or
_ <   
If one of these conditions is satisfied for the number of samples defined by OOR_CONFIG.cnt_lim, the interrupt will be
triggered.
If subsequent measurements are still out of range, the interrupt will be re-triggered after each of those measurements.
Example. Assumed the user wants to get an interrupt if the pressure is outside the range of 97100 Pa - 97200 Pa. In
this case, the reference should be set to the middle value 97150 Pa, which is 0x17B7E. The window value is half of
the range, which is 50 Pa, or 0x32. This means that the registers need to be set to the following values:
 OOR_CONFIG.oor_thr_p_16 = 0x1
 OOR_THR_P_MSB.oor_thr_p_15_8 = 0x7B
 OOR_THR_P_LSB.oor_thr_p_7_0 = 0x7E
 OOR_RANGE.oor_range_p = 0x32
4.7.2.4 Power-on reset interrupt
The power-on rest (POR) interrupt is triggered each time the BMP581 comes out of a power-up reset. This can
happen if the supply to the device is ramped up, or if the supply was so instable that the BMP581 performed a brown-
out with subsequent power-up reset. The POR interrupt signals that the BMP581 is ready to use.