Data Sheet

Read Data Format
For the read operation, two I
2
C operations must be per-
formed. First, the slave ID byte is sent followed by the I
2
C
register that you wish to read. Then a REPEAT START
(Sr) condition is sent, followed by the read slave ID. The
MAX30105 then begins sending data beginning with the
register selected in the first operation. The read pointer
increments automatically, so the MAX30105 continues
sending data from additional registers in sequential order
until a STOP (P) condition is received. The exception to
this is the FIFO_DATA register, at which the read pointer
no longer increments when reading additional bytes. To
read the next register after FIFO_DATA, an I
2
C write
command is necessary to change the location of the read
pointer.
Figure 10 and Figure 11 show the process of reading one
byte or multiple bytes of data.
An initial write operation is required to send the read
register address.
Data is sent from registers in sequential order, starting
from the register selected in the initial I
2
C write operation.
If the FIFO_DATA register is read, the read pointer will not
automatically increment, and subsequent bytes of data
will contain the contents of the FIFO.
Figure 10. Reading one byte of data from MAX30105
Figure 11. Reading multiple bytes of data from the MAX30105
S 1 0 1 0 1 1 1
R/W
= 0
ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
1 0 1 0 1 1 1 ACK D7 D6 D5 D4 D3 D2 D1 D0 NACK
DATA BYTE
P
S = START CONDITION
Sr = REPEATED START CONDITION
P = STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER
NACK = NOT ACKNOWLEDGE
SLAVE ID
REGISTER ADDRESS
Sr
SLAVE ID
R/W
= 1
S 1 0 1 0 1 1 1
R/W
= 0
ACK A7 A6 A5 A4 A3 A2
A1 A0 ACK
1 0 1 0 1 1 1 ACK D7 D6 D5 D4 D3 D2 D1 D0 AM
DATA 1
S = START CONDITION
Sr = REPEATED START CONDITION
P = STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER
AM = ACKNOWLEDGE BY THE MASTER
NACK = NOT ACKNOWLEDGE
SLAVE ID REGISTER ADDRESS
Sr
SLAVE ID
R/W
= 1
D7 D6 D5 D4 D3 D2 D1 AM D7 D6 D5 D4 D3 D2 D1 D0 NACK
DATA n
P
DATA n-1
D0
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Maxim Integrated │ 31
MAX30105 High-Sensitivity Optical Sensor
for Smoke Detection Applications