Data Sheet

The interrupts are cleared whenever the interrupt status register is read, or when the register that triggered the interrupt
is read. For example, if the particle-sensing sensor triggers an interrupt due to finishing a conversion, reading either the
FIFO data register or the interrupt register clears the interrupt pin (which returns to its normal HIGH state). This also
clears all the bits in the interrupt status register to zero.
Interrupt Enable (0x02–0x03)
Each source of hardware interrupt, with the exception of power ready, can be disabled in a software register within the
MAX30105 IC. The power-ready interrupt cannot be disabled because the digital state of the module is reset upon a
brownout condition (low power supply voltage), and the default condition is that all the interrupts are disabled. Also, it is
important for the system to know that a brownout condition has occurred, and the data within the module is reset as a
result.
The unused bits should always be set to zero for normal operation.
FIFO (0x04–0x07)
FIFO Write Pointer
The FIFO Write Pointer points to the location where the MAX30105 writes the next sample. This pointer advances for each
sample pushed on to the FIFO. It can also be changed through the I
2
C interface when MODE[2:0] is 010, 011, or 111.
FIFO Overow Counter
When the FIFO is full, samples are not pushed on to the FIFO, samples are lost. OVF_COUNTER counts the number
of samples lost. It saturates at 0xF. When a complete sample is “popped” (i.e., removal of old FIFO data and shifting the
samples down) from the FIFO (when the read pointer advances), OVF_COUNTER is reset to zero.
FIFO Read Pointer
The FIFO Read Pointer points to the location from where the processor gets the next sample from the FIFO through the
I
2
C interface. This advances each time a sample is popped from the FIFO. The processor can also write to this pointer
after reading the samples to allow rereading samples from the FIFO if there is a data communication error.
REGISTER B7 B6 B5 B4 B3 B2 B1 B0
REG
ADDR
POR
STATE
R/W
Interrupt
Enable 1
A_
FULL_
EN
DATA_
RDY_EN
ALC_
OVF_EN
PROX_
INT_EN
0x02 0X00 R/W
Interrupt
Enable 2
DIE_TEMP_
RDY_EN
0x03 0x00 R/W
REGISTER B7 B6 B5 B4 B3 B2 B1 B0
REG
ADDR
POR
STATE
R/W
FIFO Write
Pointer
FIFO_WR_PTR[4:0] 0x04 0x00 R/W
Over Flow
Counter
OVF_COUNTER[4:0] 0x05 0x00 R/W
FIFO Read
Pointer
FIFO_RD_PTR[4:0] 0x06 0x00 R/W
FIFO Data
Register
FIFO_DATA[7:0] 0x07 0x00 R/W
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Maxim Integrated │ 14
MAX30105 High-Sensitivity Optical Sensor
for Smoke Detection Applications